H2S gasochromic effect of mixed ammonium salts of phosphomolybdate nanoparticles synthesized by microwave assisted technique

Abstract

In the present paper, new H2S gasochromic nanomaterial of mixed silver nickel ammonium phosphomolybdate synthesized by microwave assisted technique is reported. The microwave treatment was performed in the solid phase using urea and ammonium nitrate as the promoter and oxidizer agents. The designed process allows rapid synthesis of large amounts of this product in nanosized particulate morphology. Morphological and structural features of the prepared products were studied in detail. Chemical analyses indicated a stoichiometry of (NH4)0.5Ni0.75AgPMo12O40·4H2O revealing a Keggin-type framework with substitution of silver and nickel cations in its secondary structure. A home-made set-up was used to test gasochromic effect via monitoring light intensity variations passing through the samples based on their color change during exposure to different H2S gas concentrations. Response in coloration was obtained about 12% to 61.8% for concentrations from 8.5 to 100mgL−1. It is suggested that the presence of Ag and Ni ions (especially silver as counter cations) in the secondary structure of a Keggin ion plays an important role in the coloration effect of the substituted phosphomolybdate compared with the un-substituted one. In fact, color centers can be originated from the interaction of these cations of the phophomolybdate network with thiol functional group of H2S molecules.