Laser-engineered nanocomposites for sensing applications

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Surface-Enhanced Raman Scattering (SERS) is an extremely powerful optical detection platform for the development of sensitive and quantitative analytical methods suitable for real-time monitoring. This technique provides information about the vibronic 'fingerprint' of a molecule located close to plasmonic nanostructures and therefore allows for a unique classification of the type of analyte detected. This method has also been proven to have a single-molecule detection capability. SERS-based approaches have enabled a number of important applications in bioanalytical sensing, such as in vivo tumour targeting, glucose sensing at clinically relevant concentrations and microbial system analysis, and are considered a major prerequisite for progress in areas such as nanobiotechnology and personalised medicine. In spite of the apparent advantages over commonly used fluorescence-based methods, SERS is yet to be established as an analytical tool. This is, in part, due to the fact that small variations in the SERS substrate (preparation, aggregation, surface morphology, etc.) have drastic effects on the SERS performance. Therefore the stability and reproducibility issues of SERS-active substrates have to be addressed in order to facilitate its application in quantitative analysis.Current fabrication techniques of SERS substrates with moderate to high enhancement factors, and reproducible and uniform responses are dominated by e-beam lithography, nano-imprint, self-assembled nanosphere, hybrid nanoporous lithography methods, etc. These techniques are still costly and rather cumbersome for production of large area SERS substrates, hence the high price of commercially available SERS platforms. The focus of this project is to demonstrate novel SERS platforms based on laser-engineered nanocomposite systems for dramatically improved performance and fabrication control, addressing current SERS materials limitations. Tailored Ag-/Au-ion and Ag-/Au-nanoparticle doped substrates with different dopant concentrations and volume filling factors will be fabricated suitable for SERS analysis with frequently used excitation wavelengths in the spectral region from 400 to 1000 nm. A spatially selective nanocomposite annealing technique will be developed in order to realise large area planar platforms with controllable geometry and reproducible enhancement factors, allowing a step change in fabrication of robust sensing platforms for quantitative SERS analysis. Furthermore, the proposed material systems will form the building blocks of a future microfluidic sensing devices for biomedical, environmental and security applicatons.