Title:
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New electrochemical methods for visualizing interfacial ion fluxes
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This thesis is concerned with the development of new electrochemical methods for the visualization of ion fluxes at various interfaces. These techniques allow spatially resolved visualization and quantification of ion fluxes associated with various physiochemical and biological processes aiding to understand the mechanism and kinetics of such processes along with mapping the heterogeneity of such interfaces. In the first part of this thesis, a fast an inexpensive way to fabricate a nanoscale dual carbon electrode system was introduced. These electrode systems are well suited for detection and quantification of interfacial fluxes using scanning electrochemical microscopy because of their relatively small tip size enabling close positioning to an interface, while the small inter-electrode distance leads to high sensitivity. To enhance the capability of electrochemical scanning probe microscopy to simultaneous topography and potentiometric imaging of interfaces, a new pH-scanning ion conductance microscopy probe was developed and tested as a part of this thesis. Further, a quad-barrel multifunctional electrochemical and ion conductance probe for voltammetric analysis and electrochemical imaging of interfaces was developed and characterized in this study. These probes are amenable to further functionalization thus offering opportunities for functional imaging of both conducting and insulating pristine surfaces along with the capability of assembling nanoscale electrochemical cells for high sensitivity measurements. The ability of these probes for performing single molecule electrochemical detection was also explored in this thesis. Weak acids constitute an important group of molecules transported passively across the cell membrane. Most of the weak acids upon reaching specific intracellular sites produce various pharmacological responses which are widely exploited in therapeutics. It is thus extremely timely to have available experimental methods to accurately determine their permeation rates across bilayer membranes. A new method of forming lipid bilayers at the end of a glass pipet was reported in the later part of this thesis for quantitative passive permeation visualization. An attractive feature of all the techniques described herein is that they are very well-de ned and amenable to precise modelling of mass transport/reactivity. This was accomplished in this thesis using finite element modelling.
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