Photobiological synthesis of noble metal nanoparticles using Hydrocotyle asiatica and application as catalyst for the photodegradation of cationic dyes

Solar light induced photo catalysis by plasmonic nanoparticles such as Au and Ag is an important field in green chemistry. In this study an environmental benign method was investigated for the rapid synthesis of colloidal Ag and AuNPs using the extract of Hydrocotyle asiatica, as a reducing and stabilizing agent under sunlight irradiation. The nanoparticles were formed in few seconds and were characterized by UV–Vis., FT-IR, TEM, EDAX, XRD, DLS and Zetasizer. The nanoparticles were stable in aqueous solution for more than 6 months. TEM analysis established that the Ag and AuNPs were predominantly spherical with average size of 21 and 8 nm, respectively. The flavonoids and glycosides from the extract of H. asiatica were proved to be responsible for the reduction and capping through FT-IR analysis. The antimicrobial studies of AgNPs showed effective inhibitory activity against the clinical strains of gram-negative and positive bacteria. The localized surface plasmon resonance of AgNPs was used for the photo-driven degradation of cationic dyes (malachite green and methylene blue). Thus, this green technique can be used for bulk production of AgNPs, and thus prepared nanoparticles may be used for removal of dyes from effluent.