Development of optically bright nanotags for SERS

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Surface enhanced Raman scattering is an extremely sensitive and selective technique that is rapidly emerging as an effective method for ultrasensitive analysis. It offers an increased enhancement over normal Raman scattering therefore is ideal for the detection of trace amounts of analyte and because of the molecularly specific spectra obtained it is ideal for detecting analytes in mixtures. The sensitivity of SERS also lends itself to stand off detection due to the intense signals which can be obtained from specially synthesised labels as well as ones which are commercially available. These labels, in combination with nanoparticles, can be used as coded labels due to their unique vibrational spectra allowing labelling of products in areas such as brand protection for example in the beverage market.This project proposes to develop the technique and labels required to carry out detection of coded nanoparticles using an excitation wavelengths of 785 nm or higher. This will require synthesising different types of metal nanoparticles which have absorbances towards the infrared region of the electromagnetic nanoparticles and developing coatings for the nanoparticles that would protect them from harsh environments such as strong acid, while still being able to give a strong SERS response. We will then develop ways to make and optimise the nanoparticles to give the strongest (brightest) SERS signal possible. This may require separation procedures, for example using simple fluidics or separation systems, to separate the brightest nanoparticles from ones that are more weakly SERS active to enrich the SERS response. The nanoparticles will be cpated with, most likely, silica to allow them to remain strongly SERS active and stable to the environment in which they will act as a label. We will then use these bright, environmentally stable nanoparticles for the detection of whole bacteria in the healthcare environment.