Hedi MaFollow

Date of Award

12-12-2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Dr. Gangli Wang

Second Advisor

Dr. Shahab Shamsi

Third Advisor

Dr. Suri Iyer

Abstract

This dissertation studies the fundamental principles and analysis applications of electrochemiluminescence (ECL) from atomically precise nanoclusters. The nanoclusters under study are composed of a metal core stabilized by a monolayer of covalently attached ligands. Chapter one describes the basics of ECL and an overview of gold nanoclusters including both fundamentals and applications. In chapter two, the kinetics of ECL generation are investigated where nanoclusters are either immobilized on the surface or free diffusing in solution. The ECL intensity-time profiles suggest that bimolecular or pseudo first order reactions limit the ECL generation immediately following the establishment of the applied potentials, while later ECL generation is governed by diffusion or mass transport displaying a Cottrell type decay over inverse square root time. Analytical equations are derived based on ECE reaction mechanism. Successful fitting to the experiments paves ways for generalized application. In chapter three, a ratiometric analysis strategy is developed based on the kinetics of charge transfer reactions. Absolute and ratiometric electrochemiluminescence signals are elucidated from single measurements for the detection of hydroxyzine and cetirizine as prototype drugs. The two compounds function as ECL coreactants to greatly enhance the near-infrared ECL from Au22(LA)12 NCs on ITO electrodes. The kinetic profiles as signals not only improve the signal/noise ratio but also offer greater resolving power to differentiate analogue species and nonspecific interference. These case studies successfully detected and identified drug compounds in the sub nanomolar physiological range and confirmed the effectiveness of point-of-care applications. The fundamental multi-point kinetics-based ratiometric concept/strategy is not limited to a specific ECL system and generalizable to other detection systems. In chapter four, the energy band gap at the nonmetallic to metallic transitions are revealed with Au133(TBBT)52, Au144(BM)60, and Au279(TBBT)84 (whereas TBBT is 4-tert-butylbenzenethiol and BM is benzyl mercaptan; abbreviated as Au133, Au144, and Au279). Electrochemical experiments resolve different energy gaps for Au133 and Au144 at room temperature, but not for Au279 which is metallic. Spectroelectrochemistry features of Au133 and Au144 are compared with ultrafast spectroscopy to demonstrate a generalizable analysis approach to correlate steady-state and transient spectrum features. Insights on the factors affecting the energy band gap and quantized double-layer capacitance will guide future studies on improving ECL and photoluminescence properties of metal nanoclusters.

DOI

https://doi.org/10.57709/32640580

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