Fabrication, characterization, and application of nanostructures on ta surfaces
Date
2011
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Abstract
The primary focus of this research has been to develop a simple and versatile method for the fabrication of nanopariicle arrays using a dimpled Ta (OT) template, and to explore the various applications of these nanoparticle arrays. The OT template, fabricated by Ta anodization in H2S04 + HF solutions, is composed of nanoscale, monodisperse shallow pores (dimples) having a diameter that is dependent on the anodization voltage. By the careful investigation of the Ta anodization process, it was found that Ta2O5 nanotubes form on the Ta surface during the first moments of anodization. These tubes later detach , exposing the substrate, which is then seen to be decorated with dimple-like structures. The detachment of the nanotubes was attributed to the gradual build-up of TaF 5 at the Ta/Ta2O5 interface . By optimizing the electrochemical conditions, stable Ta2O 5 nanotubes and free-standing membranes were produced. By sputter-coating the OT surface w ith a thin film of Au, and using the solid-state thin-film dewetting technique, the nanoscale dimples were filled with Au, forming a Au nanoparticle array. This technique of nanoparticle array formation is very sensitive to metal film thickness, with the optimum thickness being 3-4 nm. Binary alloy nanoparticle arrays were also fabricated by the thermal annealing of sequentially sputter-deposited metallic layers on the OT substrate. The electrochemistry of OT-supported Au films and nanoparticle arrays was investigated in 0.5 M H2SO4 so lution by cyclic voltammetry. It was found that the presence of a semiconducting Ta oxide film on top of the OT substrate does not affect the electrochemical response of the Au deposited on the OT surface, indicating the negligible resistance of the Ta oxide interlayer. The cyclic voltammetry investigations reproducibly showed that there is a decrease in the Au surface area after thermal annealing, as expected, due to the formation of the nanoparticle array. In a solution containing the Fe2+/Fe3+ redox couple, the OT-supported Au nano particle array behaved like a nanoelectrode array at very high scan rates. This indicates that thin-film dewetting resulted in nanoparticles that are physically separated from each other. The array was also tested for its amperometric response to glucose oxidation, using a coating of the enzyme glucose oxidase (GOx), giving a three times larger response (current density) compared to what is obtained with a conventional Au film supported on OT.
Description
Bibliography: p. 144-167.
Many pages are in colour.
Many pages are in colour.
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Citation
El-Sayed, H. A. (2011). Fabrication, characterization, and application of nanostructures on ta surfaces (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/4212