Monodispersed biodegradable microparticles with wrinkled surface coated with silver nanoparticles for catalytic degradation of organic toxins

Microfluidic fabrication of monodisperse microgels for biomedical, nanotechnological, environmental and catalytic applications has become the subject of growing interest. In this work, monodisperse polyethylene glycol diacrylate [P(EGDA)] microgel particles were fabricated using a CNC-milled microfluidic device with Lego-inspired interlocking mechanism. Silver nanoparticles (AgNPs) were synthesised and stabilised in situ on the wrinkled surface of the microgel particles using AgNO₃ as metal precursor and NaBH₄ as reductant. The loading of AgNPs (7.5 wt%) on microgel beads was confirmed by energy-dispersive X-ray spectroscopy, X-ray diffraction, and thermogravimetric analysis. Surface wrinkles were found to be a useful morphological feature acting as reservoirs for accumulation of AgNPs. Ag-P(EGDA) hybrid polymer particles were shown to be an efficient catalyst for the reduction of 4-nitrophenol (4NP) into 4-aminophenol (4AP) by sodium borohydride at room temperature. After 40 min, 0.08 M 4NP was completely converted into 4AP using 2.1 mg/mL of Ag-P(EGDA) catalytic particles and the reaction followed a pseudo first-order kinetics. The apparent rate constant increased from 0.0142 to 0.117 min^-1 when the loading of catalytic particles increased from 1.7 to 2.50 mg/mL indicating that the reduction is occurring on the catalyst surface according to Langmuir-Hinshelwood model. Ag-P(EGDA) hybrid microgel was a potent and recyclable catalyst for room-temperature degradation of methylene blue (MeB) by NaBH₄. At the Ag-P(EGDA) loading of 2.0 mg/mL, 25 µM of MeB was completely degraded in 6 min. Composite Ag-P(EGDA) microgel beads can be used as an ecofriendly and easily recoverable catalyst for the transformation of other organic pollutants into useful chemicals.