Thin-Film Nanocomposite Sensor Materials

At present, there is a growing need for environmental monitoring and industrial safety, which gives rise to a demand for economically viable, selective, and stable sensor systems capable of rapidly detecting even low concentrations of toxic components. In this paper, we present results of a study of thin-film sensor materials based on biopolymer matrices produced from polysaccharides modified with AgI nanoparticles. The materials are intended for highly sensitive detection of ammonia in air. We analyze relationships between the structural and morphological characteristics of the composite films containing AgI nanoparticles and their functional sensing properties for ammonia gas detection. Special attention is paid to sensor response mechanisms and the effect of surface morphology on the sensitivity of the material. Atomic force microscopy results and electrical measurements demonstrate that the addition of AgI nanoparticles leads to significant modification of the film surface: the formation of high surface roughness, nanoparticle agglomerates (50 to 200 nm in size), and a porous structure and an increase in specific surface area (the roughness value increases by three to five times). Such morphological changes have been shown to significantly improve the ammonia sensitivity of the material as a result of the increase in the area of active adsorption centers. The ability to detect ammonia is due to a reversible complexation reaction between Ag+ ions and NH3 molecules, which leads to changes in the conductivity of the composite. The sensor has been shown to have excellent dynamic characteristics (the response time does not exceed 8 s at a NH3 concentration of 50 ppm and the recovery time is about 30 s). Moreover, the materials produced in this study offer selectivity for ammonia in the presence of potential interferents (CO2, H2O, and volatile organic compounds). The results of this study can be useful in designing a new generation of gas sensors.