Spherical nanosilver: Bio-inspired green synthesis, characterizations, and catalytic applications

Abstract

Bio-inspired green synthesis of noble metal nanocatalyst for visible light induced reductive degradation of organicpollutants is a promising strategy for water purification. This study reports a quick synthesis of spherical and stable M. charantia fruit extract supported silver nanoparticle (AgNPs) as a green catalyst and first time applied for the degradation of various industrial dyes pollutant. The bioinspired green protocol was followed for synthesis and the formulation mechanism of AgNPs was elucidated. Flavonoid worked as reducing agent and protein worked as a stabilizer during catalyst fabrication. The catalyst was characterized using TEM (spherical nanostructure with size <16 nm), FEG-SEM (spherical), EDX (Ag at 3 Kev), AFM (average roughness 4.9 nm, skewness −0.0164), XPS, XRD, UV–Vis. (SPR at 432 nm) and FTIR techniques to investigate size, morphology, elemental composition, chemical state, crystallinity, plasmonic behavior and involved functional groups. FTIR ascertained the reducing and stabilizing nature of phytocomponents of fruit extract in AgNPs synthesis.AgNPs exhibited enhanced photocatalytic activity during degradation in presence of NaBH4 at room temperature under visible-light irradiation. The degradation time and apparent rate constant (from pseudo first order) for the AgNPs@MB, AgNPs@Rh-B, AgNPs@MO and AgNPs@4-NP system were t = 8 min (K = 0.277 min−1), t = 13 min (K = 0.162 min−1), t = 7.5 min (K = 0.269 min−1) and t = 7 min (K = 0.262 min−1), respectively. A discrepancy in degradation capacity among dye can be ascribed to relatively large molecular size and formation of the surface oxide layer. Results revealed that 91% of MB was degraded by 2.0 mg catalyst with rate constant 0.277 min−1. Degraded products were evidenced by FT-IR and degradation pattern followed pseudo-first order kinetics. The blend of green synthesis, intrinsic biocompatibility, superior photocatalytic activity, stability and recyclability of AgNPs are potentially applicable for industrial wastewater treatment and environmental remediation.