Green gold nanoparticle modified anthocyanin-based carbon paste electrode for voltammetric determination of heavy metals

Present communication reports a completely green and inexpensive method for synthesis of gold nanoparticles and their novel application in fabrication of gold nanoparticle modified anthocyanin-based carbon paste electrode for heavy metal estimation. Phytochemicals in black rice extract served as building blocks for gold nanoparticles. The conditions for gold nanoparticle preparation from black rice extract were optimized using ultraviolet–visible data. The characterization of the nanoparticles prepared was done using X-ray diffraction and atomic force microscopy techniques. The nanoparticles prepared were found to be in the range 31–52 nm and spherical in morphology. The fabricated metal sensor was used for the determination of lead, cadmium and copper using square-wave anodic stripping voltammetry. Various electrochemical parameters such as amount of modifier, supporting electrolyte, accumulation time and accumulation potential were optimized in terms of current response. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the fabricated sensor. Linear calibration curves were obtained in the concentration range of 50–500 μg L^-1 for lead and 200–700 μg L^-1 for cadmium and copper. The modified sensor showed enhanced sensitivity for electrochemical estimation of lead, cadmium and copper with low limits of detection 9.178, 86.327 and 85.373 μg L^-1, respectively.

Keywords
Gold; Nanoparticles; Green synthesis; Black rice; Carbon paste electrode; Voltammetry