The Study Of The Preparation Of Graphene-metal Nano-composite Modified Electrode And Their Electrochimcal Performance

Graphene is a single-atom-thick sheet of sp2 hybridized carbon atoms that are packed in a hexagonal honeycomb crystalline structure. Graphene has attracted increasing interests from the fundamental standpoint as well as for practical applications due to its outstanding electronic, electrochemical, and thermal properties. The unique properties of graphene, such as high surface area-to-volume ratio, fast electron transferring rate and good biocompatibility, suggest that it has the ability to be incorporated in a wide array of applications, including building composites, electronics, new energy and medical therapeutics. In this paper, graphene, mesoporous Mn O2, gold nanorods and silver nano clusters had been synthetized. Some electrochemical sensor were proposed for detection of H2O2 and organophosphorus pesticide residues based on graphene-metal nanocomposites modified glassy carbon electrode. Therefore, this paper focuses on the followings:(1) A novel non-enzymatic hydrogen peroxide sensor was proposed based on graphene and mesoporous manganese dioxide composite modified glassy carbon electrode(GCE). The graphene and mesoporous Mn O2 were synthetized by modified Hummer method and hydrothermal synthesis method, respectively,and characterized by high-resolution transmission electron microscope(HRTEM) and scanning electron microscope(SEM). The non-enzymatic H2O2 sensor exhibits good performance in terms of the electrocatalytic oxidation of H2O2 at 0.7 V potential; a sensor constructed from such an electrode shows a good linear dependence on H2O2 concentration in the range of 5 μM to 3 m M with a sensitivity of 408.86 μA m M–1 cm–2. The detection limit is estimated to be 7.03 ′ 10–7 M(S/N = 3). Furthermore, the non-enzymatic H2O2 sensor exhibits freedom of interference from other co-existing electroactive species and expectant determination consequence of H2O2 in one kind of commercially available milk samples.(2) A non-enzymatic H2O2 sensor was proposed based on graphene and gold nanorods(GR-Au NRs) composite modified glassy carbon electrode(GCE). Au NRs were synthesized by seed-mediated growth method, and characterized by ultraviolet-visible spectroscopy(UV–vis) and transmission electron microscope(TEM). The GR–Au NRs composite material is endowed with a large electrochemical surface area and fast electron transfer properties in redox species. A GR–Au NRs composite modified electrode exhibits good performance in terms of the electrocatalytic reduction of H2O2; a sensor constructed from such an electrode shows a good linear dependence on H2O2 concentration in the range of 30 mM to 5 Mm with a sensitivity of 389.2 μA m M–1 cm–2. The detection limit is estimated to be 10 mM. Furthermore, the GR–Au NRs modified electrode exhibits GR-Au NRs modified electrode exhibits from other electroactive species coexistence interference free.(3) An electrochemical sensing platform for detection of phoxim based immobilizing acetylcholinesterase(ACh E) on graphene(GR) and silver nanoclusters(Ag NCs) modified glassy carbon electrode. ACh E with the carboxyl chitosan crosslinked assembly to the Ag NCs-GR modified electrode for the detection of phoxim(pesticide). The Ag NCs can provide well biocompatibility and electrocatalysis. Acetylcholinesterase can interact with the phoxim pesticide due to its catalytic activity on the substrate is suppressed, to acetylthiocholine(ATCl) as the substrate, can achieve the detection of phoxim pesticide molecules. The best measured under the condition of Phoxim on enzyme activity inhibition rate and concentration in 0.2 ~ 0.25 um n M range showed a good linear relationship, detection limit of 8.1 ′ 10–11 M. The biosensor exhibited high sensitivity, stability and acceptable reproducibility.