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 archaeological metallic object are presented. (C) 2016 Elsevier B.V. All rights reserved.Research was conducted within the "Grupo de analisis cientifico de bienes culturales y patrimoniales y estudios de ciencia de la conservacion" Microcluster of the University of Valencia Excellence Campus. Financial support is gratefully acknowledged from the MINECO Projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P which are also supported with ERDF funds. The authors would like to thank to Gonzalo Girones Sarrio manager of GongDisseny Co. by the technical support for building the site structure and the structure of the database, Archbishop of Valencia, Dr. Ignacio Bosch Reig and Dr. Pilar Roig Picazo directors of the intervention project in the Basilica de la Virgen de los Desamparados de Valencia, the conservator Estrella Arcos Von Haartman (Quibla Restaura Company) and City Council Town of Malaga, the Museum of Archaeology of Xativa, its director Angel Velasco and the conservators Isabel Martinez Lazaro and Betlem Martinez for facilitating access to samples as well as Manuel Planes Insausti and Dr Jose Luis Moya Lopez technical supervisors of the Electron Microscopy Service of the Universitat Politecnica de Valencia where were carried out SEM-EDX analyses.Domenech-Carbo, A.; Domenech Carbo, MT.; Valle-Algarra, FM.; Gimeno-Adelantado, J.; Osete Cortina, L.; Bosch-Reig, F. (2016). On-line database of voltammetric data of immobilized particles for identifying pigments and minerals in archaeometry, conservation and restoration (ELCHER database). Analytica Chimica Acta. 927:1-12. https://doi.org/10.1016/j.aca.2016.04.052S11292

Electrocatalysis of neurotransmitter catecholamines by 2,4,6-triphenylpyrylium ion immobilized inside zeolite Y supercages

2,4,6-Triphenylpyrylium ions entrapped inside the supercages of Y zeolite exert a remarkable catalytic effect toward the electrochemical oxidation of dopamine and norepinephrine (neurotrasmitter catecholamines) in neutral aqueous media.Domenech Carbo, Antonio, [email protected]

Electrochemical discrimination of mints: The last Chinese emperors Kuang Hsu and Hsuan 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 spectroscopy (EIS) and focusing ion beam-field emission scanning electron microscopy (FIB-FESEM-EDX), to a series of 10 cash copper coins produced around the Kuang Hsu and Hsuan Tung last Chinese emperors permits to discern different provincial mints and reveals that the monetary unification developed in this period was not uniform.Financial support from the Spanish MINECO Projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P which are also supported with ERDF funds. The Universita degli Studi di roma "La Sapienza" has granted a six-months research-scholarship (d.r.n. 965/2016 prot.n.0022041 del 31/03/2016) to the graduated Elena Montagna. The authors also wish to thank Dr. Jose Luis Moya Lopez and Mr. Manuel Planes Insausti (Microscopy Service of the Universitat Politecnica de Valencia) for technical supportDomenech-Carbo, A.; Domenech Carbo, MT.; Montagna, E.; Álvarez-Romero, C.; Lee, Y. (2017). Electrochemical discrimination of mints: The last Chinese emperors Kuang Hsu and Hsuan T'ung monetary unification. Talanta. 169:50-56. https://doi.org/10.1016/j.talanta.2017.03.025S505616

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

[EN] 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) permitted to establish a grouping of such samples suggesting different provenances/manufacturing techniques.Financial support from the MINECO ProjectsCTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P which are also supported with ERDF funds and Grants ES-2012-052716 and EEBB-I-16-11558 is gratefully acknowledgedRedondo-Marugan, J.; Piquero-Cilla, J.; Domenech Carbo, MT.; Ramírez-Barat, B.; Al Sekhaneh, W.; Capelo, S.; Doménech Carbó, A. (2017). Characterizing archaeological bronze corrosion products intersecting electrochemical impedance measurements with voltammetry of immobilized particles. Electrochimica Acta. 246:269-279. https://doi.org/10.1016/j.electacta.2017.05.190S26927924

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 insertion, reduction with cation insertion and reduction with anion issue processes, whose thermochemical aspects, involving separate ion and electron transport contributions, are discussed.Financial support from the Project CTQ2017-85317-C2-1-P (Ministerio de Economia, Industria y Competitividad (MINECO), Fondo Europeo de Desarrollo Regional (ERDF) and Agencia Estatal de Investigacion (AEI)), is gratefully acknowledged.Doménech-Carbó, A.; Dias, D.; Domenech Carbo, MT. (2020). Cation and anion electrochemically assisted solid-state transformations of malachite green. Physical Chemistry Chemical Physics. 22(3):1502-1510. https://doi.org/10.1039/c9cp05835dS1502151022

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 layer. The voltammetric study of the metallographic samples of the bronze objects shows correlation with the age of the objects, respectively the period of their deposition. We discuss also (potential) influence of different factors on the VIMP and OCP measurements, such as deposition context (soil, water), chemical composition of the copper alloys, and microstructural features (ascast, annealed, work-hardened), and how to overcome these issues.Project CTQ2017-85317-C2-1-P, supported with Ministerio de Economia, Industria y Competitividad (MINECO), Fondo Europeo de Desarrollo Regional (ERDF) and Agencia Estatal de Investigacion (AEI), is gratefully acknowledged.Doménech-Carbó, A.; Mödlinger, M.; Domenech Carbo, MT. (2021). Multiple-scan voltammetry and OCP: Archaeometric tools for dating archaeological bronzes. Journal of Electroanalytical Chemistry. 893:1-9. https://doi.org/10.1016/j.jelechem.2021.115336S1989

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.Financial support from the Spanish MINECO Projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P which are also supported with ERDF funds.Doménech Carbó, A.; Domenech Carbo, MT. (2018). Electroanalytical techniques in archaeological and art conservation. Pure and Applied Chemistry. 90(3):447-461. https://doi.org/10.1515/pac-2017-0508S44746190

Electrochemical assessment of pigments-binding medium interactions in oil paint deterioration: a case study on indigo and Prussian blue

Abstract The degradation of laboratory oil paint film specimens containing indigo and Prussian blue pigments and pictorial samples from the Sant Francesc de Paula painting exhibited in the Tomàs Balvey Arxiu Museum (Cardedeu (Catalonia), Spain) has been studied by voltammetry of immobilized particles. This technique, combined with light microscopy, scanning electron microscopy-energy dispersive X-ray analysis, nanoindentation-atomic force microscopy, attenuated total reflectance-Fourier-transform infrared spectroscopy and gas chromatography–mass spectroscopy techniques permits the proposal of a dual scheme for the degradation of the pigments when naturally aged and submitted to accelerated UVA aging. Under conditions of moderate temperature, humidity and natural illumination, and low gradients of these parameters, Prussian blue acts as a radical scavenger moderating the production of reactive oxygen species produced in the oil binding medium by the action of ultraviolet radiation, resulting in the formation, in the solid state, of the solid-solution, {KFeIII[FeII(CN)6]} x {FeIII[FeIII(CN)6]}1–x , known as Berlin green, which then promotes the formation of indigo adducts with radicals. In several localized areas of the Sant Francesc de Paula paint showing strong degradation, Prussian blue acts as a promoter of the indigo oxidation to isatin, thus resulting in a considerable chromatic shift

Funerary colors in Pre-classical Maya culture: the red pigment in the 19th tomb of Rio Azul (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, electrochemical and chromatographic techniques. The results have enabled the identification of the inorganic and organic materials composing these pigmenting materials found in a ceramic posthumous offering dish and further discussion mainly has been focused on the geological source of the inorganic materials and the possible origin of the organic matter accompanying these two pigmenting materials

Electrochemical analysis of gold embroidery threads from archeological textiles

[EN] A methodology for characterizing archeological gold embroidery threads based on two analytical techniques is described: Field emission scanning electron microscopy (FESEM-EDX) and voltammetry of immobilized microparticle (VIMP) methodologies. After the analysis of the chemical composition of the metallic foil, we analyze specific voltammetric features associated with the oxidation of gold in contact with aqueous H2SO4 and HCl electrolytes. Cyclic and square wave voltammetries (VMP) have been used to get information about the elemental composition and the corrosion products of the samples. AFM, FESEM-EDX, and FESEM-FIB-EDX methodologies complete the study and bring us closer to the composition of the alloys and the embroidery manufacture techniques. This technique actualizes the VIMP data and evidences the morphological and elemental differences between them; in particular, it is confirmed that Au-Ag-Cu alloys, with notably differences in Ag content depending on the provenance, were used.Projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2P, which are supported with Ministerio de Economia, Industria y Competitividad (MINECO), and Fondo Europeo de Desarrollo Regional (ERDF) funds, as well as project CTQ2017-85317-C2-1-P supported with funds from MINECO, ERDF, and Agencia Estatal de Investigacion (AEI), are gratefully acknowledged.Martínez, B.; Piquero-Cilla, J.; Domenech Carbo, MT.; Montoya, N.; Doménech Carbó, A. (2018). Electrochemical analysis of gold embroidery threads from archeological textiles. Journal of Solid State Electrochemistry. 22(7):2205-2215. https://doi.org/10.1007/s10008-018-3927-xS22052215227Járó M (2003). 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