The surface chemical composition effect of a polyacrylic acid/polyvinyl alcohol nanofiber/quartz crystal microbalance sensor on ammonia sensing behavior.

Polyacrylic acid (PAA)/polyvinyl alcohol (PVA)-based quartz crystal microbalance (QCM) ammonia sensors were fabricated by depositing composite PAA/PVA nanofibrous substrates onto QCM gold electrodes. Morphological analysis of the PAA/PVA substrates revealed a homogenous smooth surface and similar specific surface areas. X-ray photoelectron spectroscopy results indicated their distinct chemical properties with different carboxyl group contents on the surface. The ammonia sensing tests demonstrated the significant effect of the surface chemical characteristics on ammonia-sensing sensitivity, and the sensing process was proven to be derive from a monolayer adsorption mechanism. Because of the inherent high specific surface areas (SSAs) and three-dimensional porous architecture, the prepared PAA/PVA nanofiber-based QCM sensors exhibited ultrahigh sensitivity (100 ppb) and rapid response (several seconds) with good selectivity and repeatability in terms of ammonia detection.