Converting Silver Electrodes into Porous Gold Counterparts: A Strategy to Enhance Gas Sensor Sensitivity and Chemical Stability via Electrode Engineering

Abstract

This chapter describes a strategy for sensitivity and chemical stability enhancement of chemiresistive gas sensors via electrode engineering. In this strategy, flexible chemiresistive gas sensors were fabricated by uniformly depositing functionalized semiconducting carbon nanotubes (CNTs) on a polyimide substrate via a novel layer-by-layer wet chemical method, followed by inkjet printing fine-featured silver interdigitated electrodes (IDEs) on the substrate. The electrode engineering was realized by converting the inkjet-printed IDEs into their highly porous and chemically stable gold counterparts via a mild and facile two-step process, with the substrate-IDE adhesion retained. As a proof-of-concept demonstration, a diethyl ethylphosphonate (DEEP, a simulant of the nerve agent sarin) sensor equipped with inkjet-printed dense silver IDEs was converted into its counterpart equipped with highly porous gold IDEs. The resulting gold-electrode gas sensor exhibited sensitivity to DEEP of at least fivefold higher than a similar sensor electrode with the dense silver IDEs. The sensitivity enhancement was probably due to the catalytic activity of the resulting gold IDEs, as well as the creation of the nano−/micro-scale pores in the gold IDEs that increased the Schottky contacts between the gold IDEs and the semiconducting CNTs.