Reduction of methylene blue (MB) by ammonia in micelles catalyzed by metal nanoparticles

Abstract

The increased encounter probability between ammonia and an immobilized cationic dye in non-ionic micelles demonstrates the reduction capability of ammonia while present even at ppm levels. Catalytic amounts of silver nanoparticles (∼7 nm in size) have been shown to enhance the reaction rate of the reduction reaction, explained by the strong affinity between Ag nanoparticles and the nitrogen atom of the donor ammonia molecule. Furthermore, the preferential participation of the ammonia molecule as reductant has been proven unequivocally by taking micelle-bound dye as the reagent in the presence of phenolphthalein. The proper choice of micelle, influence of different “salting-in” and “salting-out” agents, catalysis involving nanoparticles and the thermodynamic parameters of the reaction support the possible quantification process of ammonia in solution.