Fabrication of plasmonic nanostructures for healthcare applications

Samardzhieva, Iliyana (2025) Fabrication of plasmonic nanostructures for healthcare applications. PhD thesis, University of Glasgow.

Abstract

This thesis investigates high-throughput injection-moulded periodic arrays for high refractive index (RI) sensitivity and biosensing applications. The recent pandemic has underscored the critical need for early sensor diagnosis for effective treatment, emphasizing the importance of accessible and efficient healthcare services. Novel biosensors, especially optical biosensors based on localized surface plasmon resonance (LSPR), are emerging as promising diagnostic tools due to their real-time, cost-effective analytical capabilities.

Despite advances, there is a gap in developing LSPR sensors that combine high sensitivity with low fabrication costs for broad applications. This research aims to address this gap by developing and optimizing LSPR sensors with enhanced sensitivity and practical usability.

The study focuses on the coupling between LSPR and surface plasmon polaritons (SPP) in periodic nanostructures on metal films under normal light incidence. This hybridization model was explored using a double gradient plasmonic array library (DGPAL), systematically transitioning from SPP to hybrid SPP-LSPR and predominantly LSPR properties. Hundreds of nanostructures with varying sizes and periodicities fabricated on a single platform, allowed comprehensive experimental studies of their plasmonic resonance.

Key methods involved advanced nanofabrication techniques, including electron beam lithography (EBL), UV-Nanoimprint Lithography (UV-NIL) and injection moulding, to create high-resolution periodic arrays. Two fabrication approaches were compared: a simplified method using "dot writing" exposure commands and an advanced method using graphic data files for optimized design. The advanced approach, employing the Raith EBPG 5200 system, demonstrated superior quality and precision.

The findings reveal that the DGPAL platform significantly improves RI sensitivity and biomolecular detection capabilities. The nanopillar arrays achieved a sensitivity of 358 nm/RIU, closely matching state-of-the-art values reported in the literature. Sensitivity increased with both diameter and interspacing of the nanostructures, suggesting potential for further optimization.

A severe condition involving organ dysfunction due to an abnormal immune response called sepsis is reliably diagnosed by the levels of IL-6. Early detection is crucial given the high mortality rate and in this context a label-free IL-6 immunosensor was developed and tested, demonstrating real-time detection with high reusability, enhancing both efficiency and affordability.

In conclusion, this research presents a cost-effective, high-performance optical biosensor platform. The developed LSPR sensors offer high sensitivity, ease of use, and low-cost hardware, making them ideal for point-of-care applications and advancing healthcare diagnostics, thereby enhancing global health outcomes.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Gadegaard, Professor Nikolaj
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85312
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 08 Jul 2025 09:43
• Last Modified: 08 Jul 2025 09:46
• Thesis DOI: 10.5525/gla.thesis.85312
• URI: https://theses.gla.ac.uk/id/eprint/85312

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