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

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

Superior Electrocatalytic Activity of MoS2-Graphene as Superlattice

[EN] Evidence by selected area diffraction patterns shows the successful preparation of large area (cm x cm) MoS2/graphene heterojunctions in coincidence of the MoS2 and graphene hexagons (superlattice). The electrodes of MoS2/graphene in superlattice configuration show improved catalytic activity for H-2 and O-2 evolution with smaller overpotential of +0.34 V for the overall water splitting when compared with analogous MoS2/graphene heterojunction with random stacking.This research was funded by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2015-68653-CO2-R1) and Generalitat Valenciana (Prometeo 2017-083).Rendon-Patiño, A.; Domenech-Carbó, A.; Primo Arnau, AM.; García Gómez, H. (2020). Superior Electrocatalytic Activity of MoS2-Graphene as Superlattice. Nanomaterials. 10(5):1-9. https://doi.org/10.3390/nano10050839S1910

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). Metal threads in historical textiles, in Molecular and structural archaeology: Cosmetic and therapeutic chemicals, Centre de Recherche et de Restauration des Musées de France, Paris, pp 163−178Gleba M (2008) Auratae vestes: Gold textiles in the ancient Mediterranean, in Vestidos, Textiles y Tintes: Estudios sobre la produccion de bienes de consumo en la antigüedad, Proceedings of I Symposium Internacional sobre textiles y tintes del Mediterráneo en época romana, 2002. Consell Insular d‘Eivissa i Formentera and Universitat de Valencia,pp 63−80Járó M (1990) Gold embroidery and fabrics in europe: XI–XIV centuries. Gold Bull 23(2):40–57Karatzani A (2007) The evolution of a craft: the use of metal threads in the decoration of late and post Byzantine ecclesiastical textiles. University of London, LondonJáró M (1995) Manufacturing technique of gold threads and their imitations on museum textiles-chronology of the preparation of metal threads. Results of the scientific investigations in Endrei W, Ed. Yearbook of the Textile Museum, Budapest, pp 31−51Nord AG, Tronner K (2000) A note on the analysis of gilded metal embroidery threads. Stud Conservat 45:274–279Tronner K, Nord AG, Sjöstedt J, Hydman H (2002) Extremely thin gold layers on gilded silver threads. Stud Conservat 47:109–116Hoke E, Petrascheck-Heim I (1977) Microprobe analysis of gilded silver threads from mediaeval textiles. Stud in Conservat 22:49–62Indictor N, Koestler RJ, Blair C, Wardwell A (1988) The evaluation of metal warppings from medieval textiles using scanning electron microscoopy-energy dispersive X-ray spectrometry. Text Hist 19(1):3–22Indictor N, Koestler RJ, Wypyski M, Wardwell AE (1989) Metal threads made of proteinaceous substrates examined by scanning electron microscopy-energy dispersive x-ray spectrometry. Stud Conservat 34:171–182Karatzani A (2006). Metal threads: the historical development. Proceedings ISA: 444.09−444.19Járó M, Toth A, Gondar E (1990) Determination of the manufacturing technique of a 10th century metal thread. ICOM Committee for Conservation, 9th triennial meeting, Dresden, German Democratic Republic. ICOM Committee for Conservation, pp 299−301Enguita O, Climent-Font A, García G, Montero I, Fedi ME, Chiari M, Lucarelli F (2002) Characterization of metal threads using differential PIXE analysis. Nucl Inst Methods Phys Res B 189(1-4):328–333Balta ZI, Csedreki L, Furu E, Cretu I, Huszank R, Lupu M, Torok Z, Kertesz Z, Szikszai Z (2015) Ion beam analysis of golden threads from Romanian medieval textiles. Nucl Inst Methods Phys Res B 348:285–290Pascual-Pacheco J (1992) La necrópolis islámica de l’Almoina (Valencia). Primeros resultados. III CAME, Actas 2:406−412Pascual-Pacheco J, Serrano-Marcos ML (1996) Necrópolis islámicas en la ciudad de Valencia. Saitabi 46:231–252Ferragud-Adam X, Piquero-Cilla J, Doménech-Carbó MT, Guerola Blay V, Company X, Doménech-Carbó A (2017) Electrochemical analysis of gildings in Valencia altarpieces: a cross-age study since 15th until 20th century. J Solid State Electrochem 21:1477–1487Constantinescu B, Vasilescu A, Radtke M, Reinholz U (2010) Micro-SR-XRF studies for archaeological gold identification—the case of Carpathian gold and Romanian museal objects. Appl Phys A Mater Sci Process 99(2):383–389Antonelli F, Lazzarini L, Cancellere S, Tesser E (2016) Study of the deteriortion products, gilding, and polychromy of the stones of the Scuola Grande Di San Marco’s façade in Venice. Stud Conserv 61(2):74–85Gulotta D, Goidanich S, Bertoldi M, Bortolotto S, Toniolo L (2012) Gildings and false gildings of the baroque age: characterization and conservation problems. Archaeometry 54(5):940–954Scholz F, Meyer B (1998) Voltammetry of solid microparticles immobilized on electrode surfaces, Electroanalytical chemistry, a series of advances. Bard AJ, Rubinstein I, Eds., Marcel Dekker, New York, vol. 20, pp 1−86Scholz F, Schröder U, Gulaboski R, Doménech-Carbó A (2014) Electrochemistry of immobilized particles and droplets, 2nd edn. Springer, Berlin-HeidelbergDoménech-Carbó A, Labuda J, Scholz F (2013) Electroanalytical chemistry for the analysis of solids: characterization and classification (IUPAC Technical Report). Pure Appl Chem 85:609–631Doménech-Carbó A, Doménech-Carbó MT, Costa V (2009) Electrochemical methods in archaeometry, conservation and restoration. Monographs in electrochemistry series, Scholz F, Ed. Springer, Berlin-HeidelbergDoménech-Carbó A (2010) Voltammetric methods applied to identification, speciation and quantification of analytes from works of art: an overview. J Solid State Electrochem 14(3):363–369Doménech-Carbó A (2011) Tracing, authentifying and dating archaeological metal using the voltammetry of microparticles. Anal Methods 3(10):2181–2188Burke LD, Nugent PF (1997) The electrochemistry of gold: I the redox behaviour of the metal in aqueous media. Gold Bull 30(2):43–53Chen A, Lipkowski J (1999) Electrochemical and spectroscopic studies of hydroxide adsorption at the Au(111) electrode. J Phys Chem B 103(4):682–691Hoogvliet JC, van Bennekom WP (2001) Gold thin-film electrodes: an EQCM study of the influence of chromium and titanium adhesion layers on the response. Electrochim Acta 47(4):599–611Burke LD, O'Mullane AP (2000) Generation of active surface states of gold and the role of such states in electrocatalysis. J Solid State Electrochem 4(5):285–297Burke LD, O’Mullane AP, Lodge VE, Mooney MB (2001) Auto-inhibition of hydrogen gas evolution on gold in aqueous acid solution. J Solid State Electrochem 5(5):319–327Doyle RL, Lyons MEG (2014) The mechanism of oxygen evolution at superactivated gold electrodes in aqueous alkaline solution. J Solid State Electrochem 18(12):3271–3286Jeyabharathi C, Hasse U, Ahrens P, Scholz F (2014) Oxygen electroreduction on polycrystalline gold electrodes and on gold nanoparticle-modified glassy carbon electrodes. J Solid State Electrochem 18(12):3299–3306Jeyabharathi C, Ahrens P, Hasse U, Scholz F (2016) Identification of low-index crystal planes of polycrystalline gold on the basis of electrochemical oxide layer formation. J Solid State Electrochem 20(11):3025–3031Izumi T, Watanabe I, Yokoyama Y (1991) Activation of a gold electrode by electrochemical oxidation-reduction pretreatment in hydrochloric acid. J Electroanal Chem Interfacial Electrochem 303(1-2):151–160Scholz F, López de Lara González G, de Carvalho LM, Hilgemann M, Brainina Kh Z, Kahlert H, Jack RS, Minh DT (2007) Indirect electrochemical sensing of radicals and radical scavengers in biological matrices. Angew Chem Int Ed 46(42):8079–8081Nowicka A, Hasse U, Sievers G, Donten M, Stojek Z, Fletcher S, Scholz F (2010) Selective knockout of gold active sites. Angew Chem Int Ed 49(17):3006–3009Hasse U, Fricke K, Dias D, Sievers G, Wulff H, Scholz F (2012) Grain boundary corrosion of the surface of annealed thin layers of gold by OH·radicals. J Solid State Electrochem 16(7):2383–2389Hasse U, Wulff H, Helm CA, Scholz F (2013) Formation of gold surfaces with a strongly preferred {100}-orientation. J Solid State Electrochem 17(12):3047–3053Cepriá G, Abadías O, Pérez-Arantegui J, Castillo JR (2001) Electrochemical behavior of silver-copper alloys in voltammetry of microparticles: a simple method for screening purposes. Electroanalysis 13(6):477–483Doménech-Carbó A, Doménech-Carbó MT, Pasíes T, Bouzas MC (2012) Modeling corrosion of archaeological silver-copper coins using the voltammetry of immobilized particles. Electroanalysis 24:1945–1955Capelo S, Homem PM, Cavalheiro J, Fonseca ITE (2013) Linear sweep voltammetry: a cheap and powerful technique for the identification of the silver tarnish layer constituent. J Solid State Electrochem 17:223–234Doménech-Carbó A, Del Hoyo-Meléndez JM, Doménech-Carbó MT, Piquero-Cilla J (2017) Electrochemical analysis of the first Polish coins using the voltammetry of immobilized particles. Microchem J 130:47–55Jeyabharathi C, Hodnik N, Baldizzone C, Meier JC, Heggen M, Phani KLN, Bele M, Zorko M, Hocevar S, Mayrhofer KJJ (2013) Time evolution of the stability and oxygen reduction reaction activity of PtCu/C nanoparticles. ChemCatChem 5(9):2627–2635Meier JC, Galeano C, Katsounaros I, Topalov AA, Kostka A, Schuth F, Mayrhofer KJJ (2012) Degradation mechanisms of Pt/C fuel cell catalysts under simulated start–stop conditions. ACS Catal 2(5):832–843Meier JC, Katsounaros I, Galeano C, Bongard HJ, Topalov AA, Kostka A, Karschin A, Schuth F, Mayrhofer KJJ (2012) Stability investigations of electrocatalysts on the nanoscale. Energy Environ Sci 5(11):9319–9330Martí-Villaba M, Davis J (2008) New directions for carbon-based detectors: exploiting the versatility of carbon substrates in electroanalysis. J Solid State Electrochem 12:1245–1254Noked M, Soffer A, Aurbach D (2011) The electrochemistry of activated carbonaceous materials: past, present, and future. J Solid State Electrochem 15(7-8):1563–1578Kang F, Leng Y, Zhang T-Y, Li B (1998) Electrochemical synthesis and characterization of ferric chloride-graphite intercalation compounds in aqueous solution. Carbon 36(4):383–390Urbaniak J, Skowronski JM, Olejnik B (2010) Preparation of Fe2O3-exfoliated graphite composite and its electrochemical properties investigated in alkaline solution. J Solid State Electrochem 14(9):1629–1635Herrera-Gallego J, Castellano CE, Calandra AJ, Arvia AJ (1975) The electrochemistry of gold in acid aqueous solutions containing chloride ions. J Electroanal Chem 66(3):207–230Doménech-Carbó A, Scholz F, Schmitt RT, Usera J, García-Forner AM, De l F-A, Jeyabharathi C, Piquero-Cilla J, Montoya N (2017) Electrochemical characterization of natural gold samples using the voltammetry of immobilized particles. Electrochem Commun 85:23–2

Electrochemical analysis of the first Polish coins using voltammetry of immobilized particles

[EN] A series of 20 denarii from Boleslaus the Brave (992-1025) and Mieszko II Lambert (1025-1034), corresponding to the beginning of the Polish state were studied using the voltammetry of immobilized particles (VIMP) methodology. VIMP experiments, applied to nanosamples of the corrosion layers of the coins in contact with aqueous acetate buffer, provided well-defined responses mainly corresponding to the corrosion products of copper and lead. Such voltammetric responses, combined with X-ray fluorescence (XRF) spectroscopy experiments performed on the same set of coins, and complemented by focusing ion beam-field emission scanning electron microscope (FIB-FESEM) on silver coins from the 19th century, supported the hypothesis that two different metal sources were used in the former historical period and suggested that the coins were produced in three different mints. (C) 2016 Elsevier B.V. All rights reserve.Financial support from the MINECO Projects CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P which are supported with ERDF funds is gratefully acknowledged. The authors are very grateful to the Polish Ministry of Science and Higher Education for partly financing the work presented in this paper through a grant within the framework of the National Program for the Development of the Humanities (Decision No. 0100/NPRH3/H12/82/2014) and also wish to thank Dr. Jose Luis Moya Lopez and Mr. Manuel Planes Insausti (Microscopy Service of the Universitat Politecnica de Valencia) for technical support.Doménech Carbó, A.; Del Hoyo Meléndez, JM.; Domenech Carbo, MT.; Piquero-Cilla, J. (2017). Electrochemical analysis of the first Polish coins using voltammetry of immobilized particles. Microchemical Journal. 130:47-55. https://doi.org/10.1016/j.microc.2016.07.020S475513

Electrochemical identification of painters/workshops: The case of Valencian Renaissance-Baroque painters (ca. 1550- ca. 1670)

[EN] The voltammetry of immobilized particles (VIMP) methodology was applied to discriminate the oil painting production of a series of seven painters/workshops that worked in Valencia (Spain) between ca. 1530 and ca. 1650. When submicrosamples used for cross-section FESEM/EDX analysis were attached to graphite electrodes in contact with aqueous acetate buffer, well-defined responses were obtained. The reductive processes of lead pigments (lead white and lead-tin yellow) overlapped those associated to the lead soaps and other species resulting from the pigment-oil binder interaction in the sample. Such responses, which are theoretically modeled, were sensitive to changes in paint type and dose and thus provided a painter/workshop-characteristic voltammetric response defining a usable electrochemical fingerprint for authorship assessments. (C) 2018 Elsevier Ltd. All rights reserved.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. The authors wish also to thank Mr. Manuel Planes and Dr. Jose Luis Moya, technical supervisors of the Electron Microscopy Service of the Universitat Politecnica de Valencia.Doménech Carbó, A.; Domenech Carbo, MT.; Castelló Palacios, A.; Guerola Blay, V.; Pérez Marín, E. (2019). Electrochemical identification of painters/workshops: The case of Valencian Renaissance-Baroque painters (ca. 1550- ca. 1670). Electrochimica Acta. 297:685-695. https://doi.org/10.1016/j.electacta.2018.11.212S68569529

Microchemical surface analysis of historic copper-based coins by the combined use of FIB-FESEM-EDX, OM, FTIR spectroscopy and solid-state electrochemical techniques

[EN] A multi-technique strategy, including microscopy, spectroscopic and electrochemical techniques, is proposed to study thin corrosion layers that form on the surface of historic copper-based coins. An accurate characterisation of this external corrosion layer is important for selecting a suitable conservation and/or restoration treatment. For this purpose, a series of copper-based coins from different historical periods and provenances, which mainly exhibited atmospheric corrosion, was analysed. The morphology of the corrosion layer and the upper core of coins was studied in trenches done on coin surfaces with a focused ion beam gun, coupled to a field emission scanning electron microscope-X-ray microanalysis (FIB-FESEM-EDX). The X-ray microanalysis performed with FESEM-EDX on trenches allowed elemental composition profiles on the corrosion layer to be obtained. These results were complemented with the compositional data of the corrosion products provided by the voltammetry of immobilised microparticles (VIMP) and Fourier transform infrared spectroscopy (FTIR), and by studying visual appearance by optical microscopy and colorimetry. Cuprite and tenorite (the latter increased with coin age) were the main identified corrosion products, which were accompanied, to a lesser extent, by copper trihydroxychloride polymorphs. Interestingly, metal oxalates and metal-carboxylate complexes were identified on the corrosion layer of most coins. These unusual alteration products of copper-based coins were formed from the organic matter deposited on coin surfaces given their use when placed in circulation or by further manipulations of collectors.Financial support is gratefully acknowledged from the Spanish "R + D + I" project CTQ2017-85317-C2-1-P, CTQ2014-53736-C3-1-P and CTQ2014-53736-C3-2-P, which are supported by the Ministerio de Ciencia, Innovation y Universidades, Fondo Europeo de Desarrollo Regional (ERDF) funds and Agencia Estatal de Investigation (AEI). The authors wish to thank Mr. Manuel Planes, Dr. Jose Luis Moya and Mrs. Alicia Nuez Inbernon, technical supervisors of the Electron Microscopy Service of the Universitat Politecnica de Valencia.Domenech Carbo, MT.; Álvarez-Romero, C.; Doménech Carbó, A.; Osete Cortina, L.; Martínez Bazán, ML. (2019). Microchemical surface analysis of historic copper-based coins by the combined use of FIB-FESEM-EDX, OM, FTIR spectroscopy and solid-state electrochemical techniques. Microchemical Journal. 148:573-581. https://doi.org/10.1016/j.microc.2019.05.039S57358114

Hematite as an Electrocatalytic Marker for the Study of Archaeological Ceramic Clay bodies: A VIMP and SECM Study**

[EN] The electrocatalytic effect exerted by hematite, a ubiquitous component of clay bodies, on the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can be used to acquire information on archaeological ceramics. The solid-state voltammetric response of different hematite and ochre specimens, accompanied by SECM analysis in contact with 0.10 M HCl aqueous solution, is described. In air-saturated solutions, catalytic effects on the ORR and OER are accompanied by Fe(III)/Fe(II) and Fe(IV)/Fe(III) redox reactions. Such processes are conditioned by a variety of factors, the hydroxylation degree of the mineral surfaces being particularly influential, and exhibit significant variations upon heating the specimens between 300 and 900 degrees C. Voltammetric measurements carried out on a set of archaeological samples of Apulian red-figured pottery dated back within 5(th) and 4(th) centuries BCE permit to obtain site-characteristic voltammetric profiles.The work was carried out within the framework of project PID2020-113022GB-I00 which was financially support by Ministerio de Ciencia e Innovacion and Agencia Estatal de Investigacion (AEI) of the Spanish government.Doménech-Carbó, A.; Giannuzzi, M.; Mangone, A.; Giannossa, LC.; Di Turo, F.; Cofini, E.; Domenech Carbo, MT. (2022). Hematite as an Electrocatalytic Marker for the Study of Archaeological Ceramic Clay bodies: A VIMP and SECM Study**. ChemElectroChem. 9(2):59-68. https://doi.org/10.1002/celc.20210119759689

Acid Catalysis with Alkane/Water Microdroplets in Ionic Liquids

Ionic liquids are composed of an organic cation and a highly delocalized perfluorinated anion, which remain tight to each other and neutral across the extended liquid framework. Here we show that n-alkanes in millimolar amounts enable a sufficient ion charge separation to release the innate acidity of the ionic liquid and catalyze the industrially relevant alkylation of phenol, after generating homogeneous, self-stabilized, and surfactant-free microdroplets (1–5 μm). This extremely mild and simple protocol circumvents any external additive or potential ionic liquid degradation and can be extended to water, which spontaneously generates microdroplets (ca. 3 μm) and catalyzes Brönsted rather than Lewis acid reactions. These results open new avenues not only in the use of ionic liquids as acid catalysts/solvents but also in the preparation of surfactant-free, well-defined ionic liquid microemulsions.PNICTOCHEM 804110 (G.A.)PID2019-111742-GA-I00CIDEGENT/2018/00