The wet synthesis and quantification of ligand-free sub-nanometric Au clusters in solid matrices.

© The Royal Society of Chemistry. The synthesis of ligand-free sub-nanometric metal clusters on a large scale suffers typically from very low yields (15% yields, as unambiguously determined using a very simple and extremely sensitive analytical reaction test.

Solid-state electrochemical characterization of emissions and authorities producing Roman brass coins

[EN] The voltammetry of immobilized particles (VIMP) is applied to describe the solid state electrochemistry of brass. This methodology, which involves sampling at the nanogram level, is applied to discriminate mints/authorities producing different Roman monetary emissions covering since the Republic (88 BCE) to Domitianus (55-96 CE) Upon attachment to graphite electrodes in contact with aqueous acetate buffer at pH 4.75, well defined voltarnmetric responses were obtained centered on Cu- and Zn-localized signals whose intensity can be correlated to EMP data, being sensitive to the contents of Zn (15-30 wt.%) and Sn (0.01-1.1 wt.%). Voltammetric data, combined with ATR-FTIR and FIB-PESEM/EDS…

Homo- and heterobinuclear Cu2+ and Zn2+ complexes of abiotic cyclic hexaazapyridinocyclophanes as SOD mimics

The new receptor 3,7,11,15,19,23-hexaaza-1(2,6)-pyridinacyclotetracosaphane (L1) containing a complete sequence of propylenic chains has been synthesised. The acid–base behaviour and Cu2+ and Zn2+ coordination have been analysed by potentiometric measurements in 0.15 M NaClO4 for L1 and for the related compounds 3,7,11,14,18,22-hexaaza-1(2,6)-pyridinacyclotricosaphane (L2), 3,7,10,13,16,20-hexaaza-1(2,6)-pyridinacycloheneicosaphane (L3) and 3,7,10,12,15,19-hexaaza-1(2,6)-pyridinacycloicosaphane (L4). The crystal structure of [(CuH4L2)(H2O)(ClO4)](ClO4)5·3H2O shows an interesting combination of a metal ion coordinated by the pyridine nitrogen atom and the adjacent amine groups of the chain, …

Electrochemical Monitoring of the Pharmacological Activity of Natural Products

Abstract Electrochemical techniques have largely been applied to characterize the redox reactivity of natural and synthetic compounds and to determine natural and synthetic compounds in solution. A series of new applications of electrochemistry that has emerged in the last few decades and aims to obtain information on the pharmacological activity of natural products is reviewed. Such applications involve the following: (1) electrochemical testing of specific pharmacological activity via electrochemical screening; (2) in situ evaluation of drug–substrate interactions, including the study of pharmacologically active natural products and their metabolites; (3) electrochemical mimicry of select…

On the friction/tangential restitution problem: Independent friction-restitution modeling of sphere rebound with arbitrary spin

Most descriptions of collision events introduce coefficients of friction and tangential restitution which vary significantly with the impact angle, in contrast with the independence of the normal coefficient of restitution with this parameter. A redefinition of the coefficients of friction and tangential restitution based on the idea that friction and restitution effects can be treated as being mutually independent, provides a satisfactory description of experimental data using a ‘constant’ restitution coefficient independent on the impact angle. This independent friction-restitution modeling is developed here for the rebound of a homogeneous sphere having an arbitrary spin on a rough massi…

Analysis of oblique rebound using a redefinition of the coefficient of tangential restitution coefficient

Abstract A redefinition of the coefficient of tangential restitution based on the separation of friction and restitution effects is presented. Using this modified coefficient of tangential restitution and the usual definitions of the coefficients of normal restitution and sliding friction, a description of oblique impacts in both stick and slip regimes is obtained. This, description, which is tested with available rebound data in literature, avoids sharp (apparent) variations in the coefficient tangential restitution with impact angle and can justify anomalous results reported by Calsamiglia et al. (1999) .

Electrochemical Characterization of Egyptian Blue Pigment in Wall Paintings Using the Voltammetry of Microparticles Methodology

The solid state voltammetric response of Egypt blue, Han blue and ploss blue pigments upon attachment to graphite electrodes in contact with aqueous phosphate buffer at pH 7.0 is studied by voltammetry of microparticles and scanning electrochemical microscopy. Such voltammetric responses, combined with those for synthetic specimens consisting of binary mixtures of the pigment and SiO2 or CaCO3 as well as ternary ones of CaCO3 and SiO2 mixtures allow for the identification of the pigment and the support in samples from wall paintings using different electrochemical parameters, in particular upon performing the Tafel and modified Tafel analysis of voltammetric peaks. Identification of Egypt b…

Identification of lipid binders in paintings by gas chromatography

Abstract The influence of the presence and the type of pigments in the lipid binding media of paintings were studied by gas chromatography with flame ionization detector. The drying oils were linseed stand oil, poppy oil and sunflower oil, and the pigments studied were cadmium red, cobalt blue, tin white, lead white, chalk and plaster of Paris, commonly used in paintings. The results indicate that the stearic/palmitic ratio and the presence of pigments are quite stable during ageing. However, some differences in the oleic acid/palmitic acid ratio were found, depending on the type of pigment present in the lipid binding media. These variations are related to the drying effect of the pigments…

An authentication case study: Antonio Palomino versus Vicente Guillo paintings in the vaulted ceiling of the Sant Joan del Mercat church (Valencia, Spain)

In 1695, the Valencian artist Vicente Guillo was engaged in painting the vault of the Sant Joan del Mercat church in Valencia, Spain. After preliminary work was carried out, his contract was cancelled. In 1697, Antonio Palomino, renowned for the publication of his technical treatise entitled El Museo Pictorio y Escala Optica, was finally selected as the painter in charge of decorating the vaulted ceiling of Sant Joan del Mercat. This paper reports an analytical study focused on the characterisation and discrimination of the palette and painting procedures used by Palomino and Guillo in the frescoes of Sant Joan del Mercat. For this purpose, Raman spectroscopy combined with light microscopy,…

Square wave voltammetric determination of the redox state of a reversibly oxidized/reduced depolarizer in solution and in solid state

Abstract Square wave voltammetric measurements allows for determining the composition of system containing a reversibly reducible/oxidable electroactive species in two oxidation states. The method is based on recording the ratio of reverse to forward peak currents. That ratio can be correlated with the molar fraction of the oxidized (or reduced) form of the depolarizer. The method was compared with cyclic voltammetric methods suggested in literature and it was tested using Fe ( CN ) 6 3 - / Fe ( CN ) 6 4 - in solution phase. Application to solid state systems is illustrated by the dehydroindigo/indigo couple in synthetic Maya Blue-type specimens prepared from indigo plus different clays whe…

Electrochemical characterization of natural gold samples using the voltammetry of immobilized particles

The application of the voltammetry of immobilized particles for characterizing natural gold samples from different geological settings and dating vein deposits is described. This is based on recording characteristic electrochemical oxidation signatures of gold and silver following the attachment of metal sub-microsamples to graphite electrodes. Keywords: Electrochemistry, Gold, Mineralogy, Placer deposits, Vein deposits, Nuggets

Electrochemical monitoring of ROS influence on seedlings and germination response to salinity stress of three species of the tribe Inuleae.

Solid-state electrochemical methods have been applied to the establishment of patterns of plant growth and response to saline stress using seedlings of Inula helenium L., Dittrichia viscosa (L.) Greuter (Inula viscosa (L.) Aiton), Limbarda crithmoides (L.) Dumort (Inula crithmoides L.). Upon in situ electrochemical generation of reactive oxygen species (ROS) the reactivity with such species was monitored using voltammetric signals associated to the oxidation of polyphenolic components of the plants. A simple kinetic model based on second-order reaction between ROS and polyphenolic components is applied to electrochemical data yielding apparent rate constants which can be correlated with the…

Few layer 2D pnictogens catalyze the alkylation of soft nucleophiles with esters

Group 15 elements in zero oxidation state (P, As, Sb and Bi), also called pnictogens, are rarely used in catalysis due to the difficulties associated in preparing well–structured and stable materials. Here, we report on the synthesis of highly exfoliated, few layer 2D phosphorene and antimonene in zero oxidation state, suspended in an ionic liquid, with the native atoms ready to interact with external reagents while avoiding aerobic or aqueous decomposition pathways, and on their use as efficient catalysts for the alkylation of nucleophiles with esters. The few layer pnictogen material circumvents the extremely harsh reaction conditions associated to previous superacid–catalyzed alkylations…

Sequential identification of organic dyes using the voltammetry of microparticles approach

An electrochemical method for identifying indigoid, anthraquinonic, naphtoquinonic, flavonoid, pyrone, pyran, and other related dyes in microsamples from works of art is reported using the voltammetry of microparticles methodology. Products of solid state oxidation/reduction of dyes form a layer on the lateral faces of the dye crystals as suggested by ATR-FTIR and AFM data. This method is based on the sequential application of oxidative and reductive constant-potential polarization steps coupled with the record of square wave voltammograms to solid microsamples of dyes in contact with aqueous electrolytes.

Marine inspired antiplasmodial thiazinoquinones: synthesis, computational studies and electrochemical assays

In the search for new antimalarials, we used the quinone scaffold of marine secondary metabolites as a chemical starting point to synthesize new thiazinoquinone compounds. Most of synthetic derivatives have shown a significant pharmacological activity and some structural requirements, critical for both the antiplasmodial effect and cytotoxicity, have been evidenced. The redox properties of the prepared compounds have been investigated by computational studies and electrochemical assays, which indicated that a higher antiplasmodial activity of some thiazinoquinones is related to their greater ability to form the semiquinone species and strongly interact with free Fe(III)-protoporphyrin IX.

Independent friction-restitution modeling of two-disk collisions

[EN] The oblique collisions between two axisymmetric disks moving on a flat horizontal surface are described in terms of impact modeling based on the assumption that normal and tangential restitution mechanisms operate independently of friction. Describing these mechanisms in terms of the usual Coulomb formulation, the model allows for an interpretation of some ¿anomalous¿ experimental data reported in the literature. These experimental data, corresponding to the variation of the coefficients of friction and tangential restitution with the impact angle, remained unexplained in classic formulations, are understood within the framework of the independent friction-restitution closure. Experime…

Characterization of Iranian Moarraque glazes by light microscopy, SEM-EDX and voltammetry of microparticles

Abstract Glazed ceramics have been traditionally used in Iran for decorating mosques and some civil historical buildings. In particular, Moarraque glazes have been extensively used in the indoor and outdoor decoration of mosques in Iran since the middle 14th century. The pieces have a complex elaboration based on a main glazed piece corresponding to the skeleton structure of the Shah Abbasi flower, which contains a number of holes, where are placed, mosaic-like, smaller glazed pieces forming a compact and single tile. The present work describes the analytical study performed on the glazes of several pieces of Moarraque tiles from the Ali Ebn Abi Taleb Mosque (Esfahan, Iran), which date back…

In vivo Electrochemical Monitoring of Signaling Transduction of Plant Defense Against Stress in Leaves of Aloe vera L.

Characterization of prehispanic cosmetics found in a burial of the ancient city of Teotihuacan (Mexico)

The present paper reports the chemical data obtained on samples of pigmenting materials contained in 31 miniature vessels found in a burial found in Teopancazco, a multiethnic neighborhood center located in the southeastern sector of the archaeological site of Teotihuacan (Central Mexico) and the analytical protocol established for the complete characterization of these archaeological materials. For this purpose a multi-technique approach based on the combination of several non destructive and micro-destructive instrumental techniques, namely, light microscopy (LM), scanning electron microscopy-X-ray micro-analysis (SEMe EDX), transmission electron microscopy (TEM), voltammetry of micropart…

Solid state electrochemical behavior of organosulfur compounds

Abstract The solid-sate electrochemistry of organosulfur compounds existing in petroleum and its derived matrices is described using the voltammetry of immobilized microparticles methodology. Cyclic and square wave voltammogrammetric responses of sulfur compounds responsible of aging of asphalt pavements, namely, thiophenes, disulfides, sulfides, sulfoxides and sulfones were determined at compound-modified graphite electrodes in contact with 0.10 M H2SO4. The electrochemical oxidation/reduction products were characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy with energy dispersion x-ray detection (SEM-EDX) couple…

Unconventional Fluorescence Quenching in Naphthalimide-Capped CdSe/ZnS Nanoparticles

Core–shell (CS) CdSe/ZnS quantum dots (QD) capped with ligands that possess a mercapto or an amino group and a naphthalimide (NI) as chromophore unit, linked by a short ethylene chain (CS@S–NI and CS@H2N–NI, respectively), have been synthesized and fully characterized by infrared and nuclear magnetic resonance spectroscopies, high-resolution transmission electron microscopy, and voltammetry as well as by steady-state absorption and emission spectroscopies. The organic ligands HS–NI and H2N–NI act as bidentate ligands, thereby causing a drastic decrease in the QD emission. This was particularly evident in the case of CS@S–NI. This behavior has been compared with that of commercially availabl…

H-Point Standard Addition Method Applied to Voltammetry of Microparticles. Quantitation of Dyes in Pictorial Samples

A solid-state electrochemical application of the H-point standard addition method (HPSAM) for quantifying two electroactive compounds, A, B, that produce strongly overlapped voltammetric peaks is described. It is based on peak current measurement in square-wave voltammograms recorded for solid samples containing a reference compound R, upon additions of a A- (or B-) containing standard compound. The method allows to the determination of the mass fraction of A and B by applying the H-point standard addition method to solid state voltammetry. The quotients between the currents measured at two selected potentials and the peak current of R vary linearly with the mass ratio of the added standard…

Analysis of microsphere oblique impact with planar surfaces based on the independent friction-restitution approach

The independent friction restitution closure (IFR) previously applied to describe planar oblique impact of a homogeneous sphere on an infinitely massive rough plane is applied here to microsphere collisions and is extended to describe horizontal launch experiments. The model provides analytical solutions of the motion equations based on a unique set of values of the coefficients of normal and tangential restitution and friction. Comparison with experimental data in literature for the impact of microspheres of diameter <100 mu m yields a satisfactory agreement between experimentation and theory.

Insights of Tris(2-pyridylmethyl)amine as anti-tumor agent for osteosarcoma: experimental and in silico studies

Abstract Osteosarcoma (OS) is a malignant bone tumor and its occurrence is associated with high levels of microRNAs (miRNAs) and critical protein sinvolved on intracellular signaling pathways. Cisplatin and Doxorubicin are employed on chemotherapy, but their use cause side effects and contributes to multidrug resistance. Since several tripodal amines have been studied as anticancer agents, tris(2-pyridylmethyl)amine (TPA) was investigated against osteosarcoma cells. Here we show that TPA exhibits activity against MG-63 and Saos-2 cells. Cyclic voltammetry results indicate an interaction between TPA and dsDNA, denoted by blocking of the proton-assisted reduction of the 2-pyridylmethyl moiety…

Enhanced catalytic electrochemical reduction of dissolved oxygen with ultracleancucurbituril[7]-capped gold nanoparticles

Gold nanoparticles capped with cucurbituril[7] have been prepared in the absence of metallic cations and organic ligands. Remarkably, these nanohybrids encapsulate dissolved oxygen and are highly active in electrochemical reduction. The effect of the presence of sodium and ammonium salts on this catalysed process is also analysed.

A step forward in the development of superoxide dismutase mimetic nanozymes: the effect of the charge of the surface on antioxidant activity

Two binucleating hezaaza macrocycles containing a pyridinol spacer have been prepared and characterised. Protonation studies indicate the deprotonation of the phenol group at relatively low pH values with the concomitant occurrence of a keto-enolic equilibrium. These ligands readily form binuclear Cu2+ and Zn2+ complexes as denoted by potentiometric and spectroscopic studies. The binding of the metals yields to the ready deprotonation of the phenol with the stabilisation of the keto form that results in complexes of greater stabilities than the analogous ones containing pyridine as spacer instead of pyridine. Mixed Cu2+–Zn2+-complexes were also detected in aqueous solutions containing equim…

Electrochemical Characterization and Dating of Archaeological Leaded Bronze Objects Using the Voltammetry of Immobilized Particles

Financial support from the MINECO Projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P, which are supported by ERDF funds, is gratefully acknowledged. We wish to thank the Fondo de Arte y Patrimonio of the Universitat Politecnica de Valencia; the Museu de Prehistoria of Valencia, and its director Helena Bonet and curator Jaime Vives-Ferrandiz; and the Museu Municipal of Xativa and its director Angel Velasco. We also wish to thank Dr Jose Luis Moya Lopez and Mr Manuel Planes Insausti (Microscopy Service of the Universitat Politecnica de Valencia) for technical support.

Electrochemical Characterization of Corrosion Products in Leaded Bronze Sculptures Considering Ohmic Drop Effects on Tafel Analysis

[EN] The characterization of corrosion products in leaded bronze based on the voltammetry of immobilized particles methodology is described. Voltammetric data, supported by Fourier transform infra-red spectroscopy, field emission scanning electron microscopy-energy dispersive X-ray microanalysis (FESEM-EDX) and scanning electrochemical microscopy (SECM) allow the identification of copper and lead corrosion materials. The mutual influence of such products is modeled upon considering uncompensated ohmic drops in the Tafel analysis of the rising portion of the respective voltammetric signals for their electrochemical reduction.

Cover Picture: Electrochemical Characterization of Coinage Techniques the 17th Century: The maravedís Case (Electroanalysis 9/2017)

Electrochemical ecology: VIMP monitoring of plant defense against external stressors

The use of the voltammetry of immobilized particles (VIMP) approach, by means of the voltammetric response of microparticulate films from ethanolic leaf extracts in contact with aqueous electrolytes and direct contact probe leaf voltammetry, to monitor the defense of plants against external stressors is described. This approach is applied to study the chemical communication between plants of Peperomia obtusifolia A. Dietr. submitted to herbivory by the beetle Monoplatus sp.

Screening and mapping of pigments in paintings using scanning electrochemical microscopy (SECM)

The use of the scanning electrochemical microscopy (SECM) technique for identifying and mapping of both organic and inorganic pigments in sub-microsamples from pictorial specimens is described. This methodology, inspired by the voltammetry of immobilized particles technique, permits the study of textural properties of paint layers and mapping the distribution of pigment grains upon application of different potentials to the substrate. A combination of the redox competition SECM strategy with voltammetry yields a local identification methodology for different organic and inorganic pigments in paint samples.

"One-touch" voltammetry of microparticles for the identification of corrosion products in archaeological lead

Voltammetry of microparticles is applied to the identification of lead corrosion products by means of an essentially non-invasive 'one-touch' technique based on the use of graphite pencil. This methodology permits the mechanical attachment of few nanograms of sample from the surface of lead archaeological artefacts to a paraffin-impregnated graphite electrode, which, upon immersion in aqueous electrolytes, provides distinctive voltammetric responses for litharge and cotunnite- anglesite-, cerusite-based corrosion products. The reported method is applied to the identification of corrosion products in archaeological lead pieces from different Iberian sites in Valencia (Spain). © 2011 WILEY-VC…

Bisferrocenyl-functionalized pseudopeptides: access to separated ionic and electronic contributions for electrochemical anion sensing

Pseudopeptidic receptors containing ferrocene fragments have been prepared and their response to a series of anions was measured by a voltammetry of microparticles methodology. Such water-insoluble compounds yield anion-assisted reversible solid-state oxidations differing in their open-circuit potential and their midpeak potential recorded in cyclic voltammetric measurements. The difference between those potentials provides the individual thermodynamic contributions of electron and proton transfer, revealing that the mechanism of an ion-sensitive electrode can differ in potentiometry and voltammetry. The studied receptors are potentially interesting for potentiometric sensing, showing relat…

Experimental and theoretical study of possible correlation between the electrochemistry of canthin-6-one and the anti-proliferative activity against human cancer stem cells

Abstract This work presents an approach to study the performance of novel targets able to overcome cancer stem cell chemoresistance, based on the voltammetric data for microparticulate films of natural or synthetic alkaloids from the canthin-6-one series. A comparison of this voltammetric technique with conventional solution phase electrochemistry suggests the differences in the anti-proliferative activity of canthin-6-ones could be tentatively correlated to their different capacity to generate semiquinone radical anions. These data also match theoretical calculations.

Characterization of traditional artificial patinas on copper using the voltammetry of immobilized particles

[EN] The voltammetry of immobilized particles methodology (VIMP) is used to characterize the composition of artificial patinas on copper. The voltammetric response of carbonate-, nitrate-, chloride-, sulfate-, and sulfide-based patinas is described using sub-microsamples attached to graphite electrodes in contact with aqueous acetate buffer. Patina-characteristic voltammetric profiles are obtained for the different artificial patinas that can be recognized using the generalized Tafel analysis of the voltammetric curves. VIMP data could also provide layer-by-layer information about composition and compactness/crystallinity of the patinas for which a simplified theoretical modeling is present…

Electrochemical characterization of cobalt cordierites attached to paraffin-impregnated graphite electrodes

The electrochemistry of α, β and μ cobalt-containing cordierites (Co2Al4Si5O18) attached to paraffin-impregnated graphite electrodes has been studied by linear scan and cyclic voltammetries in HCl+NaCl and NaOH electrolytes. This electrochemistry is compared with that of vitreous cobalt cordierite, cobalt(II) oxide and cobalt spinel aluminate (CoAl2O4), the two last taken as reference materials. Electrochemical processes involve the site-characteristic reduction of Co(II) species to cobalt metal near to −0.5 V vs. SCE and their oxidative dissolution near +0.3 V, accompanied by solid state interconversion between Co(II) and Co(III) at potentials above +0.45 V. Cordierite-modified electrodes …

Dating archeological lead artifacts from measurement of the corrosion content using the voltammetry of microparticles.

A methodology for dating archeological lead artifacts based on the voltammetry of microparticles is described. This methodology is based on the comparison of the height of speci¿c voltammetric features from PbO2 and PbO corrosion products formed under long-term alteration conditions. Calibration of the method was performed with the help of a series of well-documented lead pieces from the funds of di¿erent museums of the Comunitat Valenciana (Spain) covering from the ¿fth century B.C. to present day. The variation of peak currents with the time of corrosion can be¿tted to the same potential rate law as that found by Reich (R = 0.070 ( 0.005), using measurements on the Meissner fraction in th…

Application of the Generalized Molar-Ratio Method to the Determination of the Stoichiometry and Apparent Binding Constant of Nanoparticle-Organic Capping Systems

A generalization of the molar-ratio method is applied to the determination of the stoichiometry and apparent binding constant of metal nanoparticle-organic capping complexes (MmLx) using voltammetric data for the oxygen reduction reaction (ORR) in air-saturated aqueous phosphate buffer solutions. The method is applied to the formation of binary nanohybrids consisting of gold nanoparticles (AuNPs) capped with a rigid spacer, cucurbit[7]uril (CB), termed AuNP@CB, as well as to the formation of their ternary complexes (MmLxBz) with methylene blue (MB), termed AuNP@CB@MB. The obtained stoichiometries correspond to binding of four Au surface atoms for each CB unit.

Bone-Targeted Cisplatin-Complexed Poly(γ-benzyl-L-glutamate)-Poly(glutamic acid) Block Polymer Nanoparticles: An Electrochemical Approach

The voltammetric response of different osteotropic multifunctional nanoparticles based on cisplatin-complexed poly(γ-benzyl-L-glutamate)–poly(glutamic acid) block polymer (CDDP-PBLG-b-PGlu) copolymer, with or without poly(γ-benzyl-L-glutamate)–poly(ethylene glycol) block polymer (PBLG-b-PEG), and having bone-targeting properties is studied at biologically relevant pH. Significant differences in the cisplatin-centered voltammetric signals allow monitoring of the association of cisplatin to nanoparticles as well as release kinetics from them, in agreement with atomic absorption spectroscopy data. Electrochemical studies reveal that the cisplatin association is significant only if the proporti…

Voltammetric Identification of Lead(II) and (IV) in Mediaeval Glazes in Abrasion-Modified Carbon Paste and Polymer Film Electrodes. Application to the Study of Alterations in Archaeological Ceramic

Direct identification of lead(II) and (IV) in glazed ceramics by cyclic voltammetry and differential pulse voltammetry is described. Characteristic cathodic and anodic profiles are obtained for microsample coatings in Paraloid B72-film electrodes immersed in NaCl and HAc/NaAc media. The electrochemical response of PbO, PbO2 and Pb3O4, and a series of test specimens of glaze is compared with that of microsamples extracted from the glaze of blue and white decorated ceramic produced in Manises (Spain) in the 15th century which have been buried in a damp place. Under abrasive conditions, striping peaks at –0.12 and –0.25 V (vs. SCE) appear for Pb(IV) centers and, at –0.55 and –0.75 V, for Pb(II…

Self-assembly of catalytically-active supramolecular coordination compounds within metal-organic frameworks

[EN] Supramolecular coordination compounds (SCCs) represent the power of coordination chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesized in solution, with isolated fully coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-organic frameworks (MOFs) show unique features to act as chemical nanoreactors for the in situ synthesis and stabilization of otherwise not accessible functional species. Here, we present the self-assembly of Pd-II SCCs within the confined space of a pre-formed MOF (SCCs@MOF) and its post-assembly metalation to give a Pd-II-Au-III supra molecular assembly, c…

Isomerization and redox tuning in ‘Maya yellow’ hybrids from flavonoid dyes plus palygorskite and kaolinite clays

Abstract The composition of the organic fraction of organic–inorganic hybrid materials prepared upon attachment of different natural, ‘historical’ flavonoid yellow dyes (zacatlaxcalli, fustic, marigold and cosmos) to palygorskite and kaolinite clays is described. Upon thermal treatment between 100 and 180 °C, significant isomerization and oxidation reactions occur thus resulting in the formation of polyfunctional materials potentially usable for therapeutic, catalytic and art purposes. The dye attachment to the clays would define a ‘Maya chemistry’ whose complexity could explain the versatile use of such materials in the pre-Columbian cultures.

Multiple-scan voltammetry and OCP: Archaeometric tools for dating archaeological bronzes

[EN] The application of a multiple-scan strategy to nanosamples taken from 18 cross-sections of Bronze Age arms and armour, as well as two Roman coins using two solid-state electrochemical techniques, the voltammetry of immobilized microparticles (VIMP) and open circuit potential measurements (OCP) is described. The voltammetric responses in contact with aqueous acetate buffer can be attributed to the reduction of cuprite with variable degree of compaction and crystallinity revealing significant differences in the gradient of such properties with depth. Such differences are also revealed by "dry" OCP measurements connecting points in the cross section near and separated from the corrosion l…

Electrochemical Analysis of Catalytic and Oxygen Interfacial Transfer Effects on MnO2 Deposited on Gold Electrodes

[EN] A theoretical model for obtaining thermochemical and kinetic information on oxygen interfacial transfer in metal oxides deposited on gold electrodes, based in the voltammetry of immobilized particle methodology, is presented. It is applied to MnO2 microparticulate deposits on gold in contact with aqueous NaOH solution using the voltammetric signals for the oxidation of gold to gold oxide monolayer and its subsequent desorptive reduction. Assuming reversibility, voltammetric peak potentials permit to estimate a variation of Gibbs free energy of interfacial oxygen transfer of -32 +/- 3 kj mol(-1). Analysis of peak current data based on the Sharp-Hancock formalism of solid-state kinetics …

Electrochemical tomato (Solanum lycopersicum L.) characterisation using contact probe in situ voltammetr

[EN] An in situ electrochemical contact probe methodology for characterising tomato samples is proposed. It is based on the record of the voltammetric response of antioxidant compounds when glassy carbon electrodes are inserted into the pericarp of fresh tomato specimens cut in half. The absence of pretreatment and in situ sampling avoid sample contamination and the oxidation of air-sensitive compounds thus increasing the representativity of the analytical data relative to conventional electrochemical analysis. Characteristic voltammetric responses recorded for such compounds, including rutin, chlorogenic acid, naringenin, naringenin chalcone and ascorbic acid have been obtained. A positive…

Electrochemistry in Archaeology and Art Conservation

Electrochemistry of iron oxide pigments (earths) from pictorial microsamples attached to graphite–polyester composite electrodes

The electrochemical response of different iron pigments attached to graphite–polyester composite electrodes is described. Characteristic differential pulse voltammetric profiles were obtained for green earth, iron oxide red, Mars black, ochre yellow, Sienna raw, umber raw and Van Dyke brown. Proton-assisted reductive dissolution processes occur at the three-phase boundary of the substrate electrode–attached solid–electrolyte solution system. Microsamples extracted from polychromed sculptures, canvas paintings, wall paintings, altarpieces and panel paintings from Spain, Ethiopia and Italy from the 12th to the 20th centuries were electrochemically identified in agreement with polarized light …

Electrochemistry-based chemotaxonomy in plants using the voltammetry of microparticles methodology

A methodology for characterizing vegetal taxonomic groups using microextraction-assisted voltammetry of microparticles is described. It is based on recording the voltammetric response of microparticulate films of polyphenolic compounds of leaf extracts using different organic solvents. As a result, characteristic voltammetric profiles, tentatively defining an electrochemolomic response, are obtained. Bivariant and multivariant chemometric evaluation of the voltammetric responses of such films allows characterizing vegetal families. Analysis of voltammetric responses for a set of species of the Rosales order suggests that electrochemical data can be correlated with phylogenetic trees.

Hyperbolic subtraction method: Determination of the concentration of an analyte in the presence of an unknown interferent via spectral data.

A theoretical model to determine the concentration of an analyte in the presence of unknown interferents using spectral-type data is described. The method involves absorbance measurements at three wavelengths and the calculation of specific absorbances yielding a hyperbolic relationship between absorbance ratios and analyte concentrations. The concentration of the analyte of known spectrum can be determined in the presence of an interferent or mixture of interferents of unknown concentration(s) and spectra can be determined combining data for different sets of wavelengths. Application to indigo and isatin solutions in DMSO related to the so-called Maya blue problem is reported as an illustr…

A testimony of pitch production in the Protohistory of the Iberian Peninsula: The kiln of La Illeta dels Banyets (El Campello, Alicante)

Durante la campaña de 2009-2010 en el yacimiento arqueológico de la Illeta dels Banyets se localizó un basamento circular, una pileta y un depósito excavado en el subsuelo que formaban parte de un único equipamiento dedicado a una actividad productiva. Por sus características y por los análisis antracológico y químico se ha identificado como un horno para la destilación de pez o brea, cuyo proceso de fabricación se ha visto confirmado con paralelos arqueológicos y etnográficos. Datado entre finales del siglo IV y la primera mitad del siglo III a.C., es la primera instalación completa de este tipo conocida para el periodo protohistórico en la península ibérica. During the 2009-2010 campaign …

Electrochemical identification of flavonoid dyes in solid work of art samples by abrasive voltammetry at paraffin-impregnated graphite electrodes.

Abstract An electrochemical method for identifying flavonoid-type dyes in microsamples from works of art is reported. Square wave voltammograms of natural insoluble dyestuffs based on flavonoid structure dragoon's blood, weld, old fustic, gamboge, Brazilwood and logwood (Campeche wood) attached to paraffin-impregnated graphite electrodes in contact with 0.25 M HAc + 0.25 M NaAc aqueous buffer display characteristic peaks in the potential region between +0.85 and −0.85 V versus AgCl/Ag. Sequential experiments in contact with 0.05 M AlCl 3 and 0.05 M Na 2 MoO 4 plus HAc/NaAc and 0.05 M H 3 BO 3  + 0.10 M NaOH solutions also provide dye-characteristic signals allowing for an unambiguous identi…

Analytical study of canvas painting collection from the Basilica de la Virgen de los Desamparados using SEM/EDX, FT-IR, GC and electrochemical techniques

A new method, based on the combined use of scanning electron microscopy-x-ray microanalysis, Fourier transform infrared spectroscopy, gas chromatography and differential pulse voltammetry, is proposed which permits a parallel investigation of organic and inorganic materials and the characterization of the artistic technique employed in canvas painting. The proposed method has led to analyze succesfully the canvas painting collection exhibited in the Basílica de la Virgen de los Desamparados (Valencia, Spain) which includes art works from 17th to 20th century.

Thermal decomposition of chromite spinel with chlorite admixture

Abstract The behaviour of minerals in a South African chromite ore during the increasing of the temperature has been studied. Firstly, the changes produced during the ignition process have been examined by means of thermal and differential analysis (TGA–DTA) until 1200 °C. The characterization of the initial mineral and those obtained after heating at several temperatures in room atmosphere has been performed by X-ray diffraction (XRD). Moreover, voltammetric analyses have allowed to determine the variation of the iron oxidation degree in the studied materials. Light microscopy was applied to find more information about the different phases by their colour. During the heating, a wide range …

Solid-State Electrochemical Method for Determining Core and Shell Size in Pd@PdO Nanoparticles

Electrochemical characterization of palladium nanoparticles surrounded by a palladium oxide shell (Pd@PdO) is described from a combination of voltammetry plus electrochemical quartz crystal microbalance experiments at nanoparticle deposits on graphite electrodes in contact with aqueous H2SO4 and NaOH solutions. A method for determining the metal core size and oxide shell thickness of the Pd@PdO nanoparticles, based on a combination of conventional voltammetry of nanoparticles in DMSO solution and voltammetry of nanoparticle deposits in contact with 0.10 M aqueous NaOH solution, is described.

Screening of Iberian Coinage in the 2(th)-1(th) BCE Period Using the Voltammetry of Immobilized Particles

[EN] The voltammetry of immobilized particles (VIMP) was applied for grouping a series of 86 Iberian coins nominally minted in the cities of Iltirta, Castulo and Obulco in the 2(th)-1(th) BCE period for which there are no chronological data. Using characteristic signatures for the reduction of cuprite, tenorite and lead corrosion products in the patina of the coins, voltammetric grouping of coins was proposed. Voltammetric data were found to be consistent with textural and compositional properties of the surface and subsurface of selected coins using FIB-FESEM-EDX. The obtained data confirmed a clear separation between the productions of Iltirta on one side, and those of Castulo and Obulco …

ELECTROCHEMISTRY AND AUTHENTICATION OF ARCHAEOLOGICAL LEAD USING VOLTAMMETRY OF MICROPARTICLES: APPLICATION TO THE TOSSAL DE SANT MIQUEL IBERIAN PLATE

The authors wish to thank the Museu de Prehistoria de Valencia, Museu Arqueologic de Borriana and Museu Municipal de Montcada for the access to their archives and funds. Financial support is gratefully acknowledged from the Spanish 'I+D+I MICINN' project CTQ2008-06727-C03-01 and 02/BQU, supported by ERDEF funds. The authors wish to thank Mr Manuel Planes i Insausti and Dr Jose Luis Moya Lopez, the technical supervisors responsible for the UPV Electron Microscopy Service.

Screening and authentication of herbal formulations based on microextraction-assisted voltammetry of microparticles

A simple solid state electrochemical methodology for screening and authentication of herbal formulations is described. The proposed method is based on the recording of the voltammetric response, in contact with aqueous buffers, of microparticulate films of antioxidant compounds resulting from micro-extraction of dried herbal samples with ethanol or acetone. The obtained voltammetric responses led us to differentiate between diverse active components upon application of bivariate and multivariate chemometric techniques. Resolution of herbal preparations containing two or more components is possible when well-separated voltammetric signals are recorded. In favorable cases, such characteristic…

Discrimination and provenances of Phoenician red slip ware using both the solid state electrochemistry and petrographic analyses

[EN] Solid state electrochemistry based on the voltammetry of immobilized microparticles (VIMP) methodology is applied to a series of 80 Phoenician Red Slip samples from the archaeological sites of Motya (Sicily, Italy), Mogador (Morocco), Ramat-Rahel (Israel), Sulky (Sardinia, Italy), Tas Silg (Malta), Pantelleria (Italy), and Cadiz (Spain), dated from the 8(th) to the 6(th) century BC. Upon attachment of sub-microsamples to graphite electrodes in contact with aqueous H2SO4 electrolyte, voltammetric features due to the reduction of Fe(III) minerals and the oxidation of Fe(II) ones, complemented with electrocatalytic effects on oxygen reduction and oxygen evolution reactions, provide charac…

Identification of inorganic pigments from paintings and polychromed sculptures immobilized into polymer film electrodes by stripping differential pulse voltammetry

Abstract Inorganic pigments in paintings and polychromed sculptures are studied by cyclic voltammetry and differential pulse stripping voltammetry using micro-sample coatings in Paraloid B72-film modified electrodes. Characteristic cathodic and anodic differential pulse profiles were obtained in the +0.4 to −1.0 V vs. SCE potential range for different cadmium, copper, lead, mercury and zinc pigments used in traditional colour palettes. Under optimized conditions, excellent reproducibility was obtained. Microsamples extracted from polychromed sculptures, wall paintings, canvas paintings, panel paintings and altarpieces from Spain, Ethiopia and Italy from the 12th to the 20th centuries have b…

Hematite as an Electrocatalytic Marker for the Study of Archaeological Ceramic Clay bodies: A VIMP and SECM Study**

[EN] The electrocatalytic effect exerted by hematite, a ubiquitous component of clay bodies, on the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can be used to acquire information on archaeological ceramics. The solid-state voltammetric response of different hematite and ochre specimens, accompanied by SECM analysis in contact with 0.10 M HCl aqueous solution, is described. In air-saturated solutions, catalytic effects on the ORR and OER are accompanied by Fe(III)/Fe(II) and Fe(IV)/Fe(III) redox reactions. Such processes are conditioned by a variety of factors, the hydroxylation degree of the mineral surfaces being particularly influential, and exhibit significant var…

Determination of the Boron/Lead Ratio in Ceramic Materials Based on Electrochemical Quartz Crystal Microbalance

A method for quantitatively determining the relationship boron/lead in ceramic materials is presented. It is based on the attachment of microsamples of ceramic frits to an electrochemical quartz crystal microbalance (EQCM). After a reductive deposition step in the � 0.25 to � 0.85 V (vs. AgCl/Ag) potential range, well-defined stripping peaks are recorded in 0.10 M NaCl plus 0.10 M mannitol. The deposition of boron and lead from suspensions of solid materials, and its subsequent oxidative dissolution can be monitorized at the EQCM. The quotient between the maximum mass gain and the corresponding charge passed enables for a direct quantitation of the boron/lead molar ratio in ceramic material…

The evolution of COVID-19: A discontinuous approach.

The evolution of the COVID-19 disease is monitored on the basis of the daily number of infected patients and the daily number of deaths provided from national health agencies. The variation of such parameters with time parallels that described for the growth/decay of historic transportation systems revealing the appearance of discontinuities. The evolution of the pandemic disease is represented in terms of two nominally equivalent formulations: a logistic model with sharp changes in its rate parameters, and in topological terms resulting in 2nd order phase transitions in the infected patients/time space.

‘Dry’ electrochemistry: A non-invasive approach to the characterization of archaeological iron objects

A methodology for monitoring the corrosion state of archaeological iron objects using ‘dry’ open circuit potential (OCP) measurements is described. Application of this technique to a set of objects from La Bastida de les Alcusses archaeological site (Moixent, València, Spain), dating back to the 4th century BCE, reveals significant differences depending on the conservation state. The transient OCP responses (which last between a few seconds and 10–15 min) were superimposed with much shorter (less than one second) intense features. Fil: Doménech Carbó, Antonio. Universidad de Valencia; España Fil: Peiró Ronda, María Amparo. Museu de Prehistòria de València; España Fil: Vives Ferrándiz, Jaime…

Dating archaeological strata in the Magna Mater temple using solid-state voltammetric analysis of leaded bronze coins

[EN] The application of solid state electrochemistry techniques for dating archaeological strata using lead-containing bronze coins is described. The proposed methodology was applied to samples coming from the Roman archaeological site of Magna Mater Temple (Rome, Italy) occurring in different strata dating back between the second half and the end of the 4(th) century A.D. and the 20(th) century. The voltammetric signatures of copper and lead corrosion products in contact with aqueous acetate buffer, as well as the catalytic effects produced on the hydrogen evolution reaction, were used for establishing the age of different strata and dating coins belonging to unknown age. Voltammetric data…

Tunability by alkali metal cations of photoinduced charge separation in azacrown functionalized graphene.

A modified graphene oxide containing aza-9-crown-3 ether units covalently anchored has been prepared; aqueous suspensions of this material in the presence of Li(+), Na(+) and K(+) cations exhibit enhanced electrochemical response, enhanced photoinduced charge separation and longer lifetimes, facts that can be attributed to stabilization of electrons on graphene oxide by the nearby alkali metal cation-azacrown complexes.

Contact probe voltammetry for in situ monitoring of the reactivity of phenolic tomato (Solanum lycopersicum L.) compounds with ROS

The application of an in situ electrochemical contact probe methodology for monitoring reactivity of antioxidant polyphenolic compounds in tomato fruits is described. Upon electrochemical generation of reactive oxygen species (ROS), characteristic voltammetric responses were recorded for compounds resulting from the reaction of such species with tomato compounds. This suggests that new electrochemically oxidizable compounds are generated from the oxidation of highly reactive polyphenolic compounds with ROS. Therefore, an evaluation of the antioxidant capacity of such species could be made from voltammetric data for different tomato varieties.

Independent friction-restitution approach to analyze anomalies in normal kinematic restitution in oblique impact

Abstract Oblique impact between rigid bodies is usually described in terms of the coefficients of normal and tangential restitution. When the contact between bodies occurs under elasto-plastic conditions, the normal coefficient of restitution can be ordinarily taken as essentially constant. Several anomalous results reported by Louge and Adams (Anomalous behavior of normal kinematic restitution in the oblique impacts of a hard sphere on an elasto-plastic plate. Phys. Rev. E 65 (2002) 021303), however denoted a significant variation of this coefficient with the incidence angle under certain conditions. This anomalous behavior is interpreted here within the independent friction and restitutio…

Synthesis, Characterization of FexZr1-xO2Solid Solution Nanoparticles and Bulk Powders Prepared Using a Sol-Gel Technique

Electrochemical Characterization of Archaeological Tin-Opacified Lead-Alkali Glazes and Their Corrosion Processes

The electrochemical response of weathered and unweathered archaeological tin-opacified glazes attached to paraffin-impregnated graphite electrodes is described. Upon comparison with the square wave voltammetric response of SnO2, PbO and PbO2, Sn- and Pb-centered reduction processes can be characterized. Reduction of Sn(IV) involves the stepwise formation of solid Sn(II) and Sn metal, successively, at potentials of −0.08 and −0.55 V vs. AgCl/Ag. Reduction of network-modifier Pb(II) in glazes occurs at −0.5 V and is accompanied by the reduction of network-forming Pb(IV) at potentials ranging from +0.65 to +0.20 V, confirming the presence of such centers in glazes. Voltammetric data suggest th…

Composition and Color of Maya Blue: Reexamination of Literature Data Based On the Dehydroindigo Model

[EN] An analysis of literature data studying the composition and color of Maya blue (MB) type materials prepared from indigo, dehydroindigo, and different aluminosilicates, accompanied by new spectral data, is presented. After thermal treatment at above 100 degrees C, indigo-based specimens displayed Raman and UV-vis spectroscopic features common to those of equivalent dehydroindigo-based replicants, thus supporting the socalled dehydroindigo model (J. Phys. Chem. B 2006, 110, 6027-6039) in which the dehydroindigo/indigo ratio, increasing with temperature, is crucial to determine the color of MB and its variability. The current analysis supports the view of MB as a polyfunctional hybrid mat…

Validation of a method for the determination of boron in ceramic materials by X-ray fluorescence spectrometry

Abstract A method is proposed for boron determination in ceramic materials, boracic raw materials and ceramics frits of different compositions by wavelength dispersive X-ray fluorescence technique. The instrumental conditions were studied and the sample preparation procedures were optimized. The reference method used was the potentiometric titration of mannitol–boric complex acid and the technique was optimized for the determination of B 2 O 3 in each of the materials used. The samples for XRF determination were obtained as pellets and as glass discs. For the pellets different binders were studied, such as mannitol and cellullose for the samples of raw materials, and polyvinylpirrolidone an…

Electrochemical discrimination of manufacturing types of pottery from Magna Mater Temple and Fora of Nerva and Caesar (Rome, Italy)

Abstract The voltammetry of immobilized microparticles (VIMP) methodology is applied to a series of pottery samples from the Roman sites of Nerva's Forum (second half of 9th-early 11th A.D), Caesar's Forum (second half of 9th-early 11th A.D) and Magna Mater Temple (III century). The VIMP sampling applied to voltammetric and electrochemical impedance spectroscopy (EIS) measurements was applied by the first time to acquire archaeometric information on archaeological pottery. VIMP measurements using pressed sample pellets on gold electrodes in contact with air-saturated 0.10 M H2SO4 have permitted to detect voltammetric signals for the reduction/oxidation of Fe and Mn minerals as well as catal…

Nanolayered Cobalt-Molybdenum Sulfides as Highly Chemo- and Regioselective Catalysts for the Hydrogenation of Quinoline Derivatives

[EN] Herein, a general protocol for the preparation of a broad range of valuable N-heterocyclic products by hydrogenation of quinolines and related N-heteroarenes is described. Interestingly, the catalytic hydrogenation of the N-heteroarene ring is chemoselectively performed when other facile reducible functional groups, including alkenes, ketones, cyanides, carboxylic acids, esters, and amides, are present. The key to successful catalysis relies on the use of a nanolayered cobalt-molybdenum sulfide catalyst hydrothermally synthesized from earth-abundant metal precursors. This heterogeneous system displays a tunable composition of phases that allows for catalyst regeneration. Its catalytic …

Identification of Manganese(IV) Centers in Archaeological Glass Using Microsample Coatings Attached to PolymerFilm Electrodes

Identification of MnO2 nodulae in archaeological glass by linear scan and differential pulse voltammetry using abrasive-conditioned microsamples attached to polymer film (Elvacite 2044) electrodes is described. Voltammetric responses for manganese-containing samples parallels to those obtained for β- and γ-MnO2 upon immersion of modified electrodes into NaCl, KCl and acetic/acetate aqueous media. The observed electrochemical response provides information on the open microporous structure of the MnO2 forms and the conditions of their formation during the weathering process of buried glass.

Electrochemical determination of boron in minerals and ceramic materials

Abstract A method for quantitatively determining boron in minerals and ceramic materials is described. It is based on the abrasive attachment of mixtures of ZnO plus sample to PIGEs. After a reductive deposition step, square wave voltammograms recorded for those modified electrodes immersed into 0.10 M NaCl+0.25 M mannitol provide well-defined stripping peaks at −0.85 and −0.15 V vs. AgCl/Ag for the oxidation of Zn and B, respectively. The quotients between the peak areas and the peak currents for the stripping oxidation of B and Zn vary linearly with the molar ratio of B and Zn in the mixture, thus providing an electrochemical method for determining the boron content in solid samples. Resu…

Insight into the Mechanism of Action of Marine Cytotoxic Thiazinoquinones

The electrochemical response of four natural cytotoxic thiazinoquinones isolated from the Aplidium species was studied using conventional solution-phase and solid-state techniques, based on the voltammetry of immobilized particles methodology. The interaction with O-2 and electrochemically generated reactive oxygen species (ROS) was electrochemically monitored. At the same time, a molecular modeling study including density functional theory (DFT) calculations was performed in order to analyze the conformational and electronic properties of the natural thiazinoquinones, as well as those of their reduced intermediates. The obtained electrochemical and computational results were analyzed and c…

Screening and authentication of tea varieties based on microextraction-assisted voltammetry of microparticles

Abstract A simple electrochemical methodology for screening and authentication of green, black and red tea varieties is proposed. It is based on the record of the voltammetric response of microparticulate films of antioxidant compounds resulting from an ethanolic micro-extraction of commercial tea herbal preparations in contact with aqueous buffers. The obtained voltammetric responses led us to differentiate between diverse tea varieties upon application of bivariant and multivariant chemometric techniques, including discrimination of mixtures of teas with sensitivity estimated of 5.0 μA mg −1 with a detection limit of 0.01 mg of tea sample. Under the proposed conditions 100% discrimination…

Voltammetric analysis of iron oxide pigments

Eighteen earthy and four pure synthetic pigments containing alpha-Fe2O3 (hematite), alpha-FeOOH (goethite) and poorly crystalline Fe and Mn oxide species were analyzed by voltammetry of microparticles. Three natural samples were subjected to an interlaboratory test to evaluate the reproducibility of the voltammetric peak potentials and peak shapes. The results confirmed that linear-sweep voltammetry is able to distinguish between poorly crystalline, ferrihydrite-like oxides and well-crystalline hematite and goethite and to detect XRD-amorphous Mn(III,IV) oxides via the peak occurrence. Voltammetry is further able to distinguish between pigments containing well-crystalline goethite (accordin…

Electrochemical identification of painters/workshops: The case of Valencian Renaissance-Baroque painters (ca. 1550- ca. 1670)

[EN] The voltammetry of immobilized particles (VIMP) methodology was applied to discriminate the oil painting production of a series of seven painters/workshops that worked in Valencia (Spain) between ca. 1530 and ca. 1650. When submicrosamples used for cross-section FESEM/EDX analysis were attached to graphite electrodes in contact with aqueous acetate buffer, well-defined responses were obtained. The reductive processes of lead pigments (lead white and lead-tin yellow) overlapped those associated to the lead soaps and other species resulting from the pigment-oil binder interaction in the sample. Such responses, which are theoretically modeled, were sensitive to changes in paint type and d…

Electrochemical monitoring of ROS generation by anticancer agents: the case of chartreusin

Solution phase and solid-sate electrochemical techniques centered in the voltammetry of microparticles approach are applied for testing the cytotoxic activity of anticancer drugs. The possibility of electrochemical generation of reactive oxygen species (ROS) is exploited for evaluating their contribution to cellular damage. The described methodology is applied to the case of chartreusin (Ch) whose electrochemistry in non-aqueous solutions and in the solid state in contact with aqueous electrolytes is described in the absence (experimental data were confirmed by theoretical calculations) and in the presence of double-stranded DNA (dsDNA). In parallel, scanning electrochemical microscopy (SEC…

Electrochemical dating of archaeological gold based on refined peak current determinations and Tafel analysis

Abstract This report proposes a refined method to date archaeological gold samples based on the Tafel analysis of the ascending part of voltammetric curves corresponding to the oxidation of surface flakes of gold in contact with hydrochloric acid aqueous electrolyte. This allows estimating the equilibrium potential of gold oxidation correcting for irreversibility effects. This equilibrium potential can be correlated with the coverage of adsorbed oxygen species and hence the estimated age of the gold samples. A satisfactory potential/time calibration graph was constructed from a set of archaeological samples including two sets of samples from the Mapungubwe Gold Collection, South Africa (120…

Electrochemical characterization of solid state reaction kinetics using voltammetry of microparticles. Application to thermal decomposition of iron chromites

The voltammetry of microparticles is applied to characterize the electrocatalytic ability of solids towards selected electrochemical processes. The variation of catalytic currents under fixed electrochemical conditions permits to obtain composition/time data to be fitted with solid state kinetic models. This methodology is applied to analyze the thermal decomposition of magnesiochromite ferroan and chlorite chromian standards and a South Africa iron chromite ore on the basis of the significant catalytic effect on the electrochemical oxygen evolution reaction (OER) in aqueous alkaline media at mineral-modified graphite electrodes. Measurement of the time variation of catalytic current for OE…

Analyzing chemical changes in verdigris pictorial specimens upon bacteria and fungi biodeterioration using voltammetry of microparticles

[EN] It is reported the application of the voltammetry of microparticles (VMP), complemented with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and field emission scanning electron microscopy (FESEM) techniques, to monitor the deterioration of verdigris pictorial specimens under the action of different biological agents. This methodology would be of application for identifying the type of biological agent causing deterioration of paintings, which is an important problem affecting cultural heritage. The analysis of biodeterioration processes is complicated by the fact that the action of microorganisms can affect both pigment and binding media. The deteriorat…

Synthesis, Characterization, and Cu(2+) Coordination Studies of a 3-Hydroxy-4-pyridinone Aza Scorpiand Derivative.

The synthesis, acid-base behavior, and Cu(2+) coordination chemistry of a new ligand (L1) consisting of an azamacrocyclic core appended with a lateral chain containing a 3-hydroxy-2-methyl-4(1H)-pyridinone group have been studied by potentiometry, cyclic voltammetry, and NMR and UV-vis spectroscopy. UV-vis and NMR studies showed that phenolate group was protonated at the highest pH values [log K = 9.72(1)]. Potentiometric studies point out the formation of Cu(2+) complexes of 1:2, 2:2, 4:3, 1:1, and 2:1 Cu(2+)/L1 stoichiometries. UV-vis analysis and electrochemical studies evidence the implication of the pyridinone moieties in the metal coordination of the 1:2 Cu(2+)/L1 complexes. L1 shows …

Voltammetry of microparticles, scanning electrochemical microscopy and scanning tunneling microscopy applied to the study of dsDNA binding and damage by scorpiand-like polyamine receptors

Abstract Microparticulate deposits of scorpiand-like azamacrocyclic receptors (L1–L4) attached to graphite electrodes provide distinctive voltammetric features in contact with aqueous DNA solutions at biological pH, denoting the formation of DNA surface complexes. This voltammetry allows for screening dsDNA, ssDNA and G-Quadruplex DNA using L4-modified electrodes. Scanning electrochemical microscopy and scanning tunneling microscopy examination of dsDNA fibers attached to the substrate electrode in contact with DMSO solutions containing ferrocene and receptor indicate that a synergic effect is exerted between electrochemically generated ferrocenium ion and the receptors so that they increas…

Access to Phylogeny from Voltammetric Fingerprints of Seeds: the Apsparagus Case

A methodology for characterizing vegetal taxonomic groups from the voltammetric fingerprints of polyphenolic components of seeds is described. It is based on recording the voltammetric response of microparticulate films deposited on glassy carbon electrodes from seed extracts using different organic solvents. The obtained responses in contact with aqueous electrolytes provided characteristic voltammetric profiles at the level of genera/subgenera and/or families using bivariant and multivariant chemometric methods. The voltammograms of 14 species from 5 different families provided family-characteristic patterns. Analysis of voltammetric responses for a set of 20 species of the Asparagus genu…

Harvesting canthinones: identification of the optimal seasonal point of harvest of Zanthoxylum chiloperone leaves as a source of 5-methoxycanthin-6-one

This article is focused on the seasonal variation in the contents of 5-methoxycanthin-6-one from the leaves of Zanthoxylum chiloperone (Rutaceae). Based on the pharmacological interest presented by 5-methoxycanthin-6-one, its seasonal variation in Z. chiloperone leaves was analysed in order to determine the best time for harvesting, optimising the 5-methoxycanthin-6-one content. The seasonal dynamics of canthinone alkaloids can be the key to improve the isolation from natural sustainable sources, such as leaves. Complementarily, this study describes the phytochemistry of leaf from this Ruraceae species.

FIB-FESEM and EMPA results on Antoninianus silver coins for manufacturing and corrosion processes

[EN] A set of ancient Antoninianus silver coins, dating back between 249 and 274¿A.D. and minted in Rome, Galliae, Orient and Ticinum, have been characterized. We use, for the first time, a combination of nano-invasive (focused ion beam-field emission scanning electron microscopy-X-ray microanalysis (FIB-FESEM-EDX), voltammetry of microparticles (VIMP)) and destructive techniques (scanning electron microscopy (SEM-EDX) and electron microprobe analysis (EMPA)) along with non-invasive, i.e., micro-Raman spectroscopy. The results revealed that, contrary to the extended belief, a complex Ag-Cu-Pb-Sn alloy was used. The use of alloys was common in the flourishing years of the Roman Empire. In th…

Correction of Matrix Effect in Multielemental Quantitative Analysis by X-Ray Fluorescence Spectroscopy Using the Linear Behavior in the Analytical Range of the Substitution-Dilution Method

This paper is an analytical study of the possibility of applying the linear range of the substitution-dilution method to correct the matrix effect in quantitative analysis by X-ray fluorescence (XRF) spectroscopy. The analytical range is obtained from a series of samples prepared in the form of glass discs by substituting the unknown sample with a standard sample (substitution factor, h) including a diluent-melt. In general, the substitution-dilution method is hyperbolic in character and therefore the diluent is required to ensure linear behavior between If vs. h in the experimental range. The linear range is located between the concentrations of standard and unknown for each element analy…

Response to “C. Tsiantos, M. Tsampodimou, G.H. Kacandes, M. Sánchez del Río, V. Gionis, G.D. Chryssikos. Comment to the paper: Identification of indigoid compounds present in archaeological Maya blue by pyrolysis-silylation-gas chromatography–mass spectrometry (M.T. Doménech-Carbó, L. Osete-Cortina, A. Doménech-Carbó, M.L. Vázquez de Agredos-Pascual, C. Vidal-Lorenzo, J. Anal. Appl. Pyrol. 105 (2014) 355–362)”

Effect of high levels of CO 2 on the electrochemical behavior and the enzymatic and non‐enzymatic antioxidant systems in black and white table grapes stored at 0 °C

[Bakghround]: In this study, we analyzed the effect of the application of high levels of CO2 (20 kPa CO2  + 20 kPa O2  + 60 kPa N2 ) for 3 days at low temperature on a white table-grape cultivar (Superior Seedless) in comparison with a black one (cv. Autumn Royal) in terms of quality parameters. We also used a solid-state voltammetry methodology to analyze the effect of the 3-day gaseous treatment in berry tissues from both cultivars in the first stage of storage. We determined the role of the non-enzymatic (total phenols, total anthocyanins, and antioxidant activity) and the enzymatic antioxidant (catalase (GCAT), ascorbate peroxidase (VcAPX) gene expression) systems in the behaviors of bo…

3D defective graphenes with subnanometric porosity obtained by soft-templating following zeolite procedures

[EN] By applying the well-known templating mechanism employed for the synthesis of mesoporous silicas to the structuration of sodium alginate, a novel defective 3D tubular graphene material (graphenolite) with hierarchical macro/meso/micro-porous structure, very high powder specific surface area (1820 m(2) g(-1)) and regular micropore size (0.6 nm) has been obtained. The key feature of the process is the filmogenic property of alginate that is able to replicate the liquid crystal rods formed by the CTAC template in the aqueous phase. The 3D graphene exhibits 2.5 times higher capacitance using Li+ electrolyte compared to K+, indicating that Li+ can ingress to the ultramicropores which, in co…

Dating archaeological copper/bronze artifacts by using the voltammetry of microparticles.

A method for dating copper/bronze archaeological objects aged in atmospheric environments is proposed based on the specific signals for cuprite and tenorite corrosion products measured through the voltammtry of microparticles method. The tenorite/cuprite ratio increased with the corrosion time and fitted to a potential law that yielded a calibration curve usable for dating purposes.

Evaluation of aging processes of petroleum asphalt cements by solid state electrochemical monitoring

Abstract The changes in the chemistry of organosulfur compounds from asphalt cements during aging are studied using solid state voltammetry of immobilized microparticles. Five Brazilian asphalt cements were evaluated after three forced aging processes: Rolling Thin Film Oven Test (RTFOT), Pressure Aging Vessel (PAV) and SUNTEST. It was possible to identify the presence of thiophenes, sulfides and sulfoxides in the different samples and the reactional changes during the aging processes were proposed. Voltammetric data, supported by ATR-FTIR spectroscopy, indicate that aging asphalts involve the increase of the proportion of sulfoxide and thiophene components and that polythiophene compounds …

Rise and fall of historic tram networks: Logistic approximation and discontinuous events

Abstract A logistic approximation was used to describe, in terms of total length (L) and population (H) variables, the growth and decay of historic transportation systems. Three successive stages, separated for sharp discontinuities were detected for several European tramway and metro systems, corresponding to a fast initial growth followed by an intermediate step of slow growth and a final stage of rapid decay. A common, generalized behaviour was obtained in the L/H vs. H variations relative to critical values of L and H parameters defined from the maximum in the L/H ratio.

Solvent-Independent Electrode Potentials of Solids Undergoing Insertion Electrochemical Reactions: Part III. Experimental Data for Prussian Blue Undergoing Electron Exchange Coupled to Cation Exchange

Prussian blue-modified electrodes immersed in K+-containing solutions can be used to obtain a solvent-independent redox potential system. On the basis of theoretical modeling of diffusion processes occurring under the conditions of voltammetry of immobilized particles, voltammetric and chronoamperometric data can be combined to obtain solvent-independent electrode potentials for the K+-assisted one-electron reduction of Prussian blue to Berlin white. Data for water, MeOH, EtOH, MeCN, DMS, DMF, and NM are provided.

Quantitation of Metal Ions in Archaeological Glass by Abrasive Stripping Square-Wave Voltammetry Using Graphite/Polyester Composite Electrodes

A method for identifying Co, Cu, Sb, Sn, Fe, Zn, and Zr pigments in glasses using square-wave voltammetry as the detection mode is described. It is based on the abrasive attachment of glass microsamples to graphite/polyester composite electrodes. Sample amounts less than 1 μg are used allowing for the study of archaeological samples. In all cases well-defined anodic stripping peaks corresponding to the oxidation of metal deposits generated at potentials ranging from −0.6 to −1.6 V (vs. SCE) are obtained. This response is in agreement with that displayed by the corresponding metal oxides. Quantitative estimates of the relative population of metal ions in glasses are obtained from peak area m…

Identification of vegetal species in wooden objects using in situ microextraction-assisted voltammetry of microparticles

[EN] A method for identifying vegetal species in wooden objects using microextraction-assisted voltammetry of microparticles is described. The proposed methodology, aimed at facilitating tasks of patrimony conservation, is based on the recording of the voltammetric response of microparticulate films of compounds resulting from microextraction with organic solvents (ethanol, acetone, and chloroform) of micro- or sub-microsamples of wood in contact with aqueous buffers. Upon application of bivariate and multivariate chemometric techniques, the obtained voltammetric responses led us to identify different taxonomic groups from the characteristic voltammetric profiles. Application to a series of…

Identification of indigoid compounds present in archaeological Maya blue by pyrolysis-silylation-gas chromatography–mass spectrometry

Abstract A study based on the use of pyrolysis-silylation-gas chromatograpy–mass spectrometry (Py-GC–MS), which aimed to identify indigoid compounds and to clarify the multicomponent composition of Maya blue (MB) pigment, has been carried out. A series of reference compounds and synthetic MB specimens prepared in the laboratory have been analysed by this technique. An analysis of archaeological MB samples from 14 Maya archaeological sites from Mexico and Guatemala has also been performed. The obtained results demonstrate that, in addition to indigo, oxidised species such as dehydroindigo, which is formed as a result of redox processes taking place while preparing the pigment, are present in…

Coordination Chemistry of Cu2+ Complexes of Small N-Alkylated Tetra-azacyclophanes with SOD Activity

A new tetraaza-pyridinophane macrocycle (L1) N-alkylated with two isopropyl and one methyl groups symmetrically disposed has been prepared and its behavior compared with those of the unsubstituted pyridinophane (L3) and the related compound with three methyl groups (L2). The protonation studies show that, first, a proton binds to the central methylated amine group of L1, while, second protonation leads to a reorganization of the protons that are at this stage attached to the lateral isopropylated amines. The X-ray structure of [HL1]+ agrees with the UV–vis and NMR studies as well as with the results of DFT calculations. The stability of the Cu2+ complexes decreases on increasing the bulkine…

Electrochemical Characterization of Coinage Techniques the 17(th) Century: The maravedis Case

[EN] The voltammetry of immobilized particles (VIMP) methodology was applied to the discrimination of Spanish maravedis produced in 10 different mints between 1661 and 1664 using characteristic signatures for the reduction of cuprite and tenorite in the patina of the coins and catalytic effects on the hydrogen evolution reaction (HER). The variation of the apparent tenorite/cuprite ratio with depth was fitted to potential laws differing from one mint to another for A Coruna, Burgos, Cordoba, Cuenca, Granada, Madrid, Trujillo, Segovia, Sevilla and Valladolid coins. Electrochemical data permitted to detect the changes in the composition (with lowering of the silver content) and manufacturing …

Analysis of rolling friction effects on oblique rebound by redefining tangential restitution and friction

The planar oblique impact of a homogeneous sphere on an infinitely massive rough plane is described assuming that normal and tangential restitution mechanisms operate independently of friction, and that frictional effects include not only the usual Coulomb model but also rolling friction effects. This formulation extends early models including rolling friction effects in the description of impact events to include the independent friction restitution closure. The model yields velocity-independent equations for postimpact linear and angular velocities in four impact regimes, namely, sliding plus rolling, sliding nonrolling, stick plus rolling, and stick nonrolling whose predictions are compa…

Caracterización electroquímica del proceso de degradación de materiales piritosos en colecciones geológicas y paleontológicas: propuestas de tratamiento y conservación

Este trabajo analiza los problemas de conservación y tratamiento de ejemplares paleontológicos y geológicos en los museos centrándonos en ejemplares piritizados, destacando los principales factores que afectan la preservación de este tipo de colecciones. Se ha realizado una intervención en ejemplares paleontológicos y geológicos en la cual han sido tratados para su adecuada conservación. Para caracterizar el proceso de degradación se ha realizado un estudio electroquímico sobre diversos ejemplares conservados en pirita y, de este modo, poder identificar estadios de la degradación presente de los ejemplares (producida en el curso del almacenamiento y conservación). La identificación de estos…

Supramolecular Construction of Cyanide-Bridged Re I Diimine Multichromophores

The reactions of labile [Re(diimine)(CO)3(H2O)]+ precursors (diimine = 2,2′-bipyridine, bpy; 1,10-phenanthroline, phen) with dicyanoargentate anion produce the dirhenium cyanide-bridged compounds [{Re(diimine)(CO)3}2CN)]+ (1 and 2). Substitution of the axial carbonyl ligands in 2 for triphenylphosphine gives the derivative [{Re(phen)(CO)2(PPh3)}2CN]+ (3), while the employment of a neutral metalloligand [Au(PPh3)(CN)] affords heterobimetallic complex [{Re(phen)(CO)3}NCAu(PPh3)]+ (4). Furthermore, the utilization of [Au(CN)2]−, [Pt(CN)4]2–, and [Fe(CN)6]4–/3– cyanometallates leads to the higher nuclearity aggregates [{Re(diimine)(CO)3NC}xM]m+ (M = Au, x = 2, 5 and 6; Pt, x = 4, 7 and 8; Fe, x…

Uniform nanoporous graphene sponge from natural polysaccharides as a metal-free electrocatalyst for hydrogen generation

[EN] Structuring of graphene as graphene sponges in the submicrometric scale has been achieved by using silica spheres (80 nm diameter) as hard templates and chitosan or alginate as precursor of defective N-doped or undoped graphene, respectively. The resulting defective N-doped graphene sponge exhibits a remarkable activity and stability for hydrogen evolution reaction with onset at 203 mV for a current density of 0.5 mA cm(-2) with a small Tafel plot slope of 69.7 mV dec(-1). In addition, the graphene sponge also exhibits a high double layer capacitance of 11.65 mF cm(-2). Comparison with an analogous N-doped graphene sample shows that this electrochemical properties derive from the spati…

Electrochemical analysis of the alterations in copper pigments using charge transfer coefficient/peak potential diagrams. Application to microsamples of baroque wall paintings attached to polymer film electrodes

The alteration of copper pigments in art samples was studied by linear scan and cyclic voltammetry using sample-modified Elvacite 2044 film electrodes on the basis of two-dimensional diagrams of charge transfer coefficients calculated from Tafel plots of reductive dissolution processes vs. peak potential. Characteristic voltammetric peaks were obtained for pigments used in the baroque vault frescoes of the Basílica de la Virgen de los Desamparados painted by Antonio Palomino. Results obtained by voltammetric techniques were compared with those from SEM/EDX and FT-IR analysis obtaining a good agreement and leaving to an unambiguous identification of pigments used by Palomino and their altera…

ATR-FTIR and XRD quantification of solid mixtures using the asymptotic constant ratio (ACR) methods. Application to geological samples of sodium and potassium feldspars

Two asymptotic constant ratio methods applied to the quantification of individual components of solid samples using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD) are described. The methods involve the measurement of the peak current/peak areas of selected signals (diffraction peaks in XRD and absorption bands in ATR-FTIR) relative to the signal of standard added in constant proportion to the sample and the sample enriched with the analyte following the usual standard additions methodology. The proposed method compensates the absorption effects appearing in XRD and the presence of overlapping absorption bands of interferents by me…

An innovative multi-analytical approach based on spectroscopic and electrochemical techniques to study a complex Roman amphorae collection

Abstract An innovative multi-analytical approach for the classification of ancient pottery sherds was tested. Twenty Roman amphorae fragments belonging to different known typologies and twenty-seven unclassified ones from a complex Sagunto Archaeological Museum (Spain) collection were studied by multielement analysis (X-ray fluorescence spectroscopy and inductively coupled plasma mass spectrometry), Fourier-transform near infrared spectroscopy and voltammetry of immobilized microparticles employing a minimal amount of sample. Chemometric analysis based on principal component analysis allowed the identification of most of the unclassified samples, proving the importance and reliability of th…

Dating of Archaeological Gold by Means of Solid State Electrochemistry

[EN] In archaeology and history of art, age determination is a fundamental analytical problem. While several techniques for age determination of various materials, like radiocarbon dating, are established, these methods cannot be applied for metals, for which new techniques have to be developed. For the first time a dating method for archaeological gold objects is described which is based on a corrosion clock and electrochemical measurements, using the voltammetry of immobilized particles. Samples are prepared by one touch' with a graphite pencil, only transferring a few nanograms of the archaeological gold. The method has been calibrated with the help of a series of well-documented gold sp…

Electrodes with Immobilized Particles and Droplets: Three-Phase Electrodes

It is a common feature of electrodes with immobilized particles and droplets that three phases are in close contact with each other, i.e., each phase having an interface with the two other phases. This situation exists also in most of the so-called surface-modified or film electrodes, many battery and fuel cell electrodes, electrodes of the second kind, etc. In fact, the majority of surface-modified electrodes consist of arrays of particles that partially cover the electrode surface. It would be far beyond the scope of this book to include all chemical and electrochemical techniques to deposit films on electrodes. Here we shall deal only with electrodes where the particles or droplets have …

Electrochemical Determination of the Fe(III)/Fe(II) Ratio in Archaeological Ceramic Materials Using Carbon Paste and Composite Electrodes

A method for determining the iron(III)/iron(II) ratio in ceramic materials based on microsample attachment to graphite/polyester composite electrodes is presented. This quotient is of considerable interest for determining the nature and firing conditions of the original materials in archaeological ceramics. The electrochemistry of iron in ceramic materials in acetic/acetate and Na2EDTA aqueous solutions is described in terms of reductive dissolution processes of iron(III) materials and oxidative dissolution processes of iron(II) ones. The iron(III)/iron(II) ratio is determined from peak area measurements in linear scan voltammograms performed in 0.10 M acetic/acetate buffer (pH 4.70) and 0.…

Unique distal size selectivity with a digold catalyst during alkyne homocoupling

Metal-catalysed chemical reactions are often controlled by steric hindrance around the metal atom and it is rare that substituents far away of the reaction site could be differentiated during reaction, particularly if they are simple alkyl groups. Here we show that a gold catalyst is able to discriminate between linear carbon alkynes with 10 or 12 atoms in the chain during the oxidative homocoupling of alkynes: the former is fully reactive and the latter is practically unreactive. We present experimental evidences, which support that the distal size selectivity occurs by the impossibility of transmetallating two long alkyl chains in an A-framed, mixed-valence digold (I, III) acetylide compl…

An electrochemical analysis suggests role of gynodioecy in adaptation to stress in Cortaderia selloana

Cortaderia selloana is an invasive, gynodioecious species prevalent in Mediterranean area which contains both female and hermaphrodite specimens in the wild population. Using voltammetric data we show that the female and hermaphrodite specimens exhibit differential electrochemical response. Cortaderia selloana leaves from two different provenances in the Valencia Mediterranean area, Sueca and Cullera (Comunitat Valenciana, Spain), in the surroundings of the Albufera Natural Park, a peculiar ecosystem containing unspoilt dune beaches and forests, were studied to determine correlation of flower morphology with the plant's ability to adapt to stress conditions. Our data suggests that gynodioec…

Cover Feature: Few‐layer Black Phosphorous Catalyzes Radical Additions to Alkenes Faster than Low‐valence Metals (ChemCatChem 8/2020)

Ambipolar Phosphine Derivatives to Attain True Blue OLEDs with 6.5% EQE

A family of new branched phosphine derivatives {Ph2N-(C6H4)n-}3P → E (E = O 1-3, n = 1-3; E = S 4-6, n = 1-3; E = Se 7-9, n = 1-3; E = AuC6F5 4-6, n = 1-3), which are the donor-acceptor type molecules, exhibit efficient deep blue room temperature fluorescence (λem = 403-483 nm in CH2Cl2 solution, λem = 400-469 nm in the solid state). Fine tuning the emission characteristics can be achieved varying the length of aromatic oligophenylene bridge -(C6H4)n-. The pyramidal geometry of central R3P → E fragment on the one hand disrupts π-conjugation between the branches to preserve blue luminescence and high triplet energy, while on the other hand provides amorphous materials to prevent excimer form…

Electrochemical detection and screening of bladder cancer recurrence using direct electrochemical analysis of urine: A non-invasive tool for diagnosis

Although detection of urothelial cell carcinoma (or bladder cancer, BC) can be performed via cytological, molecular and genetic marker tests on urine, cystoscopy, an invasive technique, still remains as the gold methodology in clinical practice. It is presented a non-invasive method for detecting BC recurrence consisting of a direct electrochemical test in urine combining voltammetric data at gold and glassy carbon electrodes. The diagnosis is based on the ratio between characteristic voltammetric features recorded for tryptophan, serotonin and melatonin and other related metabolites. The method was tested by means of a clinical trial with 30 patients diagnosed of bladder cancer and a two c…

Identification of lead pigments in nanosamples from ancient paintings and polychromed sculptures using voltammetry of nanoparticles/atomic force microscopy.

Voltammetry of nanoparticles coupled with atomic force microscopy was used to identify lead pigments in nanosamples proceeding from works of art. Upon mechanical attachment of few nanograms of sample to a graphite plate, well-defined voltammetric responses were obtained for lead orange, lead yellow, lead white, litharge, minium, Naples yellow, and tin-lead yellow, allowing for an unambiguous identification of such pigments. Atomic force images provide evidence for the occurrence of pigment-characteristic reduction processes accompanied by metal deposition on the graphite substrate. Electrochemical parameters are used for pigment identification. Application to the method for identifying lead…

Standard additions-dilution method for absolute quantification in voltammetry of microparticles. Application for determining psychoactive 1,4-benzodiazepine and antidepressants drugs as adulterants in phytotherapeutic formulations

A standard additions-dilution solid-state electrochemical method for the determination of psychoactive 1,4-benzodiazepine and antidepressants drugs used as adulterants in commercial slimming herbal formulations is described and compared with conventional standard addition method. The proposed method, based on the voltammetry of microparticles approach, permits quantify, via standard additions methodology, 1,4-benzodiazepine and antidepressants drugs in phytotherapeutic formulations with no need of sample dissolution using dilution with a reference electroactive compound. The method was used to measure 1,4-benzobenzodiazepines (clonazepam, flurazepam, alprazolam, midazolam, bromazepam, chlor…

Discovery of indigoid-containing clay pellets from La Blanca: significance with regard to the preparation and use of Maya Blue

Analytical studies using extraction/liquid chromatography, pyrolysis–silylation gas chromatography–mass spectrometry, visible and infrared spectroscopies, solid state voltammetry and electron microscopy on a set of spherical greenish pellets discovered in the Structure 4H1 of the ancient Maya site of La Blanca (Peten Department, Guatemala), dated in the Terminal Classic period, confirm the presence of indigoids (dehydroindigo, indigo) associated to palygorskite. The appearance of such pieces, whose origin and function is uncertain, but most likely correspond to residuals of a decorative plaster, can be considered as indicative of the use of Maya Blue in a quotidian context, thus suggesting …

Discrimination of papers used in conservation and restoration by the means of the voltammetry of immobilized microparticles technique

Herein, voltammetry of immobilized microparticles (VIMP) is employed for the discrimination of papers used in the conservation and restoration field. The electrochemical parameters are used for the discrimination of different samples coming from China, Japan and Korea. The method is based on the recording of the voltammetric response of microparticulate deposits from acetone extracts of paper samples deposited on a glassy carbon electrode in contact with 1.0 M H2SO4. The voltammetric responses attributed to the lignin and the oxidation products of the cellulose were collected and are discussed. The grouping of samples was obtained upon the application of the chemometric methods, as well as …

Ageing behaviour and analytical characterization of the Jatobá resin collected from Hymenaea stigonocarpa Mart.

Abstract This paper reports the results of an analytical study to characterize the trunk resin collected from the Hymenaea stigonocarpa Mart. species from the region of Minas Gerais (Brazil), popularly known as Jatoba resin. Hymenaea resins are reported to have been used in artistic applications such as protective varnishes in polychromed sculptures and paintings. Therefore, the identification of the main chemical changes that take place in the resin when it is prepared as a thin film exposed to atmospheric effects have been considered herein. Changes due to the degradation effect of light have been studied on a series of specimens prepared as a thin films and subjected to accelerated UV li…

Electroanalytical techniques in archaeological and art conservation

[EN] The application of electrochemical techniques for obtaining analytical information of interest in the fields of archaeometry, conservation and restoration of cultural heritage goods is reviewed. Focused on voltammetry of immobilised particles and electrochemical impedance spectroscopy techniques, electrochemical measurements offer valuable information for identifying and quantifying components, tracing provenances and manufacturing techniques and provide new tools for authentication and dating.

Detection of archaeological forgeries of Iberian lead plates using nanoelectrochemical techniques. The lot of fake plates from Bugarra (Spain)

Identification of forgeries is of considerable interest in studies of archaeological signariums and written Iberian artifacts, elements of capital importance for the knowledge of that culture, because there are many Iberian inscribed lead plate counterfeits circulating in the market and among many museum funds. A case study of identification of forgeries of archaeological lead using voltammetry of microparticles (VMP) and scanning electrochemical microscopy (SECM), aided by conventional optical microscopy and scanning electron microscopy (SEM/EDX) is described. The electrochemical methods are essentially non-invasive so can be applied to samples of nanoscopic size. Application to the authen…

Polystyrene as Graphene Film and 3D Graphene Sponge Precursor

[EN] Polystyrene as a thin film on arbitrary substrates or pellets form defective graphene/graphitic films or powders that can be dispersed in water and organic solvents. The materials were characterized by visible absorption, Raman and X-ray photoelectron spectroscopy, electron and atomic force microscopy, and electrochemistry. Raman spectra of these materials showed the presence of the expected 2D, G, and D peaks at 2750, 1590, and 1350 cm(-1), respectively. The relative intensity of the G versus the D peak was taken as a quantitative indicator of the density of defects in the G layer.

Electrochemistry of Iron-Doped Zircon and Zirconia Materials and Electrocatalytic Effects on Nitrite Oxidation and Reduction

Electrochemical analysis of the first Polish coins using voltammetry of immobilized particles

[EN] A series of 20 denarii from Boleslaus the Brave (992-1025) and Mieszko II Lambert (1025-1034), corresponding to the beginning of the Polish state were studied using the voltammetry of immobilized particles (VIMP) methodology. VIMP experiments, applied to nanosamples of the corrosion layers of the coins in contact with aqueous acetate buffer, provided well-defined responses mainly corresponding to the corrosion products of copper and lead. Such voltammetric responses, combined with X-ray fluorescence (XRF) spectroscopy experiments performed on the same set of coins, and complemented by focusing ion beam-field emission scanning electron microscope (FIB-FESEM) on silver coins from the 19t…

Cation and anion electrochemically assisted solid-state transformations of malachite green

[EN] The possibility of the electrochemical promotion of different solid-to-solid transformations including the performance of successive cation and anion insertion processes has been tested using malachite green, a triphenylmethane dye, in contact with aqueous NaCl electrolyte. Electrochemical data using the voltammetry of microparticles methodology reveal significant differences with the solution phase electrochemistry of the dye. Voltammetric data, combined with atomic force microscopy, focusing ion beam-field emission scanning electron microscopy, and high-resolution field emission scanning electron microscopy permit characterization of the oxidative dissolution, oxidation with anion in…

‘Maya chemistry’ of organic–inorganic hybrid materials: isomerization, cyclicization and redox tuning of organic dyes attached to porous silicates

[EN] Association of indigo and lapachol dyes to aluminosilicate clays yields polyfunctional organic – inorganic hybrid materials forming Maya Blue-like systems. Upon partial removing of clay's zeolitic water by moderate thermal treatment, abundant isomerization, cyclicization and oxidation reactions occur defining a‘ Maya chemistry whose complexity could explain the versatile use of such materials in the pre-Columbian cultures and permits the preparation of polyfunctional materials potentially usable for therapeutic and catalytic purposes.

The Thermodynamics of Insertion Electrochemical Electrodes—A Team Play of Electrons and Ions across Two Separate Interfaces

Insertion electrochemical electrodes exhibit simultaneous electron and ion transfer, with the two transfers proceeding across different interfaces. Herein the thermodynamics of the overall electrochemical electrode reaction is discussed with respect to the thermodynamics of these two charge-transfer equilibria. This Minireview includes insertion electrochemical systems where the redox centers are in a solid phase and the ions are transferred between that phase and a solution, and also systems where the redox centers are in a liquid phase that is immiscible with another liquid phase and ions are transferred between the two liquid phases. The Minireview is intended to spark similar studies on…

Biosynthesis of heme O in intraerythrocytic stages of Plasmodium falciparum and potential inhibitors of this pathway

A number of antimalarial drugs interfere with the electron transport chain and heme-related reactions; however, the biosynthesis of heme derivatives in Plasmodium parasites has not been fully elucidated. Here, we characterized the steps that lead to the farnesylation of heme. After the identification of a gene encoding heme O synthase, we identified heme O synthesis in blood stage parasites through the incorporation of radioactive precursors. The presence of heme O synthesis in intraerythrocytic stages of Plasmodium falciparum was confirmed by mass spectrometry. Inabenfide and uniconazole–P appeared to interfere in heme synthesis, accordingly, parasite growth was also affected by the additi…

In situ AFM study of proton-assisted electrochemical oxidation/reduction of microparticles of organic dyes

In situ atomic force microscopy (AFM) images of crystals of organic dyes alizarin, indigo and morin have been monitored during the course of their solid-state electrochemical oxidation/reduction in contact with aqueous acetate buffer. Such images indicate that proton-assisted reduction and oxidation processes are localized in a shallow layer in the vicinity of the particle/electrolyte interface, in agreement with expectances from the Lovric and Scholz model with significantly restricted proton diffusion across the solids. Keywords: Voltammetry of nanoparticles, Atomic force microscopy, Organic dyes, Diffusion

Identification by GC-FID and GC-MS of amino acids, fatty and bile acids in binding media used in works of art.

GC-FID was used as single methodology for the identification and differentiation of proteins, lipids and ox bile from binders used in artistic paintings. The samples were hydrolyzed by HCl. Subsequently, the simultaneous formation of volatile derivatives of the amino, fatty and bile acids with ethyl chloroformate was performed quickly and safely in an aqueous medium. The derivatives were separated by capillary GC and characterized by GC-MS. The ageing of drying oils was studied, identifying pelargonic acid among other degradation products. Proteinaceous and lipoid binding media were characterized by means of the quotients between the areas of the peaks for each amino or fatty acid with resp…

On-line database of voltammetric data of immobilized particles for identifying pigments and minerals in archaeometry, conservation and restoration (ELCHER database)

[EN] A web-based database of voltammograms is presented for characterizing artists' pigments and corrosion products of ceramic, stone and metal objects by means of the voltammetry of immobilized particles methodology. Description of the website and the database is provided. Voltammograms are, in most cases, accompanied by scanning electron microphotographs, X-ray spectra, infrared spectra acquired in attenuated total reflectance Fourier transform infrared spectroscopy mode (ATR-FTIR) and diffuse reflectance spectra in the UV-Vis-region. For illustrating the usefulness of the database two case studies involving identification of pigments and a case study describing deterioration of an archae…

Corrigendum to “ATR-FTIR and XRD quantification of solid mixtures using the asymptotic constant ratio (ACR) methods. Application to geological samples of sodium and potassium feldspars” [Spectrochim. Acta A 236 (2020) 118328]

Solid-State Electrochemical Assay of Heme-Binding Molecules for Screening of Drugs with Antimalarial Potential

The interaction between heme and ligands is the basis for a variety of tests aimed at the discovery of antiplasmodial molecules. Two electrochemical methods for the screening of molecules with potential antimalarial activity through heme-binding mechanism are described. The first method is applicable to lipophilic environment, by using solution phase electrochemistry in DMSO solutions of Fe(III)-heme plus the tested compounds at carbon electrodes. This method provides well-defined voltammetric signals, characteristic of the heme-ligand (L) interaction. The second method involves aqueous media at biological pH and the use of voltammetry of immobilized particles, by means of microparticulate …

Preparation of body colors in Pre-classical Maya culture: the red pigment in the 19th tomb (Peten, Guatemala)

The pigments were important in the funerary customs of the ancient Maya. They could be introduced as an offering inside the tombs or burials, and were also used to wrap the dead bodies, as if it were a funeral shroud. In the tombs and burials of royalty and high social classes the use of pigments for this purpose is well documented, and physicochemical studies are focused on their identification. This scientific contribution shows the results obtained when analyzing two reddish pigmenting materials from the grave goods of the tomb 19 of the archaeological site of Rio Azul, (Guatemalan Department of Petén), using a multi-technique approach including microscopy, diffraction, spectroscopic, el…

dsDNA, ssDNA, G-quadruplex DNA, and nucleosomal DNA electrochemical screening using canthin-6-one alkaloid-modified electrodes

Abstract Microparticulate films of a canthin-6-one alkaloid ( L ), a natural β-carboline alkaloid presenting a characteristic naphtyridone motif, on glassy carbon electrodes yield different, separate voltammetric signals for dsDNA, ssDNA, G-quadruplex DNA, different degrees of DNA methylation and the biomimetic nucleosomal DNA with detection limit of 10 −5  M. This multiple-signal electrochemical behavior is in contrast with conventional use of DNA intercalators, only discriminating between different DNA forms by variations in the intensity of a unique signal. Complementary photochemical and scanning electrochemical microscopy (SECM) data suggest that the differences in the voltammetric res…

Oxidative stress protection by manganese complexes of tail-tied aza-scorpiand ligands.

The Mn2+ coordination chemistry of double scorpiand ligands in which two polyazacyclophane macrocycles have been connected by pyridine, phenanthroline and bipyridine spacers has been studied by potentiometry, paramagnetic NMR and electrochemistry. All ligands show high stability with Mn2+ and the complexes were formed in a wide pH range. DFT calculations support the structures and coordination geometries derived from the study. A remarkable antioxidant activity was evidenced for these systems by the McCord-Fridovich assay and in Escherichiacoli sodAsodB deficient bacterial cells. The three systems were tested as anti-inflammatory drugs in human macrophages measuring the accumulation of cyto…

Analytical study of proteinaceous binding media in works of art by gas chromatography using alkyl chloroformates as derivatising agents.

In this work, we present the results obtained in an analytical study of the different types of proteinaceous binding media most commonly used in paintings, using GC-FID as the technique of analysis and GC-MS as a confirmatory technique. The application of this methodology requires prior hydrolysis of the proteins in the binding media to obtain free amino acids and then volatile derivatives, in this case by reaction with chloroformates due to advantages of speed, safety and the aqueous medium in which the reaction occurs. The method proposed for the proteinaceous binding media study is to calculate the proportions of the different amino acids with respect to alanine. This method provided goo…

Earlier Developed Techniques

The first electrochemical experiments were performed with solid materials, esp. metals. However, these experiments, conducted in the eighteenth and nineteenth centuries, were directed toward the elucidation of the basic features of the electrical action of chemical substances and the chemical action of electricity. Initially, metals played the major role; only later it became obvious that many chemical compounds possess metallic or semiconducting properties that can be utilized in electrochemical cells. Parallel to the studies of new electrode materials, solid electrolytes were discovered and entire solid galvanic cells could be constructed. In this book, we will entirely neglect pure solid…

Analytical and mineralogical studies of ore and impurities from a chromite mineral using X-ray analysis, electrochemical and microscopy techniques

A wide analytical study of South African chromite ore, material with high interest in ceramic industry, has been carried out. With this purpose, an accurate chemical identification and mineralogical characterization of the mineral and the gangue have been performed using X-ray fluorescence (XRF), voltammetry, X-ray diffraction (XRD), light microscopy (LM), and scanning electron microscopy (SEM/EDX). The elemental composition of the sample (ore and gangue) has been obtained by XRF. The voltammetric analysis has allowed to demonstrate that iron in the sample was as Fe(II). The main compound of the chromite ore was a spinel (magnesiochromite ferroan), identified by XRD from the sample, which c…

Acid Catalysis with Alkane/Water Microdroplets in Ionic Liquids

Ionic liquids are composed of an organic cation and a highly delocalized perfluorinated anion, which remain tight to each other and neutral across the extended liquid framework. Here we show that n-alkanes in millimolar amounts enable a sufficient ion charge separation to release the innate acidity of the ionic liquid and catalyze the industrially relevant alkylation of phenol, after generating homogeneous, self-stabilized, and surfactant-free microdroplets (1–5 μm). This extremely mild and simple protocol circumvents any external additive or potential ionic liquid degradation and can be extended to water, which spontaneously generates microdroplets (ca. 3 μm) and catalyzes Brönsted rather …

Electrochemical identification of metal ions in archaeological ceramic glazes by stripping voltammetry at graphite/polyester composite electrodes

The electrochemical response of metal ions in different samples of coloured ceramic tin-lead glazes attached to graphite/polyester composite electrodes is described. In addition to the ubiquous signals for lead, reductive dissolution processes are followed by anodic stripping peaks for Co, Cu, Sb, Mn, Sn and Fe, enabling the direct identification of such elements in microsamples proceeding from archaeological glazed tiles from Valencia (Spain) workshops (16th-18th century). Additional anodic and cathodic peaks corresponding to redox processes involving metal species in solution generated during stripping processes are also used. Peak potentials, Tafel plots and shape parameters are used for…

Die Thermodynamik von insertionselektrochemischen Elektroden – ein Mannschaftsspiel über zwei separate Grenzflächen

Polythiophenes as markers of asphalt and archaeological tar pitch aging. Characterization using solid-state electrochemistry

The voltammetry of immobilized microparticles (VIMP) was used to characterize organosulfur components from ovens found at the Spanish archaeological sites of Cueva de Nerja (ca. 35,000cal BC), la Illeta dels Banyets (4th century BCE) and Gestalgar (12th–13th CE), and asphalt probes subjected to PAV and SUNTEST aging protocols. The voltammetric responses of the archaeological samples and the asphalt probes after photodegradation were quite similar, indicating the presence of polythiophene components which could act as age/degradation markers. Keywords: Voltammetry, Archaeology, Asphalt, Tar pitch, Organosulfur compounds

Partial Reduction and Selective Transfer of Hydrogen Chloride on Catalytic Gold Nanoparticles

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim HCl in solution accepts electron density from Au NPs and partially reduces at room temperature, as occurs with other simple diatomic molecules, such as O2 and H2. The activation can be run catalytically in the presence of alkynes to give exclusively E-vinyl chlorides, after the regio- and stereoselective transfer of HCl. Based also on this method, vinyl chloride monomer (VCM) can be produced in a milder and greener way than current industrial processes.

Redox tuning and species distribution in Maya Blue-type materials: a reassessment.

Maya Blue-type specimens prepared from indigo (1 wt %) plus kaolinite, montmorillonite, palygorskite, sepiolite, and silicalite are studied. Liquid chromatography with diode array detection, ultra-performance liquid chromatography coupled with mass spectrometry, and pyrolysis-silylation gas chromatography-mass spectrometry analyses of the extracts from these specimens combined with spectral and solid-state voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy techniques provide evidence for the presence of a significant amount of dehydroindigo and isatin accompanying indigo and other minority organic compounds in all samples. Solid-state electrochemist…

Electroanalytical chemistry for the analysis of solids: Characterization and classification (IUPAC Technical Report)

Solid state electroanalytical chemistry (SSEAC) deals with studies of the processes, materials, and methods specifically aimed to obtain analytical information (quantitative elemental composition, phase composition, structure information, and reactivity) on solid materials by means of electrochemical methods. The electrochemical characterization of solids is not only crucial for electrochemical applications of materials (e.g., in batteries, fuel cells, corrosion protection, electrochemical machining, etc.) but it lends itself also for providing analytical information on the structure and chemical and mineralogical composition of solid materials of all kinds such as metals and alloys, variou…

Raman spectroscopy characterization of 10-cash productions from the late Chinese emperors to the Republic

[EN] The use of Raman spectroscopy for discriminating monetary emissions, a recurrent problem in much archaeological studies, is described. The method involves the record of Raman signatures of tenorite and crystalline and defective cuprite in the patina based on the idea that subtle, mint-characteristic variations in the composition and metallography of the base metal during the manufacturing process are reflected in the variation in depth of the composition and crystallinity of the corrosion patina. The technique was applied to a series of 10-cash copper coins produced around the transition between the Kuang Hsu and Hsuan Tung last Chinese emperors and the first Republic whose averaged co…

Quantification of minerals from ATR-FTIR spectra with spectral interferences using the MRC method.

A method for quantifying the individual components of mineral samples based on attenuated total reflectance - Fourier transform infrared spectroscopy (ATR-FTIR) is described, extending the constant ratio (CR) method to analytes absorbing in a common range of wavenumbers. Absorbance values in the spectral region where the analytes absorb relative to the absorbance of an internal standard absorbing at a wavenumber where the analytes do not absorb, permits the quantification of N analytes using measurements at N fixed wavenumbers. The method was tested for mixtures of albite, orthoclase, kaolin and quartz.

Archaeometric analysis of Roman bronze coins from the Magna Mater temple using solid-state voltammetry and electrochemical impedance spectroscopy

Voltammetry of microparticles (VMP) and electrochemical impedance spectroscopy (EIS) techniques, complemented by SEM-EDX and Raman spectroscopy, were applied to a set of 15 Roman bronze coins and one Tessera from the temple of Magna Mater (Rome, Italy). The archaeological site, dated back between the second half and the end of the 4th century A.D., presented a complicated stratigraphic context. Characteristic voltammetric patterns for cuprite and tenorite for sub-microsamples of the corrosion layers of the coins deposited onto graphite electrodes in contact with 0.10 M HClO4 aqueous solution yielded a grouping of the coins into three main groups. This grouping was confirmed and refined usin…

Electrochemical Age Determinations of Metallic Specimens—Utilization of the Corrosion Clock

Dating needs an age-dependent phenomenon (a "clock"), a procedure for monitoring the advance of time by measuring a physicochemical quantity, and, in the case of archeological artifacts, a sampling procedure that guarantees the representativity and integrity of the dated objects. Metal corrosion in an aerobic atmosphere is a phenomenon whose advance can in principle be used as a clock that depends on the environmental conditions. In spite of the limitation imposed by differences in local conditions of corrosion, a new approach for age determinations has been developed and applied as a feasible tool for age determinations of metallic specimens studied by archeologists and historians. These t…

Cover Picture: Access to Phylogeny from Voltammetric Fingerprints of Seeds: the Asparagus Case (Electroanalysis 2/2017)

Asymptotic modeling of electrochemical signaling: Testing Zn in urine for non-invasive bladder cancer diagnosis

Abstract A theoretical model on chemical signaling for diagnosis based on the combination of signals for marker and inert and/or interfering metabolites is described. The model yields asymptotic relationships between the intensities of the signals representative of marker and accompanying metabolites compensating concentration fluctuations. The model fits well with voltammetric features associated to the oxidation of different urine metabolites and Zn(II) reduction in the same urine samples after alkaline digestion. As a result, a non-invasive electrochemical detection of urothelial carcinoma (bladder cancer, BC) is reported. Different diagnostic criteria are described all displaying high s…

Microchemical surface analysis of historic copper-based coins by the combined use of FIB-FESEM-EDX, OM, FTIR spectroscopy and solid-state electrochemical techniques

[EN] A multi-technique strategy, including microscopy, spectroscopic and electrochemical techniques, is proposed to study thin corrosion layers that form on the surface of historic copper-based coins. An accurate characterisation of this external corrosion layer is important for selecting a suitable conservation and/or restoration treatment. For this purpose, a series of copper-based coins from different historical periods and provenances, which mainly exhibited atmospheric corrosion, was analysed. The morphology of the corrosion layer and the upper core of coins was studied in trenches done on coin surfaces with a focused ion beam gun, coupled to a field emission scanning electron microsco…

Transmembrane electrochemistry of erythrocytes: Direct electrochemical test for detecting hemolysis in whole blood

A rapid method for detecting hemolysis in whole blood based on a direct electrochemical assay either in venous blood and finger blood, respectively at glassy carbon and screen-printed graphite electrodes is described. The presence of hemolysis is detected from characteristic voltammetric signatures associated to Fe-heme units in healthy and hemolyzed erythrocytes. The voltammetric response of blood was also investigated using scanning electrochemical microscopy (SECM) and scanning tunneling microscopy (STM) and involved transmembrane electrochemistry of erythrocytes superimposed to molecular electrochemistry of heme-containing proteins and heme fragments in the plasma. Voltammetric testing …

Characterizing archaeological bronze corrosion products intersecting electrochemical impedance measurements with voltammetry of immobilized particles

Application of electrochemical impedance measurements to microparticulate deposits of copper corrosion products attached to graphite electrodes in contact with 0.10 M aqueous HClO4 electrolyte is described. The impedance measurements were sensitive to the applied potential and the amount of solid sample and were modeled taking into account the contribution of the uncovered base electrode. Several pairs of circuit elements provide monotonic variations which are able to characterize different corrosion compounds regardless the amount of microparticulate solid on the electrode. Application to a set of archaeological samples from the archaeological Roman site of Gadara (Jordan, 4th century AD) …

Bioelectrochemical monitoring of soluble guanylate cyclase inhibition by the natural β-carboline canthin-6-one

Abstract The inhibition of soluble guanylate cyclase (sGC) by canthin-6-one alkaloid ( L1 ) is presented and the mechanism of deactivation is studied using solution phase and voltammetry of microparticles methodologies. Possible inhibition pathways: oxidation of Fe 2+ to Fe 3+ coupled to reduction of the naphthyridone motif present by the canthin-6-one and coordinating or reacting of L1 with cysteine units of sGC, are balanced.

Electrochemical identification of toxigenic fungal species using solid-state voltammetry strategies.

An electrochemical methodology for the characterization of mycotoxin-producing fungal species from the genera Aspergillus and Fusarium using solid-state voltammetry is described. Upon attachment of fungal colony microsamples to glassy carbon electrodes in contact with aqueous acetate buffer, characteristic voltammetric signals mainly associated to the oxidation of polyphenolic metabolites are recorded. The possibility of fungi-localized electrochemical processes was assessed by means of electron microscopy and field emission scanning electrochemical microscopy coupled to the application of oxidative potential inputs. Using pattern recognition methods, the determined voltammetric profiles we…

Determination of the depth profile distribution of guest species in microporous materials using the voltammetry of immobilized particles methodology: application to lapachol attachment to palygorskite and kaolinite.

A model for determining the in-depth profile distribution of electroactive species hosted in inorganic microporous matrixes using the voltammetry of immobilized particles methodology is described. The method, based on the analysis of cyclic voltammetric data at different potential scan rates, allows us to determine the in-depth profile variation of the concentration of electroactive guest species as well as the evaluation of the (oxidized form)/(reduced form) concentration ratio in cases where two oxidation states of the electroactive species coexist. The application to Maya blue-type materials prepared from lapachol, a naphtoquinonic dye, and palygorskite and kaolinite clays is reported. T…

Screening of pharmacologic adulterant classes in herbal formulations using voltammetry of microparticles.

A solid state electrochemical method for screening different families of adulterant chemicals illegally added to commercial phytotherapuetic formulations is described. The proposed method, based on the voltammetry of microparticles approach, permits a fast and sensitive way to distinguish between anorexics (amfepramone, fenproporex, sibutramine), benzozodiazepinic anxiolytics (clonazepam, flurazepam, alprazolam, midazolam, medazepam, chlordiazepoxide, diazepam), antidepressants (bupropione, fluoxetine, sertraline, paroxetine), diuretics (hydrochlorothiazide, furosemide, chlortalidone, amiloride, spironolactone), and hypoglycemics (glimepiride, chlorpropamide, glibenclamide) based on charact…

Stabilization and detection of hydrophylloquinone as di-O-methyl derivative

Phylloquinone is a redox active naphthoquinone involved in electron transport in plants. The function of this reduced form remains unclear due to its instability, which has precluded detection. Herein, a simple method that permits the stabilization of the reduced form of phylloquinone by di-O-methylation and HPLC detection is described. Fil: Sussmann, Rodrigo A. C.. Universidade de Sao Paulo; Brasil Fil: de Moraes, Marcilio M.. Universidade de Sao Paulo; Brasil Fil: Cebrián Torrejón, Gerardo. Universidad de Valencia; España. Universidade de Sao Paulo; Brasil Fil: Porta, Exequiel Oscar Jesús. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - …

Superior Electrocatalytic Activity of MoS2-Graphene as Superlattice

[EN] Evidence by selected area diffraction patterns shows the successful preparation of large area (cm x cm) MoS2/graphene heterojunctions in coincidence of the MoS2 and graphene hexagons (superlattice). The electrodes of MoS2/graphene in superlattice configuration show improved catalytic activity for H-2 and O-2 evolution with smaller overpotential of +0.34 V for the overall water splitting when compared with analogous MoS2/graphene heterojunction with random stacking.

Solvent-Independent Electrode Potentials of Solids Undergoing Insertion Electrochemical Reactions: Part I. Theory

A formally solvent-independent redox system can be theoretically defined using the Lovric and Scholz modeling of the voltammetry of microparticles for ion-insertion solids. The proposed theory is based on the extra-thermodynamic assumptions that no net charge accumulates at the solid|electrolyte interface and the assumption that the structure of the solid and the ion binding remain unaffected by the solvent. Under voltammetric conditions, the corresponding redox potential can be estimated from voltammetric and chronoamperometric data assuming electrochemical reversibility and diffusive charge transport in the solution and solid phases, also taking into account ion partition (electrolyte/sol…

Electrochemical discrimination of mints: The last Chinese emperors Kuang Hsü and Hsüan T'ung monetary unification.

[EN] An electrochemical methodology for discriminating monetary emissions, a recurrent problem in much archaeological studies, is introduced. The method is based on the record of voltammetric signatures of cuprite and tenorite corrosion products in the patina using a minimally invasive nanosampling following the voltammetry of immobilized particles methodology. A model for the depth variation of voltammetric electrochemical parameters characterizing the composition of the corrosion patinas is presented. This model permits to rationalize electrochemical data and discriminate different monetary emissions. The application of this technique, corroborated by electrochemical impedance spectroscop…

"Sweet Chemistry": a Green Way for Obtaining Selenium Nanoparticles Active against Cancer Cells

We present an environment friendly synthesis of selenium nanoparticles and the study of their cytotoxic activity against uterine sarcoma cancer and fibroblasts cells. Amorphous selenium (a-SeNPs) and trigonal selenium (t-SeNPs) were synthesized using D-fructose as the reducing agent and characterized by high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction analysis (XRD), inductively coupled plasma optical emission spectrometry (ICP OES), dynamic light scattering (DLS) to obtain zeta potential values and cyclic voltammetry (CV). Particularly, a-SeNPs presented high toxicity toward the resistant cancer cell line MES-SA/…

Few-layer Black Phosphorous Catalyzes Radical Additions to Alkenes Faster than Low-valence Metals

Abstract The substitution of catalytic metals by p‐block main elements has a tremendous impact not only in the fundamentals but also in the economic and ecological fingerprint of organic reactions. Here we show that few‐layer black phosphorous (FL‐BP), a recently discovered and now readily available 2D material, catalyzes different radical additions to alkenes with an initial turnover frequency (TOF0) up to two orders of magnitude higher than representative state‐of‐the‐art metal complex catalysts at room temperature. The corresponding electron‐rich BP intercalation compound (BPIC) KP6 shows a nearly twice TOF0 increase with respect to FL‐BP. This increase in catalytic activity respect to t…

Description of Solid-to-Solid Redox Processes Based on the Voltammetry of Immobilized Particles Methodology: A Logistic Approximation

A semiempirical model to describe the voltammetry of nontopotactic solid-to-solid redox processes occurring in the voltammetry of immobilized particles (VIMP) electrochemistry is described. It is applied to the reduction of solid metal compounds to the corresponding metal in contact with suitable electrolytes. The model is based on the assumption that the transferred charge is a logistic function of the applied potential, a situation that applies for reversible redox processes involving strongly adsorbed reactants. The model satisfactorily applies to reproduce linear potential scan curves recorded for graphite electrodes modified with different lead compounds (PbO, PbCl2·2H2O, lead-tin yell…

Phytoelectrochemical analysis ofZanthoxylum chiloperone

Introduction An innovative application of the voltammetry of microparticles methodology to characterize the phytochemical composition of extracts of different parts of Zanthoxylum chiloperone var. angustifolium Engl. is described. Objective Characterize the phytochemical composition of extracts of different parts of plants by electrochemical methodologies. Methods The voltammetry of microparticles methodology was applied to alcoholic extracts from leaves, seeds, fruits, roots and stem bark of Zanthoxylum chiloperone. Results In contact with aqueous phosphate buffer, characteristic cathodic signals of its main natural products (canthin-6-one, 5-methoxycanthin-6-one and trans-avicennol) were …

Homo- and Heterobinuclear Cu2+ and Zn2+ Complexes of Ditopic Aza Scorpiand Ligands as Superoxide Dismutase Mimics

Two polytopic aza-scorpiand-like ligands, 6-[7-(diaminoethyl)-3,7-diazaheptyl]-3,6,9-triaza-1-(2,6-pyridina)cyclodecaphane (L1) and 6-[6′-[3,6,9-triaza-1-(2,6-pyridina)cyclodecaphan-6-yl]-3-azahexyl]-3,6,9-triaza-1-(2,6-pyridina)cyclodecaphane (L2), have been synthesized. The acid–base behavior and Cu2+, Zn2+, and Cu2+/Zn2+ mixed coordination have been analyzed by potentiometry, cyclic voltammetry, and UV–vis spectroscopy. The resolution of the crystal structures of [Cu2L2Cl2](ClO4)2·1.67H2O (1), [Cu2HL2Br2](ClO4)3·1.5H2O (2), and [CuZnL2Cl2](ClO4)2·1.64H2O (3) shows, in agreement with the solution data, the formation of homobinuclear Cu2+/Cu2+ and heterobinuclear Cu2+/Zn2+ complexes. The m…

Electrochemical characterization of mangrove sediments: A proposal of new proxies for organic matter oxidation

Abstract The voltammetric response of microparticulate deposits resulting from solvent evaporation of ethanolic extracts of mangrove sediments in contact with aqueous acetate buffer is hereby described. Dated sediment cores sampled from the Peruvian mangrove system (“Manglares de Tumbes” National Sanctuary) presented voltammetric responses dominated by oxidative signals of organic components that exhibit significant variations depending on the depth. Voltammetric data allowed for the definition of electrochemical indexes representative of the electrochemically oxidable organic matter fraction. These electrochemical indexes were fEAOM (for the total amount of organic matter being electrochem…

CCDC 1873814: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1873813: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1507631: Experimental Crystal Structure Determination

Related Article: Lluís Guijarro, Mario Inclán, Javier Pitarch-Jarque, Antonio Doménech-Carbó, Javier U. Chicote, Sandra Trefler, Enrique García-España, Antonio García-España, Begoña Verdejo|2017|Inorg.Chem.|56|13748|doi:10.1021/acs.inorgchem.7b01756

CCDC 1472832: Experimental Crystal Structure Determination

Related Article: Luis M. López-Martínez, Javier Pitarch-Jarque, Àlvar Martínez-Camarena, Enrique García-España, Roberto Tejero, Hisila Santacruz-Ortega, Rosa-Elena Navarro, Rogerio R. Sotelo-Mundo, Mario Alberto Leyva-Peralta, Antonio Doménech-Carbó, and Begoña Verdejo|2016|Inorg.Chem.|55|7564|doi:10.1021/acs.inorgchem.6b01006

CCDC 1873815: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1873817: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1507632: Experimental Crystal Structure Determination

Related Article: Lluís Guijarro, Mario Inclán, Javier Pitarch-Jarque, Antonio Doménech-Carbó, Javier U. Chicote, Sandra Trefler, Enrique García-España, Antonio García-España, Begoña Verdejo|2017|Inorg.Chem.|56|13748|doi:10.1021/acs.inorgchem.7b01756

CCDC 1873812: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1873819: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1873818: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1873820: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1873816: Experimental Crystal Structure Determination

Related Article: Kristina S. Kisel, Alexei S. Melnikov, Elena V. Grachova, Antti J. Karttunen, Antonio Doménech-Carbó, Kirill Yu. Monakhov, Valentin G. Semenov, Sergey P. Tunik, Igor O. Koshevoy|2019|Inorg.Chem.|58|1988|doi:10.1021/acs.inorgchem.8b02974

CCDC 1507630: Experimental Crystal Structure Determination

Related Article: Lluís Guijarro, Mario Inclán, Javier Pitarch-Jarque, Antonio Doménech-Carbó, Javier U. Chicote, Sandra Trefler, Enrique García-España, Antonio García-España, Begoña Verdejo|2017|Inorg.Chem.|56|13748|doi:10.1021/acs.inorgchem.7b01756