Indirect Optical and Electrochemical Detection of Trace Metals at Electrodeposited Sol-gel Films

Abstract

Spectroelectrochemical sensing provides three simultaneous modes of enhanced selectivity: chemically selective films, spectroscopy, and electrochemistry. Chemically selective sol-gels films are particularly useful in applications demanding optical transparency. Sol-gels have traditionally been deposited by means of spin or dip coating, limiting their use in applications where spatial resolution is desired. This work utilizes indium-tin oxide optically transparent electrodes for electrochemical deposition of pyridine functionalized sol-gel films. Functionalization can be tailored for chemical selectivity and sol-gels are deposited locally where potential is applied to catalyze sol-gel formation. The system studied in this work provides tri-modal selectivity by means of charge exclusion, electrochemical activity, and/or optical properties of the redox probe, Ru(bpy)₃²⁺. Spectroelectrochemical sensing can be applied for the indirect detection of ppb level Cr⁶⁺ based on pH dependent charge exclusion properties of the sol-gel films.