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Synthesis Of Nanomaterials And Their Applications In The Electrochemical Sensors And Lithium Ion Batteries

Posted on:2012-01-08Degree:DoctorType:Dissertation
Country:ChinaCandidate:L M LiFull Text:PDF
GTID:1111330371963323Subject:Condensed matter physics
Abstract/Summary:PDF Full Text Request
Recently, given the increasing threats to the world's collective energy security, environment, biological security and et al., more attention has been focused towards addressing these critical challenges and driving global research to develop new technology and devices for energy storage and conservation, environmental monitoring, high performance sensitive sensors, and so on. Owing to their dimensions in the range of 100 nm and high surface-to-volume ratios, nanomaterials display special structures and unique interesting physical and chemical properties. The demand for high performance devices and efficient technology has led to increasing attention in advanced functional nanosized materials. The advances in nanotechnology and nanomaterials offer new directions in the design and development of electronic devices, sensors, lithium ion batteries, environmental monitoring, and so on. In this dissertation, pursuing these efforts towards improving the performance of nanomaterials on the applications of sensors and lithium ion batteries, we have explored the feasibility to design and optimize the nanostructures by means of semiconductor doping, hybridization, fabrication of novel nanostructures, and so on. The main contents in this work are listed in the following:(1) In order to realize the direct electron transfer of enzyme biomoleculars due to their high electrical properties and acceptable biocompatibility, we synthesized Sb-doped SnO2 nanowires via thermal evaporation and constructed a mediator-free horseradish peroxidase-based H2O2 biosensor through the Sb-doped SnO2 nanowires used as the immobilization matrix for the enzymes in Chapter 2. In comparison with the undoped SnO2 nanowires, Sb-doped SnO2 nanowires exhibited excellent electron transfer properties for the enzymes and higher electroactivity toward H2O2. The biosensors displayed good performance along with high sensitivity, wide linear range, and long-term stability. Those can be attributed to the enhanced carrier density arising from Sb doping and biocompatible microenvironment provided by the Sb-doped SnO2 nanowires. This study demonstrated that Sb-doped SnO2 nanowires were promising platform for the construction of mediator-free biosensors and provided new further fundamental insights into the study of nanoscience and nanodevices.(2) For the development of electrochemical enzymatic biosensors, the key issues are the effective immobilization of enzymes and reversible direct electron transfer between assembly technique based on organic template has been widely used to construct various functional biocomposite films with positive and negative charges via simple preparation process to modulate the thickness, structure and composition of the films. However, for the immobilization of enzymes via LBL assembly technique, the major problem to be solved is the weak and short-term adhesion between the prior film and the substrate. It is often uncontrolled and may not be very stable during the long-term fabrication process. Therefore, covalent bonding at the interface is very important in improving the stability of pretreatment film. In Chapter 3, we reported on a simple and versatile approach to electrograft poly(N-mercaptoethyl acrylamide) film on the glassy carbon electrode for the strongly attachment of Au nanoparticles and immobilization of HRP enzymes. The biosensors based on HRP immobilized in the Au/poly(N-mercaptoethyl acrylamide) composite film showed an excellent electrocatalytic activity toward the reduction of hydrogen oxide and long-term stability owing to the stable electrografting film and biocompatible Au nanoparticles. Our results demonstrate that the combination of electrografting and Au nanoparticles provides a promising platform for the immobilization of biomolecules and analysis of redox enzymes for their sensing applications.(3) For the enzymatic biosensors, there are several disadvantages, such as instability, high cost of enzymes and complicated immobilization procedure. The activity of enzymes can be easily affected by temperature, the pH value of solution, and toxic chemicals, which may introduce the deactivation of enzymes. In order to solve these problems, considerable attention has been paid to develop nonenzymatic electrodes. In Chapter 4, we synthesized MnO2/graphene oxide nanocomposite via a simple in situ deposition approach to construct the nonenzymatic hydrogen peroxide biosensor. The biosensors based on this novel composite exhibited a remarkable electrocatalytic activity for the detection of H2O2. The nonenzymatic biosensors displayed good performance along with low working potential, high sensitivity, low detection limit, and long-term stability, which can be attributed to the high surface area of graphene oxide providing for the deposition of MnO2 nanoparticles. These results demonstrate that this new nanocomposite with high surface area and electrocatalytic activity offers great promise for new class of nanostructured electrode in the applications of nonenzymatic biosensor.(4) Graphene has valuable applications in electrochemical biosensors due to large specific surface area, excellent electrical conductivity, ease of functionalization. Hybridization of graphene with functional nanomaterials usually enhances the attributes of each component, as reflected in electrical and chemical properties. In Chapter 5 we proposed a strategy to electro-codeposite the composite of Prussian blue (PB) particles and water-soluble graphene sheets on the glassy carbon electrode surface and further investigated their applications in electrocatalysis and biosensing applications. The expereimental results demonstrated that the PB/graphene composite modified electrode had high catalytic activity for the electrochemical reduction of hydrogen peroxide at low potential. The biosensor exhibited wide linear range, high sensitivity, fast response, and low detection limit.(5) In order to alleviate the pulverization problem and improve cyclability of metal oxide nanostructures as anode materials for lithium ion batteries, one commonly used approach is to design the electrode materials with hollow or porous nanostructures, which are an effective and promising strategy where the local empty space can accommodate the large volume change simultaneously retain its high capacity. In Chapter 6, we synthesized porous SnO2 nanotubes by electrospinning method and investigated their properties as anode materials for lithium ion batteries, which exhibited excellent cyclability. The nanotube electrode delivered a high discharge capacity of 807 mAh g-1 after 50 cycles. Even after cycled at high rates, the electrode still retained a high fraction of its theoretical capacity.
Keywords/Search Tags:Nanomaterial, Electrochemical biosensors, Lithium ion batteries, Graphene, Metal oxide
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