Electroconductive silver nanoparticle composite films for sensing ammonia in the presence of water vapor

Abstract

Nanocomposite films (NCF) containing silver nanoparticles (AgNPs) separated by thin silica/poly-4-vinylpyridine/polyvinylpyrrolidone polymer layers were fabricated on several substrates by spin coating, dip coating, and drop casting methods. The films exhibit electrical conductivity that changes upon the exposure to moist ammonia and water vapors. Hydrogen bonding of ammonia and water molecules to the silica/polymer layers as well as the direct adsorption of ammonia molecules onto the silver surface accounted for the conductivity changes. Drop casting on nylon filter membranes resulted in the most reproducible films. Optical microscopy, atomic force microscopy, UV-Vis spectroscopy, SEM, and XRD were used for the characterization of the NCF. NCF fabricated with polyvinylpyrrolidone polymer layers exhibited 0.4 ppm limit of detection for ammonia in the presence of interfering water vapor. It is proposed that the films could be further developed as ammonia sensors for environmental and biomedical applications.