Grant: Research Tools and Instruments - Category 1 (<$150,000)

When their physical dimensions are reduced to the nanometer scale, materials assume size-dependent properties that are remarkably different from those of the bulk substance (1 nanometer = 1 billionth of a meter). For example, nanoscale crystals of some materials can be made to emit light in the near infrared (NIR) region of the electromagnetic spectrum. This wavelength range is particularly useful for medical imaging and telecommunications applications, which require light to penetrate efficiently through biological tissue and along glass fibres. The wavelength of emission may be selected fairly precisely by making the crystals larger or smaller: larger crystals give longer emission wavelengths, while smaller crystals give shorter ones. The sizes of the crystals are in turn dependent on the synthetic protocols used to make them, and much trial and error is involved in the process of uncovering reliable and reproducible methods to give high quality, brightly emitting, nanocrystals of programmable size. In order to develop these methods more rationally, we propose to uncover the mechanisms by which the nanocrystals grow, and to use this knowledge to inform next-generation synthetic protocols. We will accomplish this using the requested NIR-capable stopped-flow spectrophotometer. This instrument rapidly and efficiently mixes the reactive molecular precursors to the nanocrystals, and then follows the formation and growth of these nanocrystals by monitoring changes in the colour of the reaction mixture in terms of both absorbed and emitted light. This allows us to determine the kinetics, or rate, of growth and, by modeling these data, to determine the mechanisms by which the crystals form and grow. We will also use the stopped-flow instrument as a tool for rapid discovery of synthetic protocols by semi-quantitative, iterative improvement methods. In these ways, we hope to be able to control with high precision the size, size distribution, and possibly also shape of important NIR-emitting nanomaterials with significant high-tech applications.