Comparative Study of Antioxidant and Catalytic Activity of Silver and Gold Nanoparticles Synthesized From Costus pictus Leaf Extract

Abstract

Biological synthesis of silver and gold nanoparticles using Costus pictus leaf extract (CPLE) and their potential in vitro antioxidant and catalytic activities were reported here. Formation of Costus pictus silver (CPAgNPs) and gold (CPAuNPs) nanoparticles was confirmed by UV-visible spectroscopy and their spherical shape by scanning electron microscopy. The synthesized nanoparticles gave strong signals for silver and gold in energy dispersive X-ray spectroscopy. The CPAgNPs and CPAuNPs had an average size of 46.7 and 37.2 nm, respectively, as determined by dynamic light scattering particle size analyzer. Fourier transform infrared spectroscopy (FTIR) analysis indicated involvement of amine and carbonyl groups in the formation of CPAgNPs and CPAuNPs. Thermal stability of synthesized nanoparticles was assessed by thermogravimetric analysis-differential scanning calorimetry. CPAgNPs, CPAuNPs and CPLE exhibited tremendous antioxidant activity when being assessed by various in vitro assays, and their activity was comparable to standard antioxidants. CPAgNPs, CPAuNPs and CPLE also caused degradation of dyes like methylene blue and methyl red. While CPAgNPs, CPAuNPs and CPLE caused respective 85%, 42% and 30% degradation of methylene blue, they showed less activity against methyl red. These observations signify that such green methods open up new avenues in nanobiotechnology for the synthesis of nanoparticles with extensive industrial and biomedical applications.