▎ 摘　　要

In this study, we report an eco-friendly green synthesis of silver nanoparticles decorated on reduced graphene oxide (Ag-rGO) nanocomposite by using the aqueous fruit extract of Phyllanthus acidus in basic medium. The Ag-rGO nanocomposite was characterized using UV-visible spectroscopy, infrared spectroscopy, scanning electron microscopy, energy dispersive x-ray analysis, Raman spectroscopy, x-ray diffraction and transmission electron microscopy. The fruit extract of Phyllanthus acidus simultaneously reduced the silver ions as well as graphene oxide to form the nanocomposite. Apart from reduction, the extract also acts as a good stabilizing agent for the nanocomposite. Excellent catalytic activity towards oxidation of dopamine (DA) and uric acid (UA) was achieved by Ag-rGO drop casted on glassy carbon electrode (GCE). The Ag-rGO modified electrode produced almost four times higher anodic current compared to a bare GCE. Electrocatalytic oxidation of DA and UA occurred at 0.15 V and 0.27 V using differential pulse voltammetry (DPV). The calibration curves exhibited a narrow linear range from a concentration of 10-70 mu M (R-2 = 0.9896) and 10-130 mu M (R-2 = 0.9896) for DA and UA respectively with a detection limit of 1 mu M for both by DPV (S/N approximate to 3). Simultaneous detection of DA and UA was possible with well resolved oxidation peaks, since the potential difference was greater than 100 mV. The modified electrode presented a very good selectivity, stability and reproducibility towards sensing DA and UA.