Exploring the behaviour of capped metal nanoparticles on metallic surfaces

Awais, Nashwa (2026). Exploring the behaviour of capped metal nanoparticles on metallic surfaces. University of Birmingham. Ph.D.

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Abstract

Thiolated gold nanoparticles are known to undergo a redistribution of their capping layer upon immobilisation onto gold substrates, leading to the disintegration of both the ligand shell and the Au core. In-depth characterisation of these systems has demonstrated that this decomposition arises from a balance between entropic and enthalpic factors, which are influenced by substrate reactivity.

This thesis explores the behaviour of mixed metal systems to investigate how variations in the substrate and nanoparticle materials affect nanoparticle stability and the resultant surface properties. Systems of Au, Ag, and Pt nanoparticles (NPs) immobilised onto complementary substrates were studied to evaluate their stability and structural evolution, with particular attention given to whether the properties of the modified surfaces reflect those of the substrate, the nanoparticle core, or new properties arising from interactions between the two metals.

The central aim of this work was to examine how the substrate material influences the stability, chemical identity, and functionality of immobilised nanoparticles, providing new insights into the design principles for nanoparticle-based surfaces. Combinations of Ag NPs on Au and Pt, Pt NPs on Au and Ag, and Au NPs on Pt and Ag were investigated using scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry.

The thesis is structured as follows: Chapter 1 introduces the foundational work on the Au NP–Au substrate system, identifies key driving forces in mixed metal combinations, and outlines the experimental techniques employed. Chapter 2 details the materials and methodologies used in the experimental work. Chapter 3 examines the modification of Au and Pt substrates with Ag NPs, characterising the resulting surfaces and their electrochemical properties. Chapter 4 explores Pt NPs immobilised onto Au and Ag substrates, while Chapter 5 focuses on Au NPs deposited onto Pt and Ag substrates. Finally, Chapter 6 summarises the findings across these configurations, discusses their implications, and identifies potential directions for future research.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):