Biosynthesis, characterization, and evaluation of antibacterial and photocatalytic dye degradation activities of silver nanoparticles biosynthesized by Chlorella sorokiniana

Nanoparticle synthesis by physiochemical methods is highly expensive and uses hazardous chemicals, and leaves behind toxic by-products. Thus, green or biological synthesis has emerged as an alternative for the same. The present study reports the synthesis of silver nanoparticles (SNPs) using Chlorella sorokiniana microalgae extract. The influence of certain parameters (pH, cell disruption methods, temperature, extract to precursor metal salt solution ratio, salt strength, biomass concentration, and incubation conditions) on SNP synthesis was studied. A strong surface plasmon response band occurred with a maximum between 400 and 440 nm at different physiochemical parameters tested. Synthesized SNPs were spherical and were 79 nm in size with a zeta potential of - 23.7 mV at optimized conditions. XRD analysis confirmed the crystalline structure of nanoparticles. The synthesized SNPs were found to be an effective bactericide, with zones of inhibition up to 20 +/- 1 and 15 +/- 1 mm for E. coli and S. aureus, respectively. SNPs were observed to catalyze the degradation of crystal violet by 97.04%, followed by methylene blue (95.75%) and eosin Y (94.9%), and the least efficiency was observed for rhodamine B (56.05%), at the end of 18 h under direct exposure to sunlight. Thus, the study concludes that SNPs synthesized using Chlorella sorokiniana are potent antibacterial agents and catalysts for photocatalytic dye degradation.