Development of an ammonia sensor based on silver nanoparticles in a poly-methacrylic acid matrix.

Samples of Ag nanoparticles (AgNPs) in a poly-methacrylic acid (PMA) matrix have been prepared by a photo-induced reduction process. They have been widely characterized by SEM, EDX-mapping, TEM, XRD and XPS measurements. The results have shown that the morphological and microstructural characteristics of AgNPs formed in a PMA matrix depend on the Ag/PMA molar ratio. Thick films of these samples deposited on ceramic substrates have also been prepared. The formation of Ag dendritic structures has been evidenced in samples with a low Ag/PMA ratio, whereas at a higher Ag/PMA ratio the film surface was found to be highly heterogeneous, along with an increase in Ag species in the ionic form. Loading AgNPs/PMA samples with multi-walled carbon nanotubes (MWCNTs) allowed production of conductive films suitable for sensing applications. The samples synthesized were investigated as sensing materials for fabricating ammonia (NH₃) gas resistive sensors. The novel sensors developed are active at low temperature, exhibiting fast response/recovery times in a wide range of detection levels from ppm to v/v (%). [ABSTRACT FROM AUTHOR]