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Surface-Enhanced Vibrational Spectroscopies using Electrodeposited Anisotropic Gold Nanoparticles

Date

2024-07-08

Journal Title

Journal ISSN

Volume Title

Publisher

ORCID

0009-0007-0188-3625

Type

Thesis

Degree Level

Doctoral

Abstract

Electrodeposited anisotropic gold nanostructures with the morphology of daggers are produced from a plating solution of gold (III) salt and 4-methoxypyridine (MOP) on a thin film indium tin oxide (ITO) working electrode. The gold nano-daggers (AuND) were demonstrated to be suitable for dual-modality surface-sensitive vibrational spectroscopy, more specifically: surface-enhanced Raman (SERS) and surface-enhanced IR absorption (SEIRAS) spectroscopies respectively. This universally enhancing surface was used to study pyridine and MOP at its electrified interface in electrodesorption studies. Spectral analysis, in tandem with density functional theory (DFT) calculations and surface selection rules, was used to determine the orientation of the probe molecules on the AuND during the desorption process. Over a wide range of applied potentials, only the N-bonded adsorption model/vertical-on motif was identified. A novel substrate consisting of a thin film ITO modified ZnSE internal reflection element was demonstrated to be suitable for both enhanced spectroscopies in the study of a self-assembled monolayer of 4-mercaptobenzoic acid (MBA). Finally, in an effort to use electrodeposition as a tool to create better enhancing metallized substrates, the nucleation and growth characteristics of electrodeposited gold on ITO were studied. Qualitatively, Au deposition from the Au(I) precursor, formed from the spontaneous reduction of AuCl4- by 4-methoxypridine, exhibited classical nucleation and growth current transients. Although the transients did not fit known analytical expressions for nucleation and growth more specifically the Scharifker and Hills’ model, electron microscopy studies revealed that the number density of nucleation sites could be fixed in an initial potential step to large overpotentials. These centers could subsequently be grown with narrower size distributions using a potential pulsed method in a 24-hour aged MOP, AuCl4- plating solution by pinning cycles of growth to the potential coordinate where peak reduction currents are drawn for the Au(I) → Au(0).

Description

Keywords

SERS, SEIRAS, Electrochemistry, nanotechnology, polarizability tensor, transition dipole moment, DFT

Citation

Degree

Doctor of Philosophy (Ph.D.)

Department

Chemistry

Program

Chemistry

Citation

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DOI

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