Spherical Silver Nanoparticles Located on Reduced Graphene Oxide Nanocomposites as Sensitive Electrochemical Sensors for Detection of L-Cysteine

A new, simple, and effective one-step reduction method was applied to prepare a nanocomposite with spherical polycrystalline silver nanoparticles attached to the surface of reduced graphene oxide (Ag@rGO) at room temperature. Equipment such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) was used to characterize the morphology and composition of the Ag@rGO nanocomposite. A novel electrochemical sensor for detecting L-cysteine was proposed based on fixing Ag@rGO onto a glassy carbon electrode. The electrocatalytic behavior of the sensor was studied via cyclic voltammetry and amperometry. The results indicate that due to the synergistic effect of graphene with a large surface area, abundant active sites, and silver nanoparticles with good conductivity and high catalytic activity, Ag@rGO nanocomposites exhibit significant electrocatalytic activity toward L-cysteine. Under optimal conditions, the constructed Ag@rGO electrochemical sensor has a wide detection range of 0.1–470 μM for L-cysteine, low detection limit of 0.057 μM, and high sensitivity of 215.36 nA M−1cm−2. In addition, the modified electrode exhibits good anti-interference, reproducibility, and stability.