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

Abstract

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.

Methyl, Ethyl, Propyl, Butyl: Futile But Not for Water, as the Correlation of Structure and Thermodynamic Signature Shows in a Congeneric Series of Thermolysin Inhibitors

“…50–52. Consistently with this literature and previously reported SECM data for copper‐containing materials 43, 53, metal deposits grow on the vicinity of the parent grains of the mineral, confirming the mainly topotactic local deposition of copper and lead metal during electrochemical turnovers for samples containing mixtures of copper and lead corrosion products.…”

“…Local analysis of selected samples was performed by SECM using a sequential application of different potentials to the substrate. Here, application to the tip of a potential of −0.45 V promotes the electrochemical reduction of dissolved oxygen which will act as a redox probe 43. Figure 9 shows the SECM topographic images of sample 8–2 in contact with air‐saturated 0.10 M aqueous phosphate buffer at pH 7.0 when the substrate electrode is held at a) 0.00, b) −0.15, c) −0.70 V and again d) 0.00 V. The first image (Fig.…”

“…The powdered reference materials and samples were abrasively attached to paraffin‐impregnated graphite bars (Staedtler HB, 68 % wt graphite) following the conventional VIMP protocols 16, 17. SECM experiments were performed in air‐saturated 0.10 M aqueous phosphate buffer at pH 7.0 in order to use dissolved oxygen as a redox probe 43. The bipotentiostat mode was used upon application of fixed potentials to the tip ( E T ) and the electrode substrate ( E S ).…”

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

“…The electrochemical processes involve mainly solid state reactions, (as confirmed by the persistence of the voltammetric response when the time of contact of the deposit with the electrolyte is prolonged) where electron ingress/issue is coupled, by reasons of charge conservation, to the entrance/issue of protons on/from the solid lattice, in agreement with extensive literature on the VIMP of organic compounds. 3b), attributable to the contraction/expansion of the crystals associated to the changes in composition, as already described for the case of flavonoids, 24,47 consistently with the proton-assisted solid state nature of the involved electrochemical processes. [40][41][42][43][44] The solid state nature of the involved electrochemical processes was assessed by SECM.…”

Electrochemical characterization of biodeterioration of paint films containing cadmium yellow pigment

“…Cadmium yellow (CdS) is a modern pigment that displays a widely studied electrochemistry in solid state [31][32][33]. Cadmium yellow was selected as a pigment probe in this study due to its good electrochemical response and its low absorption and conditions were similar to those previously described [41,42].…”