Application Of Electrochemically Reduced Graphene Oxide And Silver Nanoparticles In Electrochemical Sensors

Graphene and silver nanoparticles have attracted widely attention and deeply research from different fields owing to its outstanding performance of large surface area, high conductivity and excellent electrocatalytic activity. Because of its excellent properties of rapidity, accuracy, simplicity, low cost, high sensit ivity and good selectivity, the electrochemical sensor play an important role in the field of medicine, environment and food industry. In this thesis, graphene and silver nanoparticles were used to prepare three kinds of electrochemical sensors, which could be applied to the determination of small biological molecules, such as ascorbic acid, dopamine, uric acid and hydrogen peroxide. The main content was listed below:Part 1: Self-assembly of Electroche mically Reduced Graphene Oxide Modified Electrode for Simultaneous Detection of Dopamine, Ascorbic acid, and Uric acidA facile, green, and effective approach is designed to prepare the electrochemically reduced graphene oxide(ERGO) modified glassy carbon electrode(GCE) by combining electrochemical reduction method with self-assembly technology. Graphene oxide(GO) was assembled on a glassy carbon electrode by the electrostatic attraction interactions between graphene oxide and polyethyleneimine(PEI), and then the electrochemically reduced graphene oxide was obtained by the electrochemical reduction of GO. The ERGO film was characterized by scanning electron microscopy(SEM), electrochemical impedance spectroscopy(EIS), and cyclic voltammetry(C V). Due to the excellent electronic properties and large surface of ERGO, the ERGO/PEI/GC E displays excellent electrocatalytic activity toward the oxidation of dopamine(DA), ascorbic acid(AA), and uric acid(UA) by differential pulse voltammetry. The linear ranges for DA,UA, and AA are 0.5-100 μmol/L, 2-100 μmol/L, and 20-1400 μmol/L with the detection limits of 0.5 μmol/L, 1 μmol/L, and 6 μmol/L, respectively. In addition, the ERGO/PEI/GCE displays high repeatability, stability and selectivity for the determination of DA, UA, and AA, which were used to detect the practical samples with satisfactory results.Part 2: A Novel Nonenzymatic Hydrogen Pe roxide Sensor Based on Graphene and One-step synthesized of Silver Nanoparticles@poly(dopamine) Modified Glassy Carbon ElectrodeA novel non-enzymatic electrochemical biosensor for sensitive hydrogen peroxide(H2O2) detection was constructed based on the silver nanoparticles@poly(dopamine)(Ag NPs@PDA) and electrochemically reduced graphene oxide(ERGO). Here, silver nanoparticles(Ag NPs) were obtained by one-step synthesis of mixing dopamine(DA) and silver ion(Ag+) in weak alkaline aqueous solution without additional reductants or toxic reagents. The polymerization of dopamine and the reduction of Ag+ ion occurred simultaneously in the process. And graphene film was prepared by self- assembly of graphene oxide(GO) using polyethyleneimine(PEI) grafted surface of glassy carbon electrode(GCE) followed by the electrochemical reduction of GO. Ag NPs@PDA was characterized by scanning electron microscopy(SEM), UV- vis absorption spectroscopy, and electrochemical impedance spectroscopy. The Ag NPs@PDA/ERGO/PEI/GCE showed high catalytic activity toward the reduction of H2O2 due to the high surface area, good conductivity, and electrocatalytic activity of ERGO and Ag NPs. And the sensor exhibited a linear range of 0.1-16.4 mmol/L with the detection limit of 15.3 μmol/L for H2O2. In addition, the sensor also displays high selectivity, good repeatability, and long-term storage stability for the determination of H2O2. And it has been applied successfully to the detection of H2O2 in real samples.Part 3: A Nonenzymatic Hydrogen Peroxide Sensor Based on Electrodepositing Silver Nanoparticles on Electroche mically Reduced Graphene OxideA novel nonenzymatic hydrogen peroxide(H2O2) sensor was fabricated by electrodepositing silver nanoparticles(Ag NPs) on electrochemically reduced graphene oxide(ERGO). The ERGO film modified electrode was prepared by electrochemical reduction of graphene oxide(GO) assembled by 3-aminopropyltriethoxysilane(APTES) on glassy carbon electrode(GCE) through the electrostatic interaction between negatively charged GO and positively charged APTES. The prepared process of modified electrode was characterized by electrochemical impedance spectroscopy(EIS). Due to the high electrical catalytic properties of ERGO and Ag NPs, the Ag NPs/ERGO/APTES/GCE showed good catalytic activity toward the reduction of H2O2, and it exhibits three linear calibration range in the ranges of 0.01-91.55 mmol/L with the detection limits of 5 μmol/L. Meanwhile, the sensor also exhibits good stability, high sensitivity, and reproducibility.