Alga‐mediated facile green synthesis of silver nanoparticles: Photophysical, catalytic and antibacterial activity

Abstract

A facile, convenient and green method has been employed for the synthesis of silver nanoparticles (AgNPs) using dried biomass of a green alga, Chlorella ellipsoidea . The phytochemicals from the alga, as a mild and non‐toxic source, are believed to serve as both reducing and stabilizing agents. The formation of silver nanoparticles was confirmed from the appearance of a surface plasmon resonance band at 436 nm and energy dispersive X‐ray spectroscopy. The transmission electron microscopy images showed the nanoparticles to be nearly spherical in shape with different sizes. A dynamic light scattering study revealed the average particle size to be 220.8 ± 31.3 nm. Fourier transform infrared spectroscopy revealed the occurrence of alga‐derived phytochemicals attached to the outer surface of biogenically accessed silver nanoparticles. The powder X‐ray diffraction study revealed the face‐centred cubic crystalline structure of the nanoparticles. The as‐synthesized biomatrix‐loaded AgNPs exhibited a high photocatalytic activity for the degradation of the hazardous pollutant dyes methylene blue and methyl orange. The catalytic efficiency was sustained even after three reduction cycles. A kinetic study indicated the degradation rates to be pseudo‐first order with the degradation rate being 4.72 × 10 −2 min −1 for methylene blue and 3.24 × 10 −2 min −1 for methyl orange. The AgNPs also exhibited significant antibacterial activity against four selected pathogenic bacterial strains.