Development of Plasmonic Nanostructures for Sensing, Bio-Sensing, Biomimicry, and SERS Spectroscopy Applications

Abstract

The demand for non-invasive tools and equipment in modern healthcare systems has increased due to rising healthcare needs. In Canada, this demand has resulted in two main challenges: escalating costs and lengthy wait times. To address these issues, (bio)sensing techniques have undergone advancements in terms of speed, accuracy, and accessibility with the development of point-of-care (POC) devices. POC devices, designed to be portable, user-friendly, and capable of delivering accurate results with minimal training, have the potential to revolutionize healthcare by enabling diagnostic testing in remote or resource-limited areas. Photonics-based sensors, particularly those utilizing surface plasmon resonance (SPR) phenomenon and surface-enhanced Raman scattering (SERS) technique, have emerged as powerful diagnostic tools for various diseases. Metallic nanostructures such as nanohole arrays (NHA), crossed surface relief gratings (CSRGs), and nanoparticle (NP) assemblies have demonstrated SPR generation and SERS activity with the potential integration into Raman sensors. These nanoplasmonic sensors offer versatility, portability, and the ability to detect single molecules and atomic-scale shifts. Despite recent advances, POC devices still face challenges related to standardization, quality control, assurance, and biotag reliance, hindering their widespread adoption in the modern healthcare system within remote, poor, and underserved communities. This thesis aims to develop and advance POC diagnostic sensors, specifically focusing on nanostructure based SPR and Raman sensors, from fabrication to application. This thesis focuses on enhancing the durability, functionality, and sensitivity of nanostructures such as NHAs and nano-sized gratings through composite material development, intrinsic material adaptation, and surface morphology modifications. Additionally, new nanoplasmonic structures with enhanced sensing capabilities are fabricated and presented to broaden the engineering scope of potential assemblies for sensing applications. Finite-difference time-domain (FDTD) simulations are employed to study plasmonic enhancement as the surface is modified. This research contributes to the field of SPR and Raman techniques, providing valuable insights for the development of future POC diagnostic sensors.