Polymerized stimuli-responsive microgel hybrids of silver nanoparticles as efficient reusable catalyst for reduction reaction
Biswajit Pany, Amrito Ghosh Majumdar, Suresh Bhat, Satybrata Si, Junpei Yamanaka, Priti S. Mohanty
Abstract
We have showcased the potential of polymerized hydrogels (PGMs) with uniform-sized stimuli-responsive microgel particles as promising alternatives to prevent aggregation in solution based nanoparticle systems. In our current work, we implemented this PGM concept by embedding anionic stimuli-responsive microgels (PNIPAM-co-AAc)-silver (Ag) hybrids within a hydrogel matrix. These PGM@AgNP hybrid materials proved efficiently as reusable catalysts for efficiently reducing 4-nitrophenol (NP) to 4-aminophenol (AP) in the presence of sodium borohydride. Comparing catalytic activity, we utilized UV-VIS spectroscopy for analysis. Complete NP-to-AP reduction took 30 min with bulk Ag nanoparticles, 24 min with PNIPAM-Ag hybrid (Neutral) and 15 min with PNIPAM-co-AAc-Ag (Anionic) hybrid microgel solutions. PGM containing PNIPAM-co-AAc-Ag hybrids achieved full reduction in just 15 min, along with a 3-min induction period. For bulk Ag NP, the first-order rate constant is found to be 0.25 min −1 , for PNIPAM-Ag hybrid (Neutral), it is 0.21 min −1 and for PNIPAM-co-AAc-Ag (Anionic), it is 0.5 min −1 where as for PGM containing anionic microgel hybrids it is found to be 0.8 min −1 . In essence, our study highlights the effectiveness of PGM@AgNP materials as efficient catalysts for the reduction of 4-nitrophenol, indicating their versatile potential in various catalytic applications.