| Summary: | Hollow gold nanospheres (HGNs) demonstrate a tunable localised surface plasmon resonance ranged from the visible to near infrared (NIR) which is of significant importance for bioimaging due to the better penetration depth and reduced autofluorescence. They consist of high quality nanoshells with a small size and spherical shape. However, the reproducibility of the synthesis is an issue especially for HGNs with localised surface plasmon resonances (LSPRs) in the NIR region. Also the optical properties of these nanostructures are not yet well understood. In this thesis, the improved synthesis of hollow gold nanospheres (HGNs), which extends their localised surface plasmon resonances up to 1320 nm with citrate covered surface, is demonstrated. Their optical properties are systematically interrogated and compared to citrate-reduced gold and silver nanoparticles with similar physical properties. The scattering properties are shown through the investigation of surface enhanced Raman scatt ering (SERS) responses and the absorption properties are illustrated by a study of their photothermal properties. The comparison results show that HGNs make superior substrates over standard solid nanoparticle substrates for SERS and photothermal applications in the NIR region and the detailed synthesis can be used to tune the LSPR to the required position allowing their activity to be maximized. A new nanostructure based on HGNs is also developed and the relationship between nanostructures and SERS activities is demonstrated by correlation of Raman maps and scanning electron microscopy (SEM). Finally, the combination of SERS and spatially offset Raman spectroscopy is used to demonstrate the potential in vivo applications by showing the successful detection of bisphosphonate functionalised SERS-active nanotags through 20 mm thick porcine muscle tissue. The work in this thesis not only provides insights into the interesting optical properties of hollow gold nanospheres, but also adds to the growing body of evidence in relation to nanostructures and surface enhancement of Raman scattering and shows the promising future of applications of surface enhanced spatially offset Raman spectroscopy.
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