Kinnear, Sophie L. (2015) Development and application of electrochemical scanning probe microscopy techniques for studying interfacial processes. PhD thesis, University of Warwick.

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Abstract

This thesis is concerned with the construction of new electrochemical scanning probe microscopes. Designed to support a wide variety of existing techniques as well as to develop new techniques. This
exibility was achieved by basing the equipment around a field programmable gate array card (FPGA), which allows for a software program to be configured on the physical FPGA card as hardware. This technology provides the efficiency and high speed of bespoke hardware and can be reprogrammed like software. The instrumentation was programmed in-house using the graphical programming language, LabVIEW, which allowed for changes and upgrades to be made when necessary. Two branches of projects were studied with the FPGA instrumentation, crystal dissolution and surface charge mapping. For the crystal dissolution studies, dual-barrel conductance micropipettes were used to investigate the dissolution of NaCl and calcite, with microscale spacial resolution. This technique had many advantages over traditional methods. For instance, high temporal resolution in the order of sub-milliseconds was achieved through the employment of in-house built current followers. In addition, fast mass transport inside the pipette allowed the study of surface kinetic processes. The implementation of finite element method simulations complemented the experimental findings, by enabling the quantitative analysis of the data to extract intrinsic dissolution rate constants. The technique is also complemented by atomic force microscopy, which provides an alternative method for analysing the etch pits. The same equipment is used as a scanning ion conductance microscope (SICM) to investigate the surface charge of both conductive and non-conductive surfaces. A double electric layer forms at the solid-liquid interface of a sample that is immersed in electrolyte solution, at low ionic strength the thickness of the double layer increases, which enables its detection via the SICM pipette. The formation of the double layer at the pipette walls induces ion current rectification, at the same time a surface induced rectification arises as the nanopipette approaches the substrate surface. The combination of these results in the creation of an ion perm-selective region, which results in an increase or decrease in current that is proportional to surface charge. Point measurements, maps and CVs of dynamically changing surfaces have been recorded.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Scanning electrochemical microscopy
Official Date:	September 2015
Dates:	Date Event September 2015 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Unwin, Patrick R. ; Macpherson, Julie V.
Sponsors:	European Research Council
Extent:	xviii, 177 leaves : illustrations (some colour), charts
Language:	eng

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