Green Synthesis of Gold Nanoparticles for Fabrication of an Electrochemical Sensor Sensitive to Nitrophenial based on Graphene Nanoplatelets/Gold Nanoparticles

Synthesis of chemical compounds using environmentally friendly materials is the goal of green chemistry. In recent years use of planets as stable and available sources to prepare metal nanoparticles has more attention for researchers. Synthesized nanoparticles using the aim of green reagents can be used in the bio application such as fabrication of electrochemical sensors [1]. In this regard, gold nanoparticles (AuNPs) due to unique properties such as high conductivity, high surface area and electro catalytic properties recently used in the fabrication of optic and electrochemical sensors [2]. Analysis of nitrophenols in natural water resources is an important indicator to quality control of water. 4-Nitrophenol (4-NP) is one of the hazardous chemicals in contaminate list of environmental protection agenay (EPA) duo to its stability and poisonous. Respiration or eating of 4-NP in the short period causes hard headache and drowsy, nausea and dark blue skin. In addition 4-NP was reported as cancerous tratogen and tagen so its application should be under control [3]. So, monitoring of 4-NP in water resources using a sensitive and selective electrochemical sensor is highly interested. In this work, a novel method is presented for green synthesis of AuNPs using extracted E. tereticornis leaves as the reducing agent in the presence of HAuCl4 in ambient temperature. The synthesized AuNPs was mixed with graphene nanoplatelets (GNPs) under sonication to form a homogeneous nanocomposite (AuNPs/GNPs). Characterization of the nanocomposite using UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy coupled with energy dispersive spectroscopy (FESEM-EDS) showed a homogeneous distribution of AuNPs nanoparticles on GNPs sheets. Due to synergetic effect of good electrocatalytic properties as well as conductive nature of AuNPs microspheres and large surface area with high 257 conductivity of GNPs, the synthesized nanocomposite was drop casted on the surface of glassy carbon electrode and used as an electrochemical sensor (AuNPs/GNPs/GCE) for determination of 4-NP using differential pulse anodic stripping voltammetry. Under optimal conditions of phosphate buffer (0.01 M, pH 4.0), scan rate of 0.05 V/s, drop casting nanocomposite ratio (AuNPs/GNPs) of 5 (V/V), differential pulse voltammetry of 4-NP showed an oxidation peak at around 0.025 V due to exchange of 2 electrons and protons. The fabricated sensor has good potential for determination of 4-NP in lake water, reverse osmosis drink water and natural mineral water with satisfactory results.