Electro- and photochemical studies of gold (III) bromide towards a novel laser-based method of gold patterning

Abstract In this report, we demonstrate a novel technique for the microscopic patterning of gold by combining the photoreduction of Au^IIIBr₄^- to Au^IBr₂^- and the electrochemical reduction of Au^IBr₂^- to elemental gold in a single step within solution. While mask-based methods have been the norm for electroplating, the adoption of direct laser writing for flexible, real-time patterning has not been widespread. Through irradiation using a 405 nm laser and applying a voltage corresponding to a selective potential window specific to Au^IBr₂^-, we have shown that we can locally deposit elemental gold at the focal point of the laser. In addition to demonstrating the feasibility of the technique, we have collected data on the kinetics of the photoreduction reaction in ethanol and have deduced its rate law. We have confirmed the selective deposition of Au^IBr₂^- within a potential window through controlled potential electrolysis experiments and through direct measurement on a quartz crystal microbalance. Finally, we have verified local deposition through scanning electron microscopy.