0000000001110424
AUTHOR
Antonio Ribera
Fe3O4@Au@mSiO2 as an enhancing nanoplatform for Rose Bengal photodynamic activity
A novel nanoplatform composed of three types of materials with different functionalities, specifically core-shell Fe3O4@Au nanoparticles encapsulated near the outer surface of mesoporous silica (mSiO2) nanoparticles, has been successfully synthesised and used to enhance the efficiency of a photosensitiser, namely Rose Bengal, in singlet oxygen generation. Fe3O4 is responsible for the unusual location of the Fe3O4@Au nanoparticle, while the plasmonic shell acts as an optical antenna. In addition, the mesoporous silica matrix firmly encapsulates Rose Bengal by chemical bonding inside the pores, thus guaranteeing its photostability, and in turn making the nanosystem biocompatible. Moreover, th…
Photochemical behavior in azobenzene having acidic groups. Preparation of magnetic photoresponsive gels
[EN] The photochemistry of three azobenzenes representing contrasting photochemical behaviors is described in the present work. Thus, Methyl Orange (MO, 4-[[(4-dimethylamino)phenyl]-azo]benzenesulfonic acid sodium salt, hereinafter (1) and 4-hydroxyazobenzene-4'-sulfonic acid (2) undergo in water fast photochemical proton shift, with decays in the microsecond timescale. In contrast to the previous cases, azobenzene-4,4'-dicarboxylic acid (3) undergoes photoisomerization in water. This photochemical behavior allows the preparation of aqueous gels with Aerosil as gelating agent (5% weight) exhibiting high cyclability and photoreversible isomerization of the trans to cis (300 nm irradiation) a…
Interplay between Chemical Composition and Cation Ordering in the Magnetism of Ni/Fe Layered Double Hydroxides
We report the synthesis of a family of ferrimagnetic NiFe layered double hydroxides (LDHs) with a variable Ni(2+)/Fe(3+) in-plane composition of [Ni(1-x)Fe(x)(OH)2](CO3)(x/2)·yH2O (x = 0.20, 0.25, and 0.33) by following a modified homogeneous precipitation. These layered magnets display high crystallinity, homogeneous hexagonal morphologies, and micrometric size that enable their quantitative exfoliation into single layers by sonomechanical treatment of the solids in polar solvents. This was confirmed by dynamic light scattering, UV-vis spectroscopy, high-resolution transmission electron miscroscopy, and atomic force microscopy methodologies to study the resulting steady suspensions. Our ma…
ChemInform Abstract: Hybrid Materials Based on Magnetic Layered Double Hydroxides: A Molecular Perspective
ConspectusDesign of functional hybrids lies at the very core of synthetic chemistry as it has enabled the development of an unlimited number of solids displaying unprecedented or even improved properties built upon the association at the molecular level of quite disparate components by chemical design. Multifunctional hybrids are a particularly appealing case among hybrid organic/inorganic materials. Here, chemical knowledge is used to deploy molecular components bearing different functionalities within a single solid so that these properties can coexist or event interact leading to unprecedented phenomena. From a molecular perspective, this can be done either by controlled assembly of orga…
Magnetic Properties of Ni II Cr III Layered Double Hydroxide Materials
This paper describes the isolation of four layered double hydroxide (LDH) compounds having the general formula[NiII3–xCrIIIx(OH)6](CO3)x/2·yH2O [x = 0.57 (1), 0.69 (2), 0.81 (3) and 0.93 (4)] by using homogeneous precipitation methods and varying the metal ratio in the synthetic solutions. All the reported compounds have carbonate anions in the interlamellar space. This fact forces the interlayer distances to remain unchanged in all the cases, thus providing an ideal system in which the changes observed in magnetic properties can be correlated with metal composition along the hydroxide layers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Confined growth of cyanide-based magnets in two dimensions
Herein we report the first hybrid magnetic material resulting from the intercalation of a cyanide-based molecular magnet into a solid-state layered host. More specifically, the use of a diamagnetic cationic Zn(II)-Al(lII) layered double hydroxide host allows for the formation of an anionic two-dimensional ferromagnetic Ni(II)-Cr(III) Prussian Blue analogue, from the templated assembly of its ionic molecular components in the confined interlamellar space offered by the inorganic host.
Preconcentration of emerging contaminants in environmental water samples by using silica supported Fe3O4 magnetic nanoparticles for improving mass detection in capillary liquid chromatography
A magnetic material based on Fe(3)O(4) magnetic nanoparticles incorporated in a silica matrix by using a sol-gel procedure has been used to extract and preconcentrate emerging contaminants such as acetylsalicylic acid, acetaminophen, diclofenac and ibuprofen from environmental water samples prior to the analysis with Capillary LC-MS. The use of the proposed silica supported Fe(3)O(4) magnetic nanoparticles enables surfactant free extracts for the analysis with MS detection without interferences in the ionisation step. Under the optimum conditions, we demonstrated the reusability of the magnetic sorbent material during 20 uses without loss in the extraction efficiency. In addition, no cleanu…
Coexistence of superconductivity and magnetism by chemical design.
Although the coexistence of superconductivity and ferromagnetism in one compound is rare, some examples of such materials are known to exist. Methods to physically prepare hybrid structures with both competing phases are also known, which rely on the nanofabrication of alternating conducting layers. Chemical methods of building up hybrid materials with organic molecules (superconducting layers) and metal complexes (magnetic layers) have provided examples of superconductivity with some magnetic properties, but not fully ordered. Now, we report a chemical design strategy that uses the self assembly in solution of macromolecular nanosheet building blocks to engineer the coexistence of supercon…
Intercalation of cobalt(II)-tetraphenylporphine tetrasulfonate complex in magnetic NiFe-layered double hydroxide
Abstract Hybrid magnetic multilayers have been synthesized by means of intercalation of [5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato]cobalt(II) (CoTPPS) complex in the interlayer space of a Ni II Fe III layered double hydroxide (LDH), through anion-exchange reaction. A sebacate ( − OOC–(CH 2 ) 8 –COO − ) intercalated NiFe-LDH have been used as precursor, facilitating the anion exchange reaction, thus permitting the inclusion of a paramagnetic macrocycle inside the ferrimagnetic NiFe-LDH layers. The material has been characterized by XRD, FT-IR, SEM, SQUID and ESR. The T c for the hybrid NiFe–CoTPPS, ca. 11–12 K, is very close to that shown by the precursor, despite that the intercala…
Self-Assembly of 1D/2D Hybrid Nanostructures Consisting of a Cd(II) Coordination Polymer and NiAl-Layered Double Hydroxides
The preparation and characterization of a novel hybrid material based on the combination of a 2D-layered double hydroxide (LDH) nanosheets and a 1D-coordination polymer (1D-CP) has been achieved through a simple mixture of suspensions of both building blocks via an exfoliation/restacking approach. The hybrid material has been thoroughly characterized demonstrating that the 1D-CP moieties are intercalated as well as adsorbed on the surface of the LDH, giving rise to a layered assembly with the coexistence of the functionalities of their initial constituents. This hybrid represents the first example of the assembly of 1D/2D nanomaterials combining LDH with CP and opens the door for a plethora…
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.
Hybrid Materials Based on Magnetic Layered Double Hydroxides: A Molecular Perspective
Design of functional hybrids lies at the very core of synthetic chemistry as it has enabled the development of an unlimited number of solids displaying unprecedented or even improved properties built upon the association at the molecular level of quite disparate components by chemical design. Multifunctional hybrids are a particularly appealing case among hybrid organic/inorganic materials. Here, chemical knowledge is used to deploy molecular components bearing different functionalities within a single solid so that these properties can coexist or event interact leading to unprecedented phenomena. From a molecular perspective, this can be done either by controlled assembly of organic/inorga…
Metal-functionalized covalent organic frameworks as precursors of supercapacitive porous N-doped graphene
Covalent Organic Frameworks (COFs) based on polyimine with several metal ions (FeIII, CoII and NiII) adsorbed into their cavities have shown the ability to generate N-doped porous graphene from their pyrolysis under controlled conditions. These highly corrugated and porous graphene sheets exhibit high values of specific capacitance, which make them useful as electrode materials for supercapacitors.
The catalytic reduction of nitrobenzene at the [MoVIO2(O2CC(S)(C6H5)2)2]2? complex intercalated in a Zn(II)-Al(III) layered double hydroxide host: A kinetic model for the molybdenum-pterin binding site in nitrate reductase
The heterogeneous reduction of nitrobenzene by thiophenol catalyzed by the dianionic bis(2-sulfanyl-2,2-diphenylethanoxycarbonyl) dioxomolybdate(VI) complex, [MoVIO2(O2CC(S)(C6H5)2)2]2−, intercalated into a Zn(II)–Al(III) layered double hydroxide host [Zn3−xAlx(OH)6]x+, has been investigated under anaerobic conditions. Aniline was found to be the only product formed through a reaction consuming six moles of thiophenol for each mol of aniline produced. The kinetics of the system have been analyzed in detail. In excess of thiophenol, all reactions follow first-order kinetics (ln([PhNO2]/[PhNO2]0) = −kappt) with the apparent rate constant kapp being a complex function of both initial nitrobenz…
Stimuli-responsive hybrid materials: breathing in magnetic layered double hydroxides induced by a thermoresponsive molecule
[EN] A hybrid magnetic multilayer material of micrometric size, with highly crystalline hexagonal crystals consisting of CoAl-LDH ferromagnetic layers intercalated with thermoresponsive 4-(4-anilinophenylazo)benzenesulfonate (AO5) molecules diluted (ratio 9 : 1) with a flexible sodium dodecylsulphate (SDS) surfactant has been obtained. The resulting material exhibits thermochromism attributable to the isomerization between the azo (prevalent at room temperature) and the hydrazone (favoured at higher temperatures) tautomers, leading to a thermomechanical response. In fact, these crystals exhibited thermally induced motion triggering remarkable changes in the crystal morphology and volume. In…
Hybrid Magnetic Multilayers by Intercalation of Cu(II) Phthalocyanine in LDH Hosts
The intrinsic flexibility of layered double hydroxides (LDHs) has been here exploited to design hybrid multilayered materials by intercalation of the copper phthalocyaninetetrasulfonate (CuPcTs) complex in the interlamellar space offered by these layered hosts through a simple anion-exchange procedure. Taking advantage of their chemical versatility, two different LDHs, the diamagnetic ZnAl and the ferromagnetic NiAl, have been synthesized and characterized to explore the differences in the magnetic properties of the hybrids introduced by the intercalation of the paramagnetic complex.
Synthesis, characterization and magnetism of monodispersed water soluble palladium nanoparticles
Water soluble, monodispersed Pd nanoparticles with a narrow particle size distribution have been successfully synthesized by controlled reduction of [PdCl4]2−. The resulting aqueous colloids are stable over extended periods of time and can be prepared at high nanoparticle loading (20 g/L of Pd) with no agglomeration. The size of the nanoparticles can be reduced from the nanometer (ca. 3.5 nm) to the sub-nanometer size range (ca. 0.9 nm). Detailed magnetic characterization indicated that the larger, 3.5 nm nanoparticles show ferromagnetic properties at room temperature, while the sub-nanometric ones lose this magnetic behavior.
Solid-state electrochemistry of LDH-supported polyaniline hybrid inorganic–organic material
Abstract The solid-state electrochemistry of a Zn–Al layered double hydroxide-supported polyaniline material (LDH-PANI) in contact with aqueous electrolytes is described. Interconversion processes between different forms (emeraldine, protoemeraldine, leucoemeraldine, nigraniline and pernigraniline) of the LDH-supported polyaniline units are involved in redox processes. This material exhibits significant variations of impedance upon application of different conditioning potentials, acting as an electrochemical frequency filter. Using Fe (CN) 6 4 - as redox probe, LDH-PANI can be used as a chemical–electrochemical information processing system equivalent to different combinational logic circu…
Intercalation of [M(ox)3]3− (M=Cr, Rh) complexes into NiIIFeIII-LDH
Abstract Layered Double Hydroxides (LDH) containing paramagnetic NiII and FeIII ions in the hydroxide layers and chromium or rhodium oxalate complexes at the interlayer space were prepared by ion exchange from a NiFe-LDH precursor with sebacate anions between the hydroxide layers. The precursor was synthesized by coprecipitation at controlled pH in order to avoid the formation of solid phases different from LDH. Magnetic studies demonstrated that both LDHs, NiFe–Cr(ox)3 and NiFe–Rh(ox)3, exhibited a behaviour similar to the precursor. Nevertheless, the substitution of intercalated sebacate anions with oxalate complexes compresses the LDH basal spacing, increasing the intensity of dipolar in…
The synthesis of a hybrid graphene–nickel/manganese mixed oxide and its performance in lithium-ion batteries
Abstract Mixing of aqueous suspensions of delaminated NiMn layered double hydroxide (LDH) and graphene oxide leads to the instantaneous precipitation of a hybrid material that after calcination under inert atmosphere at 450 °C leads to Ni6MnO8 nanoparticles deposited on larger reconstituted graphene sheets. This material exhibits electrical conductivity similar to graphite, superparamagnetism and can be used as an anode for Li-ion batteries. A maximum capacity value of 1030 mA h g−1 was found during the first discharge, and capacity values higher than 400 mA h g−1 were still achieved after 10 cycles. The methodology used here should allow the preparation of a large variety of hybrid graphen…
Hybrid magnetic materials formed by ferritin intercalated into a layered double hydroxide
A hybrid magnetic material formed by ferritin intercalated into a layered double hydroxide (LDH) of Mg and Al (Mg/Al molar ratio 2) is prepared and characterized through powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, electron probe microanalysis (EPMA) and high resolution transmission electron microscopy (HRTEM). One observes an enhancement in the thermal stability of the ferritin molecules when they are inserted in the layered material. Magnetic measurements of the hybrid material exhibit the typical superparamagnetic behaviour of the ferritin molecule. On the other hand, the intercalation of ferritin into the LDH guarante…
Graphene as a carbon source effects the nanometallurgy of nickel in Ni,Mn layered double hydroxide-graphene oxide composites.
[EN] Thermal treatment of the hybrid material formed by the spontaneous precipitation of graphene oxide and Ni,Mn layered double hydroxide leads to the segregation of nickel metal nanoparticles (Ni NPs) and the decomposition of graphene to CO2. Increasing the temperature increases the Ni NP size and results in the complete disappearance of graphene.
Photo-switching in a hybrid material made of magnetic layered double hydroxides intercalated with azobenzene molecules.
Financial support from the EU (Projects HINTS FP7-263104-2 and SpinMol Advanced Grant ERC-2009-AdG-20090325), the Spanish Ministerio de Economia y Competitividad (Projects with FEDER cofinancing MAT 2009-14528-C02-01, MAT2011-22785, MAT2012-38567-C02-01, CTQ-2011-26507, Consolider-Ingenio in Molecular Nanoscience CSD2007-00010, Consolider-Ingenio 2010-Multicat CSD2009-00050, and Severo Ochoa Program SEV-2012-0267), Generalitat Valenciana (PROMETEO and ISIC-Nano programs), and VLC/Campus Microcluster "Functional Nanomaterials and Nanodevices" is gratefully acknowledged. C. M. G. thanks the Spanish MINECO for a Ramon y Cajal Fellowship (RYC-2012-10894). We also acknowledge P. Atienzar and J. …
NOx selective catalytic reduction at high temperatures with mixed oxides derived from layered double hydroxides
[EN] Mixed oxides derived from layered double hydroxides (LDHs) have been investigated as potential catalysts for the NOx removal at high temperatures. The best results were obtained with Co–Al mixed oxides derived from LDHs that are active at 750 ◦C in the presence of oxygen and water. These catalysts could reduce or/and decompose the NOx formed in the dense phase of the FCC regenerator, being deactivated at oxygen concentrations higher than 1.5%. Nevertheless this deactivation is not permanent and they would be regenerated after reduction with hydrogen at 530 ◦C. The influence of the layered double hydroxides (LDHs) preparation method on the catalyst activity was studied, observing that t…
ChemInform Abstract: Magnetic Properties of NiIICrIIILayered Double Hydroxide Materials.
This paper describes the isolation of four layered double hydroxide (LDH) compounds having the general formula[NiII3–xCrIIIx(OH)6](CO3)x/2·yH2O [x = 0.57 (1), 0.69 (2), 0.81 (3) and 0.93 (4)] by using homogeneous precipitation methods and varying the metal ratio in the synthetic solutions. All the reported compounds have carbonate anions in the interlamellar space. This fact forces the interlayer distances to remain unchanged in all the cases, thus providing an ideal system in which the changes observed in magnetic properties can be correlated with metal composition along the hydroxide layers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Illustrating the processability of magnetic layered double hydroxides: layer-by-layer assembly of magnetic ultrathin films.
We report the preparation of single-layer layered double hydroxide (LDH) two-dimensional (2D) nanosheets by exfoliation of highly crystalline NiAl-NO3 LDH. Next, these unilamellar moieties have been incorporated layer-by-layer (LbL) into a poly(sodium 4-styrenesulfonate)/LDH nanosheet multilayer ultrathin film (UTF). Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible light (UV-vis), and X-ray diffraction (XRD) profiles have been used to follow the uniform growth of the UTF. The use of a magnetic LDH as the cationic component of the multilayered architecture enables study of the resulting magnetic properties of the UTFs. Our magnetic data show the appearance of spontaneous …
Electrochemistry of hydrotalcite-supported bis(2-mercapto-2,2-diphenyl-ethanoate) dioxomolybdate complexes.
The redox properties of the hydrotalcite-intercalated bis(2-mercapto-2,2-diphenyl-ethanoate) dioxomolybdate(VI) complex are investigated by cyclic voltammetry by using modified carbon paste electrodes and clay-modified electrodes. The electrochemical data provide evidence that boundary-associated species involving the VI, V and IV oxidation states of molybdenum are responsible for the electroactivity.
Dalton communication. Crystal structure and oxo-transfer properties of [NH4]2[WVIO2{O2CC(S)Ph2}2]
The complex [NH4]2[WVIO2{O2CC(S)Ph2}2] is the first example of a non-dithiolene tungsten complex capable of oxidising benzoin to benzil in methanol; the reduced complex product formed, presumably a monomeric WVIO species, was reoxidised with nitrate ions, regenerating the starting WVIO2 complex which then acts as a true homogeneous catalyst.
Magnetic Nanocomposites Formed by FeNi3 Nanoparticles Embedded in Graphene. Application as Supercapacitors
A general family of magnetic nanocomposites formed by FeNi3 ferromagnetic nanoparticles (NPs) embedded in a graphitized carbon matrix is reported. The soft chemical approach used relies on the catalytic effect of the NPs resulting from the thermal decomposition of the layered double hydroxide precursor, which acts as a multilayered nanoreactor enabling the formation of a range of carbon nanoforms (CNFs). This is followed by acid treatment of the as-prepared nanocomposites to isolate the different CNFs formed. These range from carbon nano-onions to graphene depending on the temperature of the thermal decomposition. This synthetic process paves the way for the rational design of metal–carbon …
Insertion of Magnetic Bimetallic Oxalate Complexes into Layered Double Hydroxides
Bimetallic oxalate complexes have been successfully inserted into layered double hydroxides as ferromagnetic oxalate-bridged oligomers. Different preparation methods afford different sizes and compositions for the oligomers. In all cases, no magnetic ordering has been observed above 2 K.
Intercalation of two-dimensional oxalate-bridged molecule-based magnets into layered double hydroxide hosts
Here we report the intercalation of a MnII–CrIII oxalate-bridged extended network into the interlamellar space offered by a ZnII–AlIII LDH host. This material exhibits ferrimagnetic ordering below 3 K from dominant antiferromagnetic interactions between metallic centres through the oxalate linker. Our result opens the door for the design of a completely new sort of hybrid magnetic multilayers from molecule-based magnets and layered inorganic flexible hosts, where the intrinsic properties of both sub-layers can be combined.
A chemical and electrochemical multivalent memory made from FeNi3-graphene nanocomposites
FeNi3-graphene nanocomposites present in acetonitrile solutions a redox couple with an electrochemical hysteresis of 2.4 V between the oxidation and the reduction maxima. In view of the high energy required for the reverse transitions, they are here proposed as chemical multilevel memories: permanent, after drying, or erasable in electrolytes, respectively. Keywords: FeNi3-graphene nanocomposites, Voltammetry, Coulovoltammetry, Redox couple, Redox hysteresis
Hexagonal nanosheets from the exfoliation of Ni2+-Fe3+ LDHs: a route towards layered multifunctional materials
Here we report the synthesis of a crystalline micrometric-sized hexagonal-shaped Ni2+-Fe3+ LDH by following a modified homogeneous precipitation method. The exfoliation of the material in formamide leads to stable suspensions of hexagonal nanometric sheets, which have been extensively characterized. Our data confirm that the intrinsic properties of the bulk material are retained by these segregated nanosheets, thus opening the door for their use in the development of layered multifunctional materials.
Study of the influence of dynamics variables on the growth of silica nanoparticles
In this work 29Si nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared spectroscopy (FTIR) were used to analyze in situ the formation process of silica nanoparticles from ba...
Gold-nanoparticles ingestion disrupts reproduction and development in the German cockroach.
The present work shows the effects of gold nanoparticles (AuNPs) orally administered on reproduction and development of the insect Blattella germanica. Newly emerged females were provided with food containing AuNPs (87.44μg/g) of a size between 15 and 30nm (mean 21.8nm), and were allowed to mate with males. Food ingestion, mortality, reproductive parameters (time to ootheca formation and eclosion, ootheca viability and fertility) as well as postembryonic developmental parameters of the first ootheca (nymphal survival and life span) were recorded throughout the experiment. Gold from AuNPs was accumulated by adults of B. germanica with a bioaccumulation factor of 0.1. Ingestion of AuNPs did n…
Incorporation of Pd nanoparticles in mesostructured silica
Monodisperse Pd nanoparticles were prepared by controlled reduction in organic phase and subsequent transfer to aqueous phase. A systematic study was carried out to finely tune nanoparticle size and optimize particle size distribution. The use of 4-dimethylaminopyridine as a transfer agent allowed for the easy and quantitative extraction of the Pd to the aqueous phase. The quaternary amine-functionalized metal nanoparticles were then used as metallic micelle replicas to grow silica around them. This novel and facile metal incorporation method provided an excellent dispersion and homogeneity of Pd nanoparticles on silica supports. In addition, cationic surfactants, such as cetyltrimethylammo…
Increased photocatalytic activity and selectivity towards methane of trimetallic NiTiAl-LDH
Layered double hydroxides is a rising family of materials with interesting photocatalytic properties that are starting to be employed on the CO photoreduction to useful chemicals. However, the selectivity control towards high energy value products, such as methane or methanol, is one of the main issues of this process due to the easier formation of CO, which requires fewer electrons to be transferred, and the competition of hydrogen evolution reaction. In this work, a new LDH material containing Ni, Ti and Al within the structure was synthesised with the purpose of increasing the selectivity towards methane production. The material was tested under solar simulator conditions, yielding a met…
Layered double hydroxide (LDH)–organic hybrids as precursors for low-temperature chemical synthesis of carbon nanoforms
A low-temperature route for the chemical synthesis of diverse carbon nanoforms, including nano-onions and multi-walled nanotubes, is described. The method involves thermal decomposition of a sebacate-intercalated NiFe LDH at 400 °C and benefits from the catalytic activity of FeNi3 nanoparticles generated in situ.
A kinetic model for the oxidation of benzenethiol catalyzed by the [MoVIO2(O2CC(S)(C6H5)2)2]2− complex intercalated in a Zn(II)–Al(III) layered double hydroxide host
Abstract The heterogeneous oxidation of benzenethiol catalyzed by the dianionic bis(2-sulfanyl-2,2-diphenylethanoxycarbonyl) dioxomolybdate (VI) complex intercalated into a Zn(II)–Al(III) layered double hydroxide (LDH) host have been investigated under aerobic conditions. The kinetics of the system has been analysed in detail. In ethanol, the benzenethiol is cleanly oxidized to diphenyl disulfide in the acidic media provided by the protonic resin Amberlite IR-120(H). The reaction is second-order in benzenethiol, and the apparent rate coefficient has been found to be proportional to the catalyst weight and inversely proportional to the initial concentration of the substrate. A catalytic cycl…
Evaluation of Superparamagnetic Silica Nanoparticles for Extraction of Triazines in Magnetic in-Tube Solid Phase Microextraction Coupled to Capillary Liquid Chromatography
The use of magnetic nanomaterials for analytical applications has increased in the recent years. In particular, magnetic nanomaterials have shown great potential as adsorbent phase in several extraction procedures due to the significant advantages over the conventional methods. In the present work, the influence of magnetic forces over the extraction efficiency of triazines using superparamagnetic silica nanoparticles (NPs) in magnetic in tube solid phase microextraction (Magnetic-IT-SPME) coupled to CapLC has been evaluated. Atrazine, terbutylazine and simazine has been selected as target analytes. The superparamagnetic silica nanomaterial (SiO2-Fe3O4) deposited onto the surface of a capil…
The synthesis of a hybrid graphene-nickel/manganese mixed oxide and its performance in lithium-ion batteries
[EN] Mixing of aqueous suspensions of delaminated NiMn layered double hydroxide (LDH) and graphene oxide leads to the instantaneous precipitation of a hybrid material that after calcination under inert atmosphere at 450 degrees C leads to Ni6MnO8 nanoparticles deposited on larger reconstituted graphene sheets. This material exhibits electrical conductivity similar to graphite, superparamagnetism and can be used as an anode for Li-ion batteries. A maximum capacity value of 1030 mAh g(-1) was found during the first discharge, and capacity values higher than 400 mAh g(-1) were still achieved after 10 cycles. The methodology used here should allow the preparation of a large variety of hybrid gr…
Magnetic In-Tube Solid Phase Microextraction
We report a new in-tube solid phase microextraction approach named magnetic in-tube solid phase microextraction, magnetic-IT-SPME. Magnetic-IT-SPME has been developed, taking advantage of magnetic microfluidic principles with the aim to improve extraction efficiency of IT-SPME systems. First, a magnetic hybrid material formed by Fe(3)O(4) nanoparticles supported on SiO(2) was synthesized and immobilized in the surface of a bared fused silica capillary column to obtain a magnetic adsorbent extraction phase. The capillary column was placed inside a magnetic coil that allowed the application of a variable magnetic field. Acetylsalicylic acid, acetaminophen, atenolol, diclofenac, and ibuprofen …