Functionalisation of hollow gold nanospheres for use as stable, red-shifted SERS nanotags in bio-imaging

• Main Author: Moreton, Samantha
• Published: University of Strathclyde 2016
• Subjects: 540
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680839

Hollow gold nanospheres (HGNs) exhibit a unique combination of properties, in particular their tunable localised surface plasmon resonance (LSPR) from the visible to near infrared (NIR), which provide great scope for their use in many biomedical applications. However, they are highly unstable to changes in their surrounding environment and have a tendency to aggregate, particularly when exposed to high salt concentrations or changes in pH which is not ideal for applications such as bio-imaging and drug delivery where stable solutions are required for efficient cellular uptake. An improved method for stabilising HGNs which simultaneously shifts the LSPR from around 700 nm to 800 nm or greater has been developed. Three different materials which are commonly used as stabilising agents; polymers, sugars and silica have been compared in order to determine the optimum stabilising agent for use with HGNs. Results showed PEG to be the most suitable stabilising agent for HGNs displaying both an increased stability to changes in salt concentration and pH as well as increased long term stability in solution. The stabilised HGNs developed were investigated as potential surface enhanced Raman scattering (SERS) substrates for the development of stable nanotags which could be used in future bio-applications. Using a newly synthesised class of chalcogenpyrylium reporter molecules SERS detection has been achieved at four different excitation wavelengths; 633 nm, 785 nm, 1064 nm, and 1280 nm. The stabilised nanotags displayed excellent stability and produced consistent, reproducible SERS spectra in varying external environments. Furthermore, their potential for use in future bio-applications has been demonstrated at 785 nm to provide a basis for future bio-imaging at longer wavelengths. This combination of improved stability, with a LSPR in the NIR region along with SERS detection at longer wavelengths demonstrates the great potential for the nanotags developed within this work to be used in applications such as biological SERS imaging and drug delivery.