Metallic nanoparticles are traditionally synthesized by wet chemical techniques, in which the chemicals used are quite often toxic and flammable. Ripe carica papaya peel is found to be a suitable source for green synthesis of silver nanoparticles. In the present work, a cost effective and environmental friendly technique for the green synthesis of silver nanoparticles from 1 mM silver nitrate (AgNO 3) solution through the extract of ripe Carica papaya peel of various concentrations (5 ml, 10 ml, 15 ml, 20 ml, 25 ml) is described. The synthesized silver nanoparticles are characterized by using the UV-vis absorption spectroscopy, FT-IR, XRD, SEM and TEM. The formation of silver nanoparticles is confirmed by surface plasmon resonance, determined by UV-vis spectra at 400-435 nm. The shift in the absorption bands and variation in the calculated optical band gaps for the various concentrations of papaya peels extracts are also observed. The FT-IR spectra reveal that an increase in the concentration of the papaya peel extract shifts the bands to higher wavelengths. The average crystallite size for various concentrations of papaya peel extract is observed from XRD spectral analysis and is found to be around 16-20 nm, which is in good agreement with the TEM analysis. The SEM analysis shows the spherical structure of the silver nanoparticles with some agglomeration for higher concentrations of papaya peel extract. The synthesized silver nanoparticles show good antibacterial activity against human pathogens such as Escherichia coli and Staphylococcus aureus and it has many medical applications.

Recently, metal nanoparticles incorporated carbon nanostructures have tremendous applications in the field of nanosensor and technologies. In the proposed work, silver nanoparticles (Ag) decorated reduced graphene oxide nanosheets (rGONS) (rGONS-Ag) are synthesized and developed for the sensitive detection of ortho-Nitrophenol (o-NP) using electrochemical techniques. The rGONS-Ag nanocomposites are synthesized through chemical reduction method. The physical and electrochemical behaviour of the synthesized rGONS-Ag nanocomposites are characterized by using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDAX), Transmission electron microscopy (TEM) and Cyclic voltammetry (CV) techniques. The X-ray diffraction analysis reveals the formation of well crystalline silver nanoparticles (AgNp’s) on the surface of rGO nanosheets with the crystallite size of about 22.775 nm. The morphological analysis reveals the formation of well distributed cubic shape AgNp’s on the surface of rGO nanosheets. The rGONS‐Ag nanocomposites modified glassy carbon electrode (GCE) shows the good electrochemical detection performance for ortho-Nitrophenol (o-NP) with the linear detection range from 2 mM to 8 mM and with the sensitivity of about 0.221 mA mM-1 cm-2.

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