Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Chemistry

First Advisor's Name

Bruce R. McCord

First Advisor's Committee Title

committee chair

Second Advisor's Name

Anthony P. DeCaprio

Second Advisor's Committee Title

committee member

Third Advisor's Name

Yong Cai

Third Advisor's Committee Title

committee member

Fourth Advisor's Name

Alexander Mebel

Fourth Advisor's Committee Title

committee member

Fifth Advisor's Name

Wenzhi Li

Fifth Advisor's Committee Title

committee member

Keywords

synthetic cathinones, SERS, drug detection

Date of Defense

6-30-2023

Abstract

In the distant past, indigenous people around the horn of Africa began chewing the leaves of khat plant for relief from daily toil. This habit resulted in the discovery of a naturally occurring alkaloid with potential medical use known as cathinone and ultimately led to the development of countless synthetic cathinone analogs. However, research into their effects is lacking due to the high pace at which new analogs become available, resulting in problems for policing and health agencies. Clandestine laboratories synthesize them in numerous ways, with little concern for purity or concentration, increasing the potential for toxic effects. Therefore, there is a pressing need for a screening method that can assist authorities in detecting cathinone analogs in a rapid, reliable, sensitive, and inexpensive way. Due to its molecular specificity and sensitivity, SERS delivers an ideal and flexible platform that provides Raman scattering enhancements for use in detecting both seized and biological fluid samples.

This work describes the fabrication of Ag colloidal systems for use as SERS-enhancing substrates to detect a variety of cathinone analogs. Furthermore, by determining the effect of functional groups attached to the core synthetic cathinone, specific interactions between the analyte and metal surface can be probed. Initial work involved Density Functional Theory (DFT) calculations at B3LYP/6-311G** level to predict Raman frequencies of the studied compounds. Normal Raman measurements on dried solid residues of synthetic cathinones standards were next examined, and the resulting scaled spectra were used to ensure concordance of the DFT-predicted frequencies with experimental values. Subsequent work focused on the synthesis and optimization of Ag nanoparticles, followed by selecting aggregating agents, such as MgCl2 and KBr, that can produce high-density hot spots on the nanometallic surface. The SERS signal intensity depends on the proximity of the analyte to the surface and the local surface plasmon resonances (LSPR), the quality of the analyte adsorption and its interaction with the surface affects the overall signal enhancement.

Ultimately, this process can improve the understanding of the SERS methodology for the detection of these compounds in seized drugs, as well as aid law enforcement and first responders by providing a more specific method for rapid and sensitive on-site screening.

Identifier

FIDC011208

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