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Nanotechnology has become the focus of scientific research due to its widespread and effective use. Silver nanoparticles (AgNPs) were produced utilizing Stachys spectabilis, and their antioxidant effect and catalytic degradation of methylene blue were investigated. The structure of ss-AgNPs was clarified by spectroscopy. FTIR demonstrated the possible functional group responsible for reducing agents. The absorption at 498 nm in the UV–Vis measurement verified the nanoparticle structure. XRD measurement demonstrated the nanoparticles to be face-centered cubic crystalline structures. TEM image proved the nanoparticles as spherical, and the size was determined as 10.8 nm. The intense signals at 2.8–3.5 keV in EDX confirmed desired product. The observation of zeta potential at −12.8 mV indicated the stability of nanoparticles. The nanoparticles can degrade the methylene blue with 54% at 40 h. The antioxidant effect of extract and nanoparticles was performed by ABTS radical cation, DPPH free radical scavenging, and FRAP assay. Nanoparticles revealed excellent ABTS activity (4.42 ± 0.10) in comparison to the standard BHT (7.12 ± 0.10). ss-AgNPs may be a promising agent for the pharmacy. • Silver nanoparticles were synthesized using Stachys spectabilis leaves. • UV–Vis, FTIR, XRD, TEM, EDX were used for elucidation of nanoparticles. • Nanoparticles displayed the outstanding antioxidant activity. • Nanoparticles synthesized from this plant can be used for clean technology. • Nanoparticles could be a promising agent for pharmaceutical industry. [ABSTRACT FROM AUTHOR]

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 1H 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. • Hyperpigmented tomato skins were used for silver nanoparticles production. • Hyperpigmented tomato skin extracts were analyzed by spectroscopic and chromatographic analyses. • Reducing sugars are the major reducing components in the extracts. • Obtained silver nanoparticles were fully characterized. • Green nanoparticles showed better catalytic properties than chemically synthetized counterparts. [ABSTRACT FROM AUTHOR]