In Situ Spectroelectrochemistry at Free-Standing Liquid-Liquid Interfaces: UV-vis Spectroscopy, Microfocus X-ray Absorption Spectroscopy, and Fluorescence Imaging

A windowless electrochemical cell for the spectroscopic investigation of the liquid-liquid interface, using a dual droplet configuration, has been designed. The setup permits in situ probing of the bulk solutions and the interfacial region by fiber-optic UV-vis spectroscopy, microfocus X-ray fluorescence (XRF) elemental mapping, and microfocus X-ray absorption near-edge structure (mu XANES) spectroscopy. The electrodeposition of Au, induced by ion transfer of the tetrachloroaurate complex from a halogenated solvent (containing a weak reducing agent) to the aqueous phase, has been monitored by a combination of the three techniques. The reaction can be followed in situ by UV-vis spectroscopy by detecting the oxidized form of the reducing agent. Voltammetric evidence suggests the formation of interfacial Au(I) species, whereas mu XANES detect the presence of metallic Au(0).