Phyto-crystallization of silver and gold by Erigeron annuus (L.) Pers flower extract and catalytic potential of synthesized and commercial nano silver immobilized on sodium alginate hydrogel

A green, eco-friendly approach for the synthesis of silver and gold nanoparticles (AgNPs and AuNPs) using Erigeron annuus (L.) pers flower extract as both the reducing and capping agent is reported for the first time. Optimal nanoparticle production was achieved by adjusting various parameters including pH, extract concentration, metal ion concentration, and time. Initial verification of AgNP and AuNP production was done by visual observation and measuring surface plasmon spectra at 434 and 537 nm, respectively. The synthesized AgNPs and AuNPs were characterized by high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), energy dispersive spectrophotometry (EDS), Fourier transform infrared spectroscopy (FTIR) and zeta potential. The catalytic potential of E. annuus flower extract, silver ions, synthesized AgNPs, commercial grade AgNPs, and a mixture of flower extract and AgNPs immobilized on sodium alginate hydrogel beads (Na/Al HB) was analyzed. The ability of these immobilized materials to degrade methylene blue was investigated. Commercial grade AgNPs immobilized with Na/Al HB 1.5 g/20 mL were observed to have good catalytic activity followed by a mixture of synthesized AgNPs immobilized with Na/Al HB and E. annuus flower extract immobilized with Na/Al HB at 1.5 g/20 mL.