Study of nanocomposite thin-film sensor materials

Currently, there is a growing need for environmental monitoring and industrial safety, and, accordingly, for cost-effective, selective and stable sensor systems capable of promptly detecting even low concentrations of toxic components. The paper presents the results of a study of thin-film sensor materials based on biopolymer matrices of polysaccharides modified with AgI nanoparticles. The materials are intended for highly sensitive determination of ammonia in the air. The relationship between the structural and morphological characteristics of composite films containing AgI nanoparticles and their functional sensory properties with respect to ammonia vapors was analyzed. Particular attention was paid to studying the mechanisms of sensory response and the effect of surface morphology on the sensitivity of the material. Atomic force microscopy and electrophysical measurements have shown that the introduction of AgI nanoparticles significantly modifies the film surface, forming a developed relief with nanoparticle agglomerates (50 – 200 nm in size), a porous structure and an increased specific surface area (roughness increases by 3 – 5 times). Such morphological changes have been shown to significantly increase the sensitivity of the material to ammonia due to an increase in the area of active adsorption centers. Ammonia is detected due to a reversible complexation reaction between Ag⁺ ions and NH₃ molecules, which changes the conductivity of the composite. High dynamic characteristics of the sensor have been established (the response time does not exceed 8 sec at an NH₃ concentration of 50 ppm, and the recovery time is about 30 sec). In addition, the developed materials are selective for ammonia in the presence of potential interferents (CO₂, H₂O, volatile organic compounds). The results obtained can be used to create a new generation of gas sensors.

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