Antioxidant and catalytic applications of silver nanoparticles using Dimocarpus longan seed extract as a reducing and stabilizing agent

Abstract

In this study, a simple and environmental friendly method was developed for the synthesis of silver nanoparticles (Ag-NPs) using Dimocarpus longan seed extract as a source of reducing and stabilizing agent. The appearance of a surface plasmon resonance peak at 432nm confirmed the synthesis of silver nanoparticles (UV-visible spectroscopy). The biosynthesized Ag-NPs were face centered cubic structures (XRD) with an approximate particle size of 40nm (TEM). Optimization study revealed that 10mL of plant extract (2mM AgNO₃) at 180min of incubation resulted the optimum product synthesis. Poly-phenolic compounds were majorly involved in the reduction of silver ions into Ag-NPs (FT-IR). The catalytic activities of Ag-NPs were assessed against the photo-catalytic degradation of methylene blue and chemo catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). The results indicated that the prepared Ag-NPs have strong chemo catalytic activity with a complete reduction of 4-NP to 4-AP within 10min. Similarly, Ag-NPs displayed higher photo-catalytic activity (K=0.12) as compared to commercial Ag-NPs (K=0.003). In addition, the silver nanoparticles exhibited a promising antioxidant activity in scavenging DPPH radicals. The findings of this study conclude that the biosynthesized Ag-NPs are promising agent possessing strong catalytic and reducing properties.

Keywords: 4-Ntirophenol; Antioxidant activity; Biosynthesis; Dimocarpus longan seed; Methylene blue; Silver nanoparticle.