Silver Molybdates with Intriguing Morphology and as a Peroxidase Mimic with High Sulfide Sensing Capacity

This report entails the syntheses of morpholgically different silver molybdates by simple manipulation of experimental conditions (concentration variation and stirred/unstirred condition) using a stoppered glass vial under mild heat (∼80 °C) treatment. We have elucidated for the first time the etching of robust hexagonal ammonium phosphomolybdate (APM) by silver nitrate (AgNO₃) in an aqueous solution. Here meticulous manipulation of the experimental condition brings about three different morphologies: nanoflower (NF), nanowire (NW), and nanorod (NR) due to different recrystallization strategies and eventually identified an efficient catalyst. Among them, the last two also exhibit high morphological stability. In identical experimental conditions, while a lower APM concentration always (stirred/unstirred) yields NRs, a higher APM concentration, owing to slow diffusion, produces NFs from an unstirred solution and NWs from a well-stirred solution. The morphology is reliant on the concentration gradient of the Ag⁺ and the facile contact of the ions while etching APM. All the three different morphologies, once obtained, remain stable and are capable of acting as a nanocatalyst. But the tuned NF morphology as expected, owing to its hierarchical structure, showed the highest catalytic efficiency toward 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation. Explicit examination of the structures, stability, growth mechanism, and catalytic activity of the morphologically different molybdates along with their comparative colorimetric properties toward TMB oxidation in the presence of H₂O₂ is reported. Insightful investigation on the catalysis was executed with the representative NF which revealed efficient sulfide sensing capability in the presence of other common interfering anions and the result is significant.