Role of Solution and Surface Coverage on Voltage-Induced Response of Low-Density Self-Assembled Monolayers

Low-density self-assembled monolayers (LD-SAMs) exhibit voltage-induced conformational changes leading to tunable wetting properties and ionic permeability. Here we investigate the role of solution conditions (pH, salt concentration, presence of acetonitrile) and surface coverage via nonfaradaic electrochemical impedance spectroscopy and contact angle measurements. We observe a large change in receding angle (32) in an aqueous environment for an optimal combination of solution and film composition. This voltage-induced response in wetting properties is also correlated with a large change in dielectric properties as measured from electrochemical impedance spectroscopy. Our results demonstrate that the molecular nature of this responsive surface makes it particularly sensitive to solution conditions, a feature that could be exploited for sensing or detection.