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Title: Fabrication of novel nanostructures for plasmonic fluorescence enhancements and biosensing applications
Author: Price, Daniel
ISNI:       0000 0004 7658 1518
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2018
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Nanotechnology has moved fabrication of devices into smaller dimensions opening interesting and novel avenues to existing materials science. Once in the nano-regime structures are not solely defined by the classic models but start to enter the quantum domain. One such phenomena that arises is the introduction of plasmon resonance of metallic nanostructures and film surfaces. The field of fluorescence imaging is rapidly expanding due to the plasmonic properties of metallic nanostructures. This is because they enhance the fluorescence intensity of nearby fluorophores known as metal enhanced fluorescence (MEF). There has been much recent research of near-field (light propagated/detected closer than one wavelength in distance to the surface) fluorescence in the presence of metallic nanoparticles. A literature review of current novel nanostructures and those showing high MEF is given whilst considering fabrication. Often with publications showing great enhancements, up scalability, reproducibility and cost are not considered. A review of MEF used in biosensing and biological settings to show viability of this research to real life applications is also given. Colloidal lithography is chosen as a viable cheap fabrication method for depositing monolayers of hexagonally closed packed (HCP) polystyrene (PS) masks. PS 'fished' from a water surface, assembled on Si wafers, and vertical dip-coating were chosen as the lithography techniques. Gold and SiO2 were deposited by physical vapour deposition methods to create films and nanotriangle arrays through the masks. By altering the mask morphology, changing pH during deposition or oxygen plasma, and PS size, the plasmonic resonance can be tuned. Nanotriangle arrays alone and coupled with a gold-film spaced with SiO2 films were fabricated and characterised for MEF. Trilayer nanotriangle arrays with Au-SiO2-Au layering were produced, as were arrays with HCP gold nanoparticle arrays already lain. Maximum enhancements factors found for nanotriangle arrays and film-coupled nanotriangle arrays were 45X and 371X respectively.
Supervisor: Riley, Jason D. ; Xie, Fang Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral