Abstract
The indium tin oxide (ITO) material has been widely used in various scientific fields and has been successfully implemented in several devices. Herein, the electrochemical reduction of ITO electrode in an organic electrolytic solution containing alkali metal, NaI, or redox molecule, N-(ferrocenylmethyl) imidazolium iodide, was investigated. The reduced ITO surfaces were investigated by X-ray photoelectron spectroscopy and grazing incident XRD demonstrating the presence of the electrolyte cation inside the material. Reversibility of this process after re-oxidation was evidenced by XPS. Using a redox molecule based ionic liquid as supporting electrolyte leads to fellow electrochemically the intercalation process. As a result, modified ITO containing ferrocenyl imidazolium was easily generated. This reduction process occurs at mild reducing potential around −1.8 V and causes for higher reducing potential a drastic morphological change accompanied with a decrease of the electrode conductivity at the macroscopic scale. Finally, the self-reducing power of the reduced ITO phase was used to initiate the spontaneous reduction of silver ions leading to the growth of Ag nanoparticles. As a result, transparent and multifunctional active ITO surfaces were generated bearing redox active molecules inside the material and Ag nanoparticles onto the surface.
Highlights
Indium tin oxide (ITO) has been widely used as electrode material in various scientific fields
The change in the indium tin oxide (ITO) surface upon the cathodic treatment was investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and X-ray diffraction (XRD)
The cyclic voltammetry recorded on ITO electrode in acetonitrile (ACN) solution containing 0.1 M NaI displays a quasi-reversible redox system with a reduction peak potential at −2 V (Fig. 1a)
Summary
Surface Modification received: 01 August 2016 accepted: 19 October 2016 Published: 18 November 2016. The reduced ITO surfaces were investigated by X-ray photoelectron spectroscopy and grazing incident XRD demonstrating the presence of the electrolyte cation inside the material Reversibility of this process after re-oxidation was evidenced by XPS. Aliev et al reported the reversible superconductivity in electrochemically intercalated indium-tin oxide films[22,23] They investigate the effect of the electrochemical doping of ITO films with alkali metals, using anodic charging process, on the paramagnetic Meissner effect (PME). Another electrochemical process, less investigated and conduces to surface modification, is the electrochemical reduction of electrode materials in dry electrolytic solution. Our purpose in this work was to answer to several fundamental questions related to the electrochemical reduction of ITO in organic electrolytic solution, electrochemical reversibility of the process, the surface and chemical composition changes, and the use of the reduced material to induce self-reduction process
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