Dimensionality-Driven Graphene Nanomaterials for Optical Identity Encoding and Lithium Battery Interfaces

Wu, Fangling and Young, Robert (2026) Dimensionality-Driven Graphene Nanomaterials for Optical Identity Encoding and Lithium Battery Interfaces. PhD thesis, Lancaster University.

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Abstract

This thesis investigates how dimensionality in graphene-based nanomaterials—from zero-dimensional graphene quantum dots (GQDs) to two-dimensional graphene–MoS₂ heterostructures and bulk highly oriented pyrolytic graphite (HOPG)—influences their optical and interfacial properties. The research follows two main directions: the development of optical physically unclonable functions (PUFs) for secure identity encoding, and the study of solid–electrolyte interphase (SEI) formation in lithium-ion batteries. For optical security, electrospray-deposited, biomass-derived GQDs produced high-entropy, excitation-dependent fluorescence patterns. These were digitally encoded using local binary pattern algorithms, demonstrating strong randomness and reproducibility for stochastic PUFs. In contrast, deterministic optical fingerprints were achieved in graphene–MoS₂ heterostructures, where photoluminescence (PL) variations across the flake were driven by stacking order and interlayer strain. Low-temperature PL confirmed the spatial and thermal stability of these emission patterns. In the energy storage study, operando Raman spectroscopy was used to examine SEI formation on surface-treated HOPG in EC/DMC- and DX-based electrolytes with varying salt concentrations. The results revealed that SEI formation precedes lithium intercalation and is strongly influenced by solvation structure, which shifts with solvent type and salt concentration. Edge-plane reactivity, solvation-driven decomposition, and SEI growth mechanisms were systematically analysed. By linking dimensionality to optical entropy and interfacial chemistry, this work provides a unified framework for engineering graphene-based nanomaterials across domains. The findings offer new strategies for secure device authentication and stable battery interface design.