Electrochemical biosensor based on reduced graphene oxide and Au nanoparticles entrapped in chitosan/silica sol–gel hybrid membranes for determination of dopamine and uric acid

A novel platform based on reduced graphene oxide and Au nanoparticles entrapped in chitosan/silica sol–gel hybrid membranes (RGO–AuNPs–CSHMs) was successfully constructed for the fabrication of biosensor. The hybrid membranes are prepared by cross-linking chitosan (CS) with 3-aminopropyltriethoxysilane (APTES), while the presence of RGO and AuNPs improved the conductivity of CSHMs. The morphologies and electrochemistry of the nanocomposite film were investigated by using scanning electron microscopy and electrochemical techniques including electrochemical impedance spectroscopy and cyclic voltammetry (CV), respectively. The results suggested that the modified electrode exhibited enhanced sensitivity towards the oxidation of dopamine (DA) and uric acid (UA). Well defined and separated oxidation peaks were observed by CV and differential pulse voltammetry. Linear calibration plots for the oxidation of DA and UA were obtained in the range of 1.0–200 μM for DA and 1.0–300 μM for UA. Detection limits of DA and UA were found to be 0.3–0.7 μM, respectively. In addition, the sensor was successfully applied for the determination of analytes urine samples using the standard adding method with recoveries of 94.2–106.0%.