Electronic Theses and Dissertations

Date

2020

Date of Award

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Committee Chair

Erno Lindner

Committee Member

Bradford Pendley

Committee Member

Tomoko Fujiwara

Committee Member

Gary Bowlin

Abstract

The response time of chemical sensors is a critical performance characteristic that may determine their utility in a variety of applications. The rate-determining step, which controls the response time, can be either mass transport or the rate of a chemical/electrochemical reaction. To optimize the response of membrane-based sensors, we developed voltammetric methods for the determination of diffusion coefficients in polymeric membranes and demonstrated the influence of water and ion transport on the short- and long-term behavior of solid contact ion-selective electrodes (SC-ISEs). SC-ISEs are multi-layer systems with a conductive polymer (CP) film sandwiched between an ion-selective membrane and a base electrode. The delamination of these layers or the build-up of water between these layers leads to sensor failure. The water layer test (WLT) is used to prove/disprove the appearance of a thin film of water between the sensing layers. However, the interpretation of the results of a WLT is controversial, and there are discrepancies between the predictions of existing theory and experimental results. A series of mathematical models were constructed to reconcile theory and practice and to guide WLT experiments.Indicator dye-loaded, hollow nanocapsules (NCs) with single nanometer porous wall can be used as extended lifetime optical pH sensing particles with millisecond response time. However, when these nanocapsules are immobilized in a supporting matrix, for a broad range of applications, the response time increased significantly. To retain the short response time and the possibility of widespread utilization of NC-based sensing, the surface of these hollow NCs were decorated with EDOT moieties, the monomer of the CP, PEDOT. The EDOT moieties on the NC surfaces allowed the covalent attachment of the NCs to the bulk and surface of PEDOT films on electrode surfaces towards the development of electrochemical and optical sensors with extremely short response times.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest

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