Scanning near-field optical microscopy and spectroscopy studies of quantum dots.

The study of biological systems and processes is limited in optical microscopy by diffraction. Scanning near-field optical microscopy (SNOM) is a technique which can overcome the diffraction limit and resolve nanoscale features with light. However the intrinsic nature of the technique results in it being limited by low light intensities when based on fluorescence studies of standard organic dyes. This proposal seeks to overcome this problem by considering in-organic quantum dots. These are currently being explored in medicine because they produce a far more intense and reliable source of fluorescent emission than normal organic dyes. Quantum dots also have the ability to be tuned to emit at different wavelengths just by changing their size and hence can give specific spectral characteristics. The proposal aims to immobilise the quantum dots (made from CdSe/ZnS) in an e-beam resist and then probe them with the scanning near-field microscope. The fluorescent signature will then be analysed via developments to the SNOM instrument that will enable it to spectrally determine the nature of the fluorescent emission from the quantum dot. Via the careful preparation of the quantum dots within the e-beam resist film, spectral signatures from single quantum dots will be achieved. This project represents a stepping stone to the potential introduction of quantum dots into a biological system where they can be used together with the near-field microscope to produce enhanced images with nanoscale resolution and spectral sensitivity.