Date of Award
2007
Degree Type
Thesis
Degree Name
Doctor of Philosophy
Program
Chemistry
Supervisor
Dr. Zhifeng Ding
Abstract
Scanning electrochemical microscopy (SECM) is a novel surface analysis technique which can exhibit local chemical information at a sub-micron scale. SECM has been applied in many fields, such as determination of electron transfer and ion transfer at liquid/solid, reactivity/conductivity, or liquid/liquid interfaces, imaging of surface surface fabrication or modification, etc. Therefore, improvements of the SECM technique should be beneficial to many research areas. For the first time, a new SECM has been built with a 3D closed-loop positioning system. Its operation parameters were optimized by testing several samples with known surface structures, such as Pt and Au interdigitated electrode arrays (IDEAs), printed letters on transparency, and AFM calibration sample with small structures. The results are very close to the data from optical/AFM images obtained on commercial structures. The SECM probes, ultramicroelectrodes (UMEs), are one of the most important part in SECM, because they determine the lateral resolution. The fabrication procedure is optimized to obtain high quality UMEs. Different materials, such as Pt, Au, Ag and carbon fiber, with different diameters are used in the UME fabrication. Nanoelectrodes for SECM are also fabricated successfully. The homemade SECM has been successfully applied to several research areas. It has been applied for studying the grain boundary structures and localized reaction activity on the surfaces of grade 2 (Ti-2), grade 7 (Ti-7) and grade 12 (Ti-12) titanium alloys which are the candidates for package materials of nuclear waste. The grain boundary structures are imaged using SECM with ferrocenemethanol (Fc) as the redox media for the first time. Localized reactivities are studied by probe approach curves at different potentials, and their apparent rate constants are obtained by using COMSOL Multiphysics software (Version 3.3) based on finite element analysis. The contributions of doping elements, such as Pd, Ni, Mo, and impurities (Fe) to the localized reactivity are discussed. The results from different techniques, such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX), electrochemical atomic force microscopy (AFM), supported the conclusions from SECM results. The results are highly relevant for iii establishing a model to predict the survival lifetime of the package materials in the nuclear waste repository position. The corrosion behavior of non-stoichiometric UO2.002, spent nuclear waste, were investigated using SECM. Different corrosion rates on the surfaces their materials were discovered, and the mechanism was discussed. This information is very useful in determining the UO2 chemical dissolution mechanism, and its impact on groundwater and the biosphere. The cadmium (Cd) effects on photosynthesis and stomatal development of Brassica Juncea L. are studied at a single stomatal level using SECM. Cd-treated plants release less O2 than the control ones. Cd causes less stomatal density and larger size of stomatal structures. The stomata structures, density, and O2 concentration on the plants exposed with different Cd concentration are very similar, indicating that Cd concentration does not affect the stomatal development
Recommended Citation
Zhu, Renkang, "DEVELOPMENT AND APPLICATIONS OF SCANNING ELECTROCHEMICAL MICROSCOPY (SECM)" (2007). Digitized Theses. 5027.
https://ir.lib.uwo.ca/digitizedtheses/5027