Search results for "Scanning electrochemical microscopy"
showing 10 items of 15 documents
Electrochemical identification of toxigenic fungal species using solid-state voltammetry strategies.
2018
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…
Transmembrane electrochemistry of erythrocytes: Direct electrochemical test for detecting hemolysis in whole blood
2016
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 …
Voltammetry of microparticles, scanning electrochemical microscopy and scanning tunneling microscopy applied to the study of dsDNA binding and damage…
2014
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…
dsDNA, ssDNA, G-quadruplex DNA, and nucleosomal DNA electrochemical screening using canthin-6-one alkaloid-modified electrodes
2014
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…
Redox tuning and species distribution in Maya Blue-type materials: a reassessment.
2013
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…
Scanning electrochemical microscopy as a probe of Ag+ binding kinetics at Langmuir phospholipid monolayers
2005
A new method has been developed for measuring local adsorption rates of metal ions at interfaces based on scanning electrochemical microscopy (SECM). The technique is illustrated with the example of Ag+ binding at Langmuir phospholipid monolayers formed at the water/air interface. Specifically, an inverted 25 microm diameter silver disc ultramicroelectrode (UME) was positioned in the subphase of a Langmuir trough, close to a dipalmitoyl phosphatidic acid (DPPA) monolayer, and used to generate Ag+ via Ag electro-oxidation. The method involved measuring the transient current-time response at the UME when the electrode was switched to a potential to electrogenerate Ag+. Since the Ag+/Ag couple…
Detection of archaeological forgeries of Iberian lead plates using nanoelectrochemical techniques. The lot of fake plates from Bugarra (Spain)
2014
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…
Electrogeneration of Diiodoaurate in Dimethylsulfoxide on Gold Substrate and Localized Patterning
2016
International audience; A localized etching of gold surface by scanning electrochemical microscope technique is presented where a dimethylsulfoxide-based electrolyte charged with iodine is used. The electrogenerated triiodide ion at the platinum ultramicroelectrode tip (feedback mode) acts as an oxidant for gold surface. The effects of electrode diameter and the bias time have been investigated. The approach curve method was used to hold the electrode tip close to the gold surface. A scanning electron microscope is used to observe the etched gold surfaces where disk-shaped dots are generated. The diameter of these holes depends directly on the Pt electrode diameter and the bias time.
Passive Behavior and Passivity Breakdown of AISI 304 in LiBr Solutions through Scanning Electrochemical Microscopy
2014
The passive behavior and passivity breakdown of AISI 304 stainless steel in LiBr solutions has been investigated by means of scanning electrochemical microscopy (SECM). The sample generation - tip collection (SG-TC) mode was used to operate the SECM and the tip potential was biased to detect the electroactive species. The evolution of the current at the ultramicroelectrode tip with the applied potential within the passive range was followed at different LiBr concentrations. Results show that the absolute value of the current at the tip increases with the applied potential. Additionally, SECM was also used to detect stable pits formed on the stainless steel surface in a 0.2 M LiBr solution. …
Screening and mapping of pigments in paintings using scanning electrochemical microscopy (SECM)
2015
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.