Microwave-assisted synthesis of catalytic silver nanoparticles by hyperpigmented tomato skins: A green approach

A sustainable approach for the green synthesis of silver nanoparticles (AgNPs) using an aqueous extract of hyperpigmented tomato (Solanum lycopersicum L) skins (HTS) was described. AgNPs characterization and catalytic activity in the degradation of methylene blue were reported. The influence of some experimental parameters on synthesis, such as green extract concentration, pH, microwave irradiation time, as well as stabilization time, was investigated. HTS extract was initially characterized regarding its reducing potential, Fourier Transform Infrared (FTIR) molecular fingerprinting and H-1 NMR metabolite profiling and then used as a reducing-stabilizing agent for the green synthesis of AgNPs. Furthermore, a comparative study, with chemically synthetized AgNPs, was carried out and the catalytic activity of synthesized nanoparticles in the reduction of methylene blue was studied by UV-visible spectrophotometer. Obtained AgNPs were analyzed by ultraviolet-visible spectroscopy, FTIR, scanning electron microscopy and electrochemical analyses (cyclic and anodic stripping voltammetry). In general, obtained AgNPs were spherical in shape, with a diameter ranging from 21 to 93 nm, and very stable over time. Interestingly, a red shift of the surface plasmon resonance of green nanoparticles was observed as the volume of the HTS extract increased. Lastly, an improved catalytic activity in the reduction of methylene blue was detected in the case of green synthesized nanoparticles, with respect to those conventionally produced.