Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Chemistry

Program Name/Specialization

Biological and Chemical Sciences

Faculty/School

Faculty of Science

First Advisor

Dr. Vladimir Kitaev

Advisor Role

Supervisor

Abstract

The work presented in this thesis deals with developing practical plasmonic metal nanoparticle (PMNP) platforms that combine strong optical response with improved tunability and stability for sensing. Wavelength-selective photochemical growth is established as a scalable route to PMNP morphology control. By improving light delivery and thermal management, selectivity is maintained when reactions are scaled to hundreds of millilitres.  The PMNP templates are converted into compositionally tunable Ag–Au bimetallic alloy PMNPs to balance localized surface plasmon resonance (LSPR) sensitivity with improved chemical stability. Controlled gold precursor additions systematically shift the LSPR peak. Low gold addition leads to LSPR peak broadening and partial peak splitting consistent with population dispersity, while higher gold content produces convergence toward a single dominant LSPR peak, indicating more uniform alloy formation. A parallel objective of the thesis focuses on silica chemistry, since dielectric shells and silica matrices offer one of the most practical routes to stabilizing nanoparticles (NPs) without losing optical function. A mechanistic question in two phase tetraethyl orthosilicate (TEOS) delivery methods is addressed by replacing arginine with urea as the base catalyst, and the results show that urea can generate highly monodisperse silica seeds in the tens of nanometres regime with low dispersity, followed by clean regrowth to larger diameters while maintaining narrow size distributions. Building from this foundation, multiple silica coating strategies are evaluated for PMNP cores. Sodium metasilicate based deposition reliably produces thick shells but is difficult to stop at thin layers once condensation proceeds. A surface priming approach using (3-aminopropyl) triethoxysilane (APTES) followed by TEOS growth provides the strongest evidence for uniform coatings, with optimal priming giving the lowest dispersity, while excessive silane dosing introduces dispersity consistent with competing condensation pathways. Two gold coating strategies are finally explored to drive the reaction toward deposition rather than galvanic replacement. A basified Au–5,5-Dimethylhydantoin (DMH) complex reduces the availability of ionic gold, yet low gold conditions still show blue shifting consistent with pitting, while higher additions give more predictable red shifting. A cluster-based approach generates neutral Au0 clusters first and transfers them rapidly into coating reactions, producing a uniform red shift from the original silver position consistent with progressive deposition. This thesis provides scalable synthesis and coating methods that link reaction control to predictable outcomes, while addressing the main chemical limitations of silver. This supports the broader goal of creating tunable, robust plasmonic nanoparticles suitable for LSPR based sensing in complex sample environments.

Convocation Year

2026

Convocation Season

Spring

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Available for download on Sunday, April 23, 2028

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