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

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

Aplicación de la técnica de microscopia electrónica de barrido de emisión de campo con haz de iones focalizado-microanálisis de rayos x a colecciones numismáticas

Los objetos metálicos, y en particular, las colecciones numismáticas, han sido el objeto de estudio de numerosas investigaciones arqueométricas centradas en el conocimiento de las sociedades del pasado, ya que de éstos es posible obtener una gran cantidad de información relativa a los usos y desarrollo tecnológico de esas civilizaciones a través de su procedencia, el proceso de manufactura o las materias primas empleadas. Las técnicas de análisis aplicadas para este fin han ido evolucionando con el tiempo, de forma que, actualmente, además del estudio metalográfico, se dispone de un amplio abanico de técnicas instrumentales que proporcionan información acerca de la composición, estructura y morfología del objeto metálico. En este trabajo se ha explorado las posibilidades de un nuevo método de análisis de colecciones numismáticas basado en el uso del Microscopio Electrónico de Barrido de Emisión de Campo con Haz de Iones Focalizado y Microanálisis de Rayos X (FESEM-FIB-EDX). Entre las ventajas que ofrece esta técnica, aplicada por primera vez en el estudio de objetos de metal arqueológico, está su carácter mínimamente invasivo para las piezas ya que no requiere toma de muestra y la alteración producida en el objeto se sitúa en la escala nanoscópica.La presente investigación está financiada con el proyecto I+D: “Aplicación de las técnicas nanoelectroquimicas y biotecnologías en el estudio y conservación del patrimonio en metal” Referencia: CTQ2014-53736-C3 cofinanciado con fondos FEDER adscrito al Programa estatal de fomento de la investigación científica y técnica de excelencia, subprograma estatal de generación del conocimiento, MINECO. (2015-2017). Los autores agradecen la colaboración de Dr. José Luis Moya y Manuel Planes, técnicos responsables del Servicio de Microscopía Electrónica de la Universitat Politècnica de València.Álvarez Romero, C.; Domenech Carbo, MT. (2017). Aplicación de la técnica de microscopia electrónica de barrido de emisión de campo con haz de iones focalizado-microanálisis de rayos x a colecciones numismáticas. Arché. (11 - 12):65-70. http://hdl.handle.net/10251/101195657011 - 1

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

Characterization of additives of PVAc and acrylic waterborne dispersions and paints by analytical Py-GC-MS and Py-Silylation-GC-MS

[EN] Commercial formulations of poly(vinyl acetate) (PVAc) and acrylic dispersions and paints commonly used by artists include a number of additives such as surfactants, coalescing agents, defoamers and thickeners, which are designed for improving shelf-life, as well as chemical and physical properties of the resulting product. Recent studies have shown that additives present in paints play an important role in the alteration processes undergone by the painting during ageing and further in cleaning tasks planed in conservation interventions. However, the identification of additives is a difficult task due to the elusive character of these substances present at low concentration in the paint. In this context, a four-step approach is proposed that includes analysis of paint samples together with analysis of their water extracted products by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and pyrolysis-silylation-gas chromatography-mass spectrometry (Py-silylation-GC-MS). This analytical strategy enables a better characterization of common additives present in commercial PVAc and acrylic paints and dispersions. In particular, the analysis of water soluble extracts, which are mainly composed by paint additives, avoids the interference of the major polymer pyrolizates. Experimental conditions concerning sample preparation and instrumental working conditions of both Py-GC techniques are optimized. Both acrylic and PVAc paints presented poly(ethylene oxide) (POE) type fragments dominating the background of their pyrograms, especially when derivatized by means of hexamethyldisilazane (HMDS). For the first time, additives such as alkyl sulfate and alkyl ether sulfate with C-10 and C-12 alkyl chains, poly(ethoxylate) fatty alcohol and octylphenyl poly(ethoxylate) surfactants were identified, as well as polyvinyl alcohol (PVOH) protective colloids, hydrophobically modified ethoxylated urethane (HEUR) thickeners an defoamers. Their major fragments and corresponding mass spectra are discussed. (C) 2015 Elsevier B.V. All rights reserved.Financial support from the MINECO Projects CTQ2011-28079-CO3-01 and CTQ2014-53736-C3-1-P, which are supported with ERDF funds, is gratefully acknowledged.Silva, MF.; Domenech Carbo, MT.; Osete Cortina, L. (2015). Characterization of additives of PVAc and acrylic waterborne dispersions and paints by analytical Py-GC-MS and Py-Silylation-GC-MS. Journal of Analytical and Applied Pyrolysis. 113:606-620. https://doi.org/10.1016/j.jaap.2015.04.011S60662011

Dating archaeological copper using electrochemical impedance spectroscopy. Comparison with voltammetry of microparticles dating

[EN] A methodology for dating copper/bronze archaeological objects aged under atmospheric environments using electrochemical impedance spectroscopy (EIS) is described. The method is based on the measurement of resistance associated to the growth of corrosion layers in EIS recorded upon immersion of the pieces in mineral water and applying a bias potential for the reduction of dissolved oxygen. Theoretical expressions for the time variation of such resistance following a potential rate law are presented. Equivalent expressions are derived and applied for estimating the variation of the tenorite/cuprite ratio from their specific voltammetric signals using voltammetry of microparticles data. Calibration curves were constructed from a set of well-documented coins.Financial support from the MEC Projects CTQ2011-28079-CO3-01 and 02 and CTQ2014-53736-C3-2-P which are supported with ERDF funds is gratefully acknowledged.Domenech Carbo, A.; Capelo, S.; Piquero-Cilla, J.; Domenech Carbo, MT.; Barrio, J.; Fuentes, A.; Al Sekhaneh, W. (2016). Dating archaeological copper using electrochemical impedance spectroscopy. Comparison with voltammetry of microparticles dating. Materials and Corrosion. 67(2):120-129. https://doi.org/10.1002/maco.201408048S120129672Friedman, I., & Smith, R. L. (1960). Part I, The Development of the Method. American Antiquity, 25(4), 476-493. doi:10.2307/276634Reich, S., Leitus, G., & Shalev, S. (2003). Measurement of corrosion content of archaeological lead artifacts by their Meissner response in the superconducting state; a new dating method. New Journal of Physics, 5, 99-99. doi:10.1088/1367-2630/5/1/399Scholz, F., Schröder, U., Meyer, S., Brainina, K. Z., Zakhachuk, N. F., Sobolev, N. V., & Kozmenko, O. A. (1995). The electrochemical response of radiation defects of non-conducting materials An electrochemical access to age determinations. Journal of Electroanalytical Chemistry, 385(1), 139-142. doi:10.1016/0022-0728(94)03840-yDoménech-Carbó, A., Labuda, J., & Scholz, F. (2012). Electroanalytical chemistry for the analysis of solids: Characterization and classification (IUPAC Technical Report). Pure and Applied Chemistry, 85(3), 609-631. doi:10.1351/pac-rep-11-11-13Doménech-Carbó, A., Doménech-Carbó, M. T., & Costa, V. (Eds.). (2009). Electrochemical Methods in Archaeometry, Conservation and Restoration. Monographs in Electrochemistry. doi:10.1007/978-3-540-92868-3Doménech-Carbó, A., Doménech-Carbó, M. T., & Peiró-Ronda, M. A. (2011). Dating Archeological Lead Artifacts from Measurement of the Corrosion Content Using the Voltammetry of Microparticles. Analytical Chemistry, 83(14), 5639-5644. doi:10.1021/ac200731qDoménech-Carbó, A., Doménech-Carbó, M. T., Capelo, S., Pasíes, T., & Martínez-Lázaro, I. (2014). Dating Archaeological Copper/Bronze Artifacts by Using the Voltammetry of Microparticles. Angewandte Chemie International Edition, 53(35), 9262-9266. doi:10.1002/anie.201404522Benarie, M., & Lipfert, F. L. (1986). A general corrosion function in terms of atmospheric pollutant concentrations and rain pH. Atmospheric Environment (1967), 20(10), 1947-1958. doi:10.1016/0004-6981(86)90336-7Strandberg, H. (1998). Reactions of copper patina compounds—II. influence of sodium chloride in the presence of some air pollutants. Atmospheric Environment, 32(20), 3521-3526. doi:10.1016/s1352-2310(98)00058-2Cano, E., Lafuente, D., & Bastidas, D. M. (2009). Use of EIS for the evaluation of the protective properties of coatings for metallic cultural heritage: a review. Journal of Solid State Electrochemistry, 14(3), 381-391. doi:10.1007/s10008-009-0902-6Hernandez-Escampa, M., Gonzalez, J., & Uruchurtu-Chavarin, J. (2009). Electrochemical assessment of the restoration and conservation of a heavily corroded archaeological iron artifact. Journal of Applied Electrochemistry, 40(2), 345-356. doi:10.1007/s10800-009-0003-3Angelini, E., Grassini, S., Parvis, M., & Zucchi, F. (2011). An in situ investigation of the corrosion behaviour of a weathering steel work of art. Surface and Interface Analysis, 44(8), 942-946. doi:10.1002/sia.3842Grassini, S., Angelini, E., Parvis, M., Bouchar, M., Dillmann, P., & Neff, D. (2013). An in situ corrosion study of Middle Ages wrought iron bar chains in the Amiens Cathedral. Applied Physics A, 113(4), 971-979. doi:10.1007/s00339-013-7724-1Doménech-Carbó, A., Doménech-Carbó, M. T., Peiró-Ronda, M. A., Martínez-Lázaro, I., & Barrio-Martín, J. (2012). Application of the voltammetry of microparticles for dating archaeological lead using polarization curves and electrochemical impedance spectroscopy. Journal of Solid State Electrochemistry, 16(7), 2349-2356. doi:10.1007/s10008-012-1668-9Degrigny, C., Guibert, G., Ramseyer, S., Rapp, G., & Tarchini, A. (2009). Use of E corr vs time plots for the qualitative analysis of metallic elements from scientific and technical objects: the SPAMT Test Project. Journal of Solid State Electrochemistry, 14(3), 425-435. doi:10.1007/s10008-009-0890-6Souissi, N., Bousselmi, L., Khosrof, S., & Triki, E. (2004). Voltammetric behaviour of an archeaological bronze alloy in aqueous chloride media. Materials and Corrosion, 55(4), 284-292. doi:10.1002/maco.200303719Souissi, N., Triki, E., Bousselmi, L., & Khosrof, S. (2006). Comparaison between archaeological and artificially aged bronze interfaces. Materials and Corrosion, 57(10), 794-799. doi:10.1002/maco.200503974Souissi, N., & Triki, E. (2009). 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Long-term atmospheric corrosion monitoring. Materials and Corrosion, 51(2), 104-108. doi:10.1002/(sici)1521-4176(200002)51:23.0.co;2-vBalasubramaniam, R., Laha, T., & Srivastava, A. (2004). Long term corrosion behaviour of copper in soil: A study of archaeological analogues. Materials and Corrosion, 55(3), 194-202. doi:10.1002/maco.200303723Natesan, M., Venkatachari, G., & Palaniswamy, N. (2006). Kinetics of atmospheric corrosion of mild steel, zinc, galvanized iron and aluminium at 10 exposure stations in India. Corrosion Science, 48(11), 3584-3608. doi:10.1016/j.corsci.2006.02.006Doménech, A., Doménech-Carbó, M. T., Pasies, T., & del Carmen Bouzas, M. (2012). Modeling Corrosion of Archaeological Silver-Copper Coins Using the Voltammetry of Immobilized Particles. Electroanalysis, 24(10), 1945-1955. doi:10.1002/elan.201200252Rosas-Camacho, O., Uquidi-Macdonald, M., & Macdonald, D. D. (2009). Deterministic Modeling of the Corrosion of Low-Carbon Steel by Dissolved Carbon Dioxide and the Effect of Acetic Acid. I-Effect of Carbon Dioxide. doi:10.1149/1.3259806Macdonald, D., & Englehardt, G. (2010). The Point Defect Model for Bi-Layer Passive Films. doi:10.1149/1.3496427Sharifi-Asl, S., Taylor, M. L., Lu, Z., Engelhardt, G. R., Kursten, B., & Macdonald, D. D. (2013). Modeling of the electrochemical impedance spectroscopic behavior of passive iron using a genetic algorithm approach. Electrochimica Acta, 102, 161-173. doi:10.1016/j.electacta.2013.03.143Macdonald, D. D. (2011). The history of the Point Defect Model for the passive state: A brief review of film growth aspects. Electrochimica Acta, 56(4), 1761-1772. doi:10.1016/j.electacta.2010.11.005Doménech-Carbó, A., Lastras, M., Rodríguez, F., Cano, E., Piquero-Cilla, J., & Osete-Cortina, L. (2013). Monitoring stabilizing procedures of archaeological iron using electrochemical impedance spectroscopy. 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Layer-by-layer identification of copper alteration products in metallic works of art using the voltammetry of microparticles. Analytica Chimica Acta, 680(1-2), 1-9. doi:10.1016/j.aca.2010.09.002Doménech, A., Doménech-Carbó, M. T., Pasies, T., & Bouzas, M. C. (2011). Application of Modified Tafel Analysis to the Identification of Corrosion Products on Archaeological Metals Using Voltammetry of Microparticles. Electroanalysis, 23(12), 2803-2812. doi:10.1002/elan.201100577Li, W. S., Cai, S. Q., & Luo, J. L. (2004). Chronopotentiometric Responses and Capacitance Behaviors of Passive Film Formed on Iron in Borate Buffer Solution. Journal of The Electrochemical Society, 151(4), B220. doi:10.1149/1.1667521Liu, W., Zhang, H., Qu, Z., Zhang, Y., & Li, J. (2009). Corrosion behavior of the steel used as a huge storage tank in seawater. Journal of Solid State Electrochemistry, 14(6), 965-973. doi:10.1007/s10008-009-0886-2Toledo-Matos, L. A., & Pech-Canul, M. A. (2010). 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Influence of plasticizer and biocide on the functional properties of gelatin-based adhesives used in painting consolidation

The study presented herein focuses on the influence of glycerol and citronella oil, added to gelatin dispersions as plasticizer and biocide, respectively, on the mechanical, water barrier and other functional properties of gelatin-based adhesives used in treatments of painting consolidation. For this purpose, ATR-FTIR spectroscopy, gas chromatography mass spectrometry, atomic force microscopy analyses combined with tensile, water vapour permeability, water content and water solubility tests were performed on gelatin films prepared by adding glycerol and citronella oil. These two products were chosen for their low toxicity and eco-friendly properties. The modification in the behaviour of gelatin-based adhesives as a result of addition of glycerol and citronella oil was evaluated on the basis of changes of the three-dimensional structure of the protein molecules due to their interaction with glycerol and citronella oil. All these data were provided by the analytical techniques. In a second step, stability of the proposed adhesive to light was assessed to establish its suitability for painting consolidation. The results suggest that citronella oil enhances the effectiveness of glycerol to improve mechanical behaviour and reversibility of the gelatine-based adhesive. Light ageing of the specimens containing the proposed additives produced no remarkable changes in structure, mechanical, water barrier and other functional properties of the adhesives.Financial support is gratefully acknowledged from the Spanish 'I+D+I MICINN' projects CTQ2011-28079-CO3-01 supported by ERDEF funds.Domenech Carbo, MT.; Lee, Y.; Osete Cortina, L.; Martín Rey, S. (2015). Influence of plasticizer and biocide on the functional properties of gelatin-based adhesives used in painting consolidation. Journal of Adhesion Science and Technology. 29(17):1774-1795. https://doi.org/10.1080/01694243.2014.975999S17741795291

Electrochemical analysis of gildings in Valencia altarpieces: a cross-age study since fifteenth until twentieth century, Journal of Solid State Electrochemistry

[EN] The application of the voltammetry of microparticles methodology to the study of gildings in paintings and architectural ornaments is described. Nanosamples from pieces from different churches of the Comunitat Valenciana (Spain) covering since the fifteenth century until nowadays were studied upon attachment to graphite electrodes in contact with aqueous HCl and H2SO4 electrolytes. Electrochemical measurements, combined with field emission scanning electron microscopy X-ray microanalysis (FESEM-EDX) and atomic force microscopy (AFM) data, denoted that a common manufacturing technique was used with minimal variations along time. The relationship between specific voltammetric features associated to bulk gold and active surface sites, however, changed monotonically with time, thus suggesting the possibility of age monitoring.Financial support from the MINECO Projects CTQ2014-53736-C3-1-P, CTQ2014-53736-C3-2-P and MAT2015-65445-C2-2-R, which are supported with ERDF funds is gratefully acknowledged. Likewise financial support of the Comunidad de Madrid and structural funds of the EU through Programa Geomateriales 2 ref. S2013/MIT-2914 is acknowledged. The authors thank the Seccion de Investigacion Arqueologica Municipal de Valencia for kindly authorizing sampling to carry out this research. The authors also thank Dr. Jose Luis Moya Lopez and Mr. Manuel Planes Insausti (Microscopy Service of the Universitat Politecnica de Valencia) for their technical support.Ferragud Adam, JV.; Piquero-Cilla, J.; Domenech Carbo, MT.; Guerola Blay, V.; Company Climent, J.; Domenech Carbo, A. (2016). 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Evaluación del empleo de biocidas naturales en mezclas adhesivas de base proteica

Los adhesivos naturales empleados en la consolidación de estratos pictóricos, son fácilmente deteriorados por microorganismos y bacterias debido a su composición orgánica. Las soluciones empleadas hasta el momento para su conservación, se fundamentan en la adición de un biocida, que otorgue mayor estabilidad a la mezcla, mejorando así su estabilidad física y química. Estos biocidas, habitualmente son agentes desinfectantes o pesticidas de amplio uso industrial, con graves problemas de toxicidad y peligrosidad para el usuario y su entorno. Progresivamente se han ido mejorando estas formulaciones, adaptándolas a los requerimientos exigidos en intervención del Patrimonio Cultural, pero sin detenerse en el riesgo que su empleo supone para el restaurador. En este estudio, se valoran diferentes bactericidas naturales como alternativa a los materiales más tóxicos empleados actualmente, analizando el poder insecticida o fungistático de cada uno de ellos y su miscibilidad con consolidantes pictóricos de tipo proteico. Concretamente se ha desarrollado el análisis comparativo entre cinco biocidas (Extracto de equinácea, propóleo, esencia de citronella, esencia de ajo y esencia de alcanfor), adicionados a dos tipos de gelatinas animales. Se ha valorado su empleo para los trabajos de consolidación de las policromías sobre madera del Templo Longshan (Lukang, Taiwán), con problemas puntuales de desconsolidación en algunas zonas y en otros casos de cohesión entre sustratos. El objetivo principal se ha fundamentado en la obtención de mezclas adhesivas estables desde el punto de vista de la Conservación y Restauración de los Bienes Culturales, a la vez que atóxicas para el restaurador y el medioambiente.Martín Rey, S.; Lee, Y.; Domenech Carbo, MT. (2011). Evaluación del empleo de biocidas naturales en mezclas adhesivas de base proteica. Arché. (6):273-278. http://hdl.handle.net/10251/34064273278

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.Financial support is gratefully acknowledged from the MEC Projects CTQ2011-28079-CO3-01 and 02 which are also supported with ERDF funds.Domenech Carbo, A.; Valle-Algarra, FM.; Domenech Carbo, MT.; Osete Cortina, L.; Domine, ME. (2013). Maya chemistry of organic inorganic hybrid materials: isomerization, cyclicization and redox tuning of organic dyes attached to porous silicates. RSC Advances. 3:20099-20105. https://doi.org/10.1039/c3ra42890gS20099201053Gómez-Romero, P., & Sanchez, C. (2005). Hybrid materials. Functional properties. From Maya Blue to 21st century materials. New J. Chem., 29(1), 57-58. doi:10.1039/b416075bCalzaferri, G., Huber, S., Maas, H., & Minkowski, C. (2003). Host–Guest Antenna Materials. Angewandte Chemie International Edition, 42(32), 3732-3758. doi:10.1002/anie.200300570Doménech, A., Doménech-Carbó, M. T., Sánchez del Río, M., Vázquez de Agredos Pascual, M. L., & Lima, E. (2009). Maya Blue as a nanostructured polyfunctional hybrid organic–inorganic material: the need to change paradigms. New Journal of Chemistry, 33(12), 2371. doi:10.1039/b901942aHubbard, B., Kuang, W., Moser, A., Facey, G. A., & Detellier, C. (2003). Structural study of Maya Blue: textural, thermal and solidstate multinuclear magnetic resonance characterization of the palygorskite-indigo and sepiolite-indigo adducts. Clays and Clay Minerals, 51(3), 318-326. doi:10.1346/ccmn.2003.0510308Fois, E., Gamba, A., & Tilocca, A. (2003). On the unusual stability of Maya blue paint: molecular dynamics simulations. Microporous and Mesoporous Materials, 57(3), 263-272. doi:10.1016/s1387-1811(02)00596-6Sánchez del Río, M., Martinetto, P., Somogyi, A., Reyes-Valerio, C., Dooryhée, E., Peltier, N., … Dran, J.-C. (2004). Microanalysis study of archaeological mural samples containing Maya blue pigment. Spectrochimica Acta Part B: Atomic Spectroscopy, 59(10-11), 1619-1625. doi:10.1016/j.sab.2004.07.027Giustetto, R., Llabrés i Xamena, F. X., Ricchiardi, G., Bordiga, S., Damin, A., Gobetto, R., & Chierotti, M. R. (2005). Maya Blue:  A Computational and Spectroscopic Study. The Journal of Physical Chemistry B, 109(41), 19360-19368. doi:10.1021/jp048587hDoménech, A., Doménech-Carbó, M. T., & Vázquez de Agredos Pascual, M. L. (2006). Dehydroindigo:  A New Piece into the Maya Blue Puzzle from the Voltammetry of Microparticles Approach. The Journal of Physical Chemistry B, 110(12), 6027-6039. doi:10.1021/jp057301lDoménech, A., Doménech-Carbó, M. T., & Vázquez de Agredos Pascual, M. L. (2007). Indigo/Dehydroindigo/Palygorskite Complex in Maya Blue:  An Electrochemical Approach. The Journal of Physical Chemistry C, 111(12), 4585-4595. doi:10.1021/jp067369gDoménech, A., Doménech-Carbó, M. T., & de Agredos Pascual, M. L. V. (2007). Chemometric Study of Maya Blue from the Voltammetry of Microparticles Approach. Analytical Chemistry, 79(7), 2812-2821. doi:10.1021/ac0623686DOMÉNECH, A., DOMÉNECH-CARBÓ, M. T., & VÁZQUEZ DE AGREDOS PASCUAL, M. L. (2009). CORRELATION BETWEEN SPECTRAL, SEM/EDX AND ELECTROCHEMICAL PROPERTIES OF MAYA BLUE: A CHEMOMETRIC STUDY*. Archaeometry, 51(6), 1015-1034. doi:10.1111/j.1475-4754.2009.00453.xDoménech, A., Doménech-Carbó, M. T., & Vázquez de Agredos-Pascual, M. L. (2011). From Maya Blue to «Maya Yellow»: A Connection between Ancient Nanostructured Materials from the Voltammetry of Microparticles. Angewandte Chemie International Edition, 50(25), 5741-5744. doi:10.1002/anie.201100921Doménech, A., Doménech-Carbó, M. T., Vidal-Lorenzo, C., & de Agredos-Pascual, M. L. V. (2011). Insights into the Maya Blue Technology: Greenish Pellets from the Ancient City of La Blanca. Angewandte Chemie International Edition, 51(3), 700-703. doi:10.1002/anie.201106562Doménech, A., Doménech-Carbó, M. T., Sánchez del Río, M., Goberna, S., & Lima, E. (2009). Evidence of Topological Indigo/Dehydroindigo Isomers in Maya Blue-Like Complexes Prepared from Palygorskite and Sepiolite. The Journal of Physical Chemistry C, 113(28), 12118-12131. doi:10.1021/jp900711kDoménech, A., Doménech-Carbó, M. T., del Río, M. S., & de Agredos Pascual, M. L. V. (2008). Comparative study of different indigo-clay Maya Blue-like systems using the voltammetry of microparticles approach. Journal of Solid State Electrochemistry, 13(6), 869-878. doi:10.1007/s10008-008-0616-1Doménech-Carbó, A., Doménech-Carbó, M. T., Valle-Algarra, F. M., Domine, M. E., & Osete-Cortina, L. (2013). On the dehydroindigo contribution to Maya Blue. Journal of Materials Science, 48(20), 7171-7183. doi:10.1007/s10853-013-7534-zDoménech-Carbó, A., Valle-Algarra, F. M., Doménech-Carbó, M. T., Domine, M. E., Osete-Cortina, L., & Gimeno-Adelantado, J. V. (2013). Redox Tuning and Species Distribution in Maya Blue-Type Materials: A Reassessment. ACS Applied Materials & Interfaces, 5(16), 8134-8145. doi:10.1021/am402193uRondão, R., Seixas de Melo, J. S., Bonifácio, V. D. B., & Melo, M. J. (2010). Dehydroindigo, the Forgotten Indigo and Its Contribution to the Color of Maya Blue. The Journal of Physical Chemistry A, 114(4), 1699-1708. doi:10.1021/jp907718kTilocca, A., & Fois, E. (2009). The Color and Stability of Maya Blue: TDDFT Calculations. The Journal of Physical Chemistry C, 113(20), 8683-8687. doi:10.1021/jp810945aGiustetto, R., Seenivasan, K., Bonino, F., Ricchiardi, G., Bordiga, S., Chierotti, M. R., & Gobetto, R. (2011). Host/Guest Interactions in a Sepiolite-Based Maya Blue Pigment: A Spectroscopic Study. The Journal of Physical Chemistry C, 115(34), 16764-16776. doi:10.1021/jp203270cGiustetto, R., & Wahyudi, O. (2011). Sorption of red dyes on palygorskite: Synthesis and stability of red/purple Mayan nanocomposites. Microporous and Mesoporous Materials, 142(1), 221-235. doi:10.1016/j.micromeso.2010.12.004Giustetto, R., Seenivasan, K., Pellerej, D., Ricchiardi, G., & Bordiga, S. (2012). Spectroscopic characterization and photo/thermal resistance of a hybrid palygorskite/methyl red Mayan pigment. Microporous and Mesoporous Materials, 155, 167-176. doi:10.1016/j.micromeso.2012.01.024Sánchez del Río, M., Boccaleri, E., Milanesio, M., Croce, G., van Beek, W., Tsiantos, C., … García-Romero, E. (2009). A combined synchrotron powder diffraction and vibrational study of the thermal treatment of palygorskite–indigo to produce Maya blue. Journal of Materials Science, 44(20), 5524-5536. doi:10.1007/s10853-009-3772-5Mondelli, C., Río, M. S. del, González, M. A., Magazzú, A., Cavallari, C., Suárez, M., … Romano, P. (2012). Role of water on formation and structural features of Maya blue. Journal of Physics: Conference Series, 340, 012109. doi:10.1088/1742-6596/340/1/012109Dejoie, C., Martinetto, P., Dooryhée, E., Strobel, P., Blanc, S., Bordat, P., … Anne, M. (2010). Indigo@Silicalite: a New Organic−Inorganic Hybrid Pigment. ACS Applied Materials & Interfaces, 2(8), 2308-2316. doi:10.1021/am100349bDejoie, C., Martinetto, P., Dooryhée, E., Brown, R., Blanc, S., Bordat, P., … Anne, M. (2011). Diffusion Of Indigo Molecules Inside The Palygorskite Clay Channels. MRS Proceedings, 1319. doi:10.1557/opl.2011.924Ovarlez, S., Giulieri, F., Chaze, A.-M., Delamare, F., Raya, J., & Hirschinger, J. (2009). The Incorporation of Indigo Molecules in Sepiolite Tunnels. Chemistry - A European Journal, 15(42), 11326-11332. doi:10.1002/chem.200901482Ovarlez, S., Giulieri, F., Delamare, F., Sbirrazzuoli, N., & Chaze, A.-M. (2011). Indigo–sepiolite nanohybrids: Temperature-dependent synthesis of two complexes and comparison with indigo–palygorskite systems. Microporous and Mesoporous Materials, 142(1), 371-380. doi:10.1016/j.micromeso.2010.12.025Franç, N. A., Giulieri, oise, Ovarlez, S., & Chaze, A. M. (2012). Indigo/sepiolite nanohybrids: stability of natural pigments inspired by Maya blue. International Journal of Nanotechnology, 9(3/4/5/6/7), 605. doi:10.1504/ijnt.2012.045334Tsiantos, C., Tsampodimou, M., Kacandes, G. H., Sánchez del Río, M., Gionis, V., & Chryssikos, G. D. (2011). Vibrational investigation of indigo–palygorskite association(s) in synthetic Maya blue. Journal of Materials Science, 47(7), 3415-3428. doi:10.1007/s10853-011-6189-xLima, E., Guzmán, A., Vera, M., Rivera, J. L., & Fraissard, J. (2012). Aged Natural and Synthetic Maya Blue-Like Pigments: What Difference Does It Make? The Journal of Physical Chemistry C, 116(7), 4556-4563. doi:10.1021/jp207602mKumagai, Y., Tsurutani, Y., Shinyashiki, M., Homma-Takeda, S., Nakai, Y., Yoshikawa, T., & Shimojo, N. (1997). Bioactivation of lapachol responsible for DNA scission by NADPH-cytochrome P450 reductase. Environmental Toxicology and Pharmacology, 3(4), 245-250. doi:10.1016/s1382-6689(97)00019-7Nasiri, H. R., Bolte, M., & Schwalbe, H. (2008). Electrochemical and crystal structural analysis ofα- and dehydro-α-lapachones. Natural Product Research, 22(14), 1225-1230. doi:10.1080/14786410701654925Garkavtsev, I., Chauhan, V. P., Wong, H. K., Mukhopadhyay, A., Glicksman, M. A., Peterson, R. T., & Jain, R. K. (2011). Dehydro- -lapachone, a plant product with antivascular activity. 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