| Graphene has emerged as an exciting material because of the novel and uniquephysicochemical properties, such as high surface area, excellent conductivity, highmechanical strength and ease of functionalization, associated with itstwo-dimensional (2-D) structure. Based on its fascinating properties, graphene isused as an ideal material for electrochemical sensing and biosensing. However, tofurther expand and optimize the use of graphene in electrocatalysis, it is the utmostimportant to study the graphene based nanocomposites. The nanocompositescombing various functions of the nanomaterials and the original properties ofgraphene have showed great importance in the electrochemical sensing andbiosensing. In this thesis, several electrochemical sensors based on functionalgraphene or graphene-metal oxide hybrid were fabricated and their application inelectrochemical sensors were investigated in detail. The main contents of this thesisare as following:1. Three approaches including physical adsorption, in situ reduction, and onepot synthesis were developed to fabricate cuprous oxide-reduced graphene oxide(Cu2O-rGO) nanocomposites, These nanocomposites were used to fabricate H2O2sensors. The morphology and crystal structure of these nanocomposites werecharacterized by SEM and X-ray diffractometer (XRD). The result revealed thecomposites with different fabrication approaches have different morphologyd andcrystal structures. Electrochemical studies showed that the as prepared componentsdisplayed much enhanced performance for the catalytic reduction of H2O2than thesingle component Cu2O. Among these Cu2O-rGO nanocomposites, the productprepared through the simple physical adsorption approach displayed a slightly betterperformance than the other two composites. A wider linear range, higher sensitivityand better stability were achieved on the Cu2O-rGO based sensor than Cu2O basedsensor for accurate detection of H2O2. Our approaches provide a new and flexiblemethod to develop high performance nonenzymatic H2O2sensor.2. A ternary nanocomposite Au-MnO2-rGO composed of gold nanoparticles (AuNPs), manganese dioxide nanorods (MnO2NRs) and reduced graphene oxidenanosheet (rGO) was synthesized for the catalytic reduction and nonenzymatic sensing of hydrogen peroxide (H2O2). The morphology of the ternarynanocomposites was characterized by SEM and TEM. The component and structureof these composites were investigated by XRD It was found the integration of MnO2NRs with rGO could enhance the attachment of MnO2NRs on the electrode andimprove its conductivity. Subsequent decoration of Au NPs, although with small sizeand tiny amount, further improved the performance for the reduction of H2O2.Greatly enhanced catalysis was observed on the ternary nanocomposite due to thesynergistic interaction among MnO2NRs, rGO and AuNPs. Based on thisAu-MnO2-rGO composite, a new nonenzymatic H2O2sensor with a wide linearrange, low detection limit, high sensitivity, good stability and negligible interferencefrom ascorbic acid was successfully fabricated.3. A nitrite sensor was developed based on reduce graphene oxidefunctionalized with polydimethyl-diallyl ammonium chloride (PDDA). ThePDDA-rGO was prepared by reduction of GO with hydrazine in the presence ofPDDA. The morphology of the functionalized graphene was characterized by AFM.The addition of PDDA greatly improved the dispersity and stability of rGO in water.PDDA-rGO nanocomposites was used as a electrode material to construct a NaNO2sensor. Compared with unmodified rGO and bare glassy carbon electrode, thePDDA-rGO displayed higher current response and low oxidation potential for theoxidation of nitrite. A sensitive and selective NaNO2sensor was constructed withPDDA-rGO, whose performance is comparable or even better than many sensorsbased on noble metal or graphene involved hybrid materials. Our results indicatedthat functionlized graphene, in addition to graphene hybrid, could also provide agreat potential for constructing advanced electrochemical sensors. |
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