Fabrication of silver nanoparticles/polyaniline composite thin films using Layer-by-Layer self-assembly technique for ammonia sensing

In this study, the Layer-by-Layer (LbL) deposition technique was used to prepare composite thin films of silver nanoparticles and polyaniline. The multilayer composite thin films were constructed by alternate deposition of anionic and cationic polyelectrolytes. Anionic polyelectrolyte was prepared by chemical reduction of silver ion using water soluble polyaniline as the stabilizing agent to form anionic silver nanoparticles/polyaniline composite solution. The water soluble polyaniline was prepared by interfacial polymerization of aniline monomer in presence of poly(styrene sulfonic acid co maleic acid), (CoPSS). Silver nanoparticles stabilized with anionic water soluble polyaniline were then deposited in thin film with cationic poly(diallyldimethylammonium chloride), (PDADMAC) and characterized for their optical properties. The optical properties of thin films were measured by UV–visible spectroscopy. The surface of the films was measured by atomic force microscopy (AFM). As these films are to be used as sensor for the ammonia detection, the changes in optical properties of the films were evaluated for various ammonia concentration. A strong color shift from orange-red to yellow was visible when exposed to ammonia. These silver nanoparticles/polyaniline composite thin films displayed fast color change and could be used for ammonia sensing in industrial section.