| Gold nanomaterials have attracted widespread interest both in scientific andtechnological communities due to their unique and excellent chemical and physical properties,such as catalytic activity, bio-compatible, novel electronic, optic and magnetic properties. Thepotential utility of such nanoscale materials includes catalysis, microelectronics, biologicalsensing, cell imaging, and cardiac patches as well as photothermal therapeutic. Goldnanomaterials are providing new development options for the exploitation of newsemiconductor devices and further engineering application. The controllable synthesis ofmaterials can represent the development of Micro & nano technology in some extent. Forharnessing the full potential of gold nanomaterials, a requisite goal in the development andpreparation is the ability to controllably synthesize gold nanocrystal with well-defined andorganized growth pattern. In the dissertation, in order to achieve an efficient strategy forselective and controllable fabrication gold nanomaterials with desirable dimensionality andmorphology and better understanding the mechanism, electrodeposition and dielectrophoresison the nano-material/electrode system, systematic variation of experimental parametersaffecting aligning and orientation arrangement such as voltage, frequency and the patterns ofthe micromachined electrodes were investigated.Firstly, the gold nanocrystal was synthesized on the surface of the electrodes utilizing theintegration of electrochemical deposition and dielectrophoresis with silicon micromachiningtechniques. On the basis of finite-element modelling of the electrode system in terms of thetheory of dielectrophoresis and electromagnetism, the effect of experimental parameter andconfiguration employed in our experiments is evaluated. The continuous structure and thealignment degree of assembled nanowires mainly depend on the greater magnitude of theapplied AC electric field. And the increased values of E2have significant effect on growthpoint and orientation. Furthermore, frequency plays an important role in the growth densityand smoothness. At the low frequency, it produces a nanowire with the multiple bifurcate,because of the higher degree of collection. According to the Gouy-Chapman theory withreference to the interfacial layer effects, low frequencies resulted in a markedly the effective voltage across the electrode interface, which give rise to higher degree of assembly density inthe presence of a large FDEPat low frequencies. What is more, one obvious impact is that thegrowth rate became faster highly nonlinear in response to the increased values of E2.Through combining alteration the electrode patterns using the standard optical lithographytechniques with systematic variation of experimental parameters in the growth procedure, finecontrol of architectures, such as zero-dimensional (0-D) NPs, one-dimensional (1-D) NWs,two-dimensional (2-D) networked NWs, three-dimensional (3-D) coral-like nanostructures,and 3-D mace-like nanocrystals grown on a scaffold, can be achieved.Combining the controllable growth technique to selectively fabricate gold nanostructurewith MEMS technique, the nanoparticle/SWCNT heterojunction and 1-D goldnanowire/SWCNT heterojunction were obtained. The gold nanoparticles were selectivelydeposited to functionalized surface sites on the surface of SWCNTS and the surface-enhancedRaman scattering (SERS) spectroscopy analytical experiment is introduced. The presence ofgold nanoparticles enhanced the SERS signal 55-fold. Rhodamine B with the concentration of10-9mol/L is detected based on this novel gold nanostructure substrate. The substrate isproved to create striking Raman enhanced effect. Electronic properties of heterojunctionsbetween gold and SWCNT are investigated. It was found that the heterojunction exhibitedasymmetric and rectifying I–V characteristics and the rectifying behavior can be naturallyinterpreted in terms of Schottky barriers. Subsequently, the channel current on–of ratio of1-D heterojunction is bout 106. |
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