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Development of impedance-transduced chemiresistors for highly selective electrochemical detection in aqueous media

University of British Columbia

In this research, the application of electrochemical impedance spectroscopy (EIS) for electrochemical detection of different components in aqueous media (water, KCl solution, and standard electrolyte solutions) is scrutinized. One of the main advantages of electrochemical sensors compared to other electrical- or optical-based sensing methods is the real-time determination for in situ monitoring of various compounds in a medium. In this regard, 3 chemiresistors with different functional layers (i.e., graphene/poly (methyl methacrylate), polypyrrole, and polyaniline) have been developed in this research. These sensing layers have been exposed to several analytes of interest (e.g., volatile organic compounds, hydrogen sulfide, ammonia, metal ions, etc.). The experiments and measurements were conducted in a broad range of concentrations (part per billion (ppb) to part per thousand (ppt)). In all experiments, the variation in impedance provides several vital characteristics enabling the detection of the analyte of interest with much more selectively as compared to other conventional resistance-based sensors. For this purpose, the faradaic and non-faradaic responses to each analyte at different concentrations are correlated with an equivalent circuit. One of the novelties of this research is the incorporation of the individual equivalent circuit elements as features in 2D and 3D clustered plots to represent the selectivity of the sensors. Another novelty of this work relates to the use of potentiodynamic electrochemical impedance spectroscopy (PDEIS) for a selective in situ recognition of biological trace elements. PDEIS provides a combination of the information that conventional cyclic voltammetry (CV) and EIS represent for analyzing the sensing platform and the electrochemical reactions occurring at the surface of the electrode and electrolyte. Similar to the tests conducted with single analytes, mixtures of different analytes (hydrogen sulfide and ammonia at ppm- and ppb-levels) were also studied in terms of the effect of their reaction on the sensing platform. The results from the principal component analysis (PCA) for the mixtures of the analytes again confirm the high potential of the sensors and electrochemical analysis techniques (EIS and PDEIS) in selectively detecting the analytes of interest in mixture solutions.

Text

2020-09-08

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/75903

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/