Department Chair

M. Scott Goodman

Date of Award

5-2023

Access Control

Open Access

Degree Name

Forensic Science, M.S.

Department

Chemistry Department

Advisor

Dr. Sujit Suwal

First Reader

Dr. Sujit Suwal

Second Reader

Dr. Jinseok Heo

Third Reader

Dr. Joonyeong Kim

Abstract

The use of Near-Infrared (NIR) Surface-Enhanced Raman Spectroscopy (SERS) has recently served as a strong candidate for highly sensitive bioimaging without the use of ionizing radiation and strong magnetic fields. Given the potential of heptamethine cyanine dyes to absorb in the NIR region while retaining stability and sensitivity, recent research has focused on altering the chemical moiety at the heptamethine displacing the meso-chloride to discover novel reporter molecules with enhanced SERS signaling. Such research has determined that lipoic acidcontaining N-acetyl amino tri-carbocyanine can produce a strong SERS intensity, given the affinity of sulfur for AuNPs. Such discoveries have utilized improper reporter dye aggregation. To overcome this, a citrate-capped quick-freezing induced AuNP aggregates (QFIAA) solution is used, which potentially enhances negatively charged nanoparticle surfaces to interact with the positively charged tri-carbocyanine dyes, eliminating lipoic acid-dependent AuNP interaction. To validate this hypothesis, two sets of dye molecules are synthesized, with or without lipoic acid, and the NIR-SERS intensities after QFIAA are compared. This project highlights QFIAA as a powerful method for NIR-SERS studies of tri-carbocyanine dyes with significant enhancement of signals even the dye concentrations at 5 nM. In addition, the synthetic protocols are markedly improved compared to the literature-reported methods.

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