Tailored Metal Nanostructures: Beyond Plasmon Excitation

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The functionality of nanomaterials is tailored through precise synthesis of the material and control of particle surfaces. During the forthcoming grant period, my group will focus efforts on two new classes of nanostructures; 1) atomically precise clusters, and 2) nanolasers. 1) I (and several other groups) have synthesized metal particles of Ag and Au with precision refined enough to control the exact number of metal atoms and ligands. These atomically precise particles are called clusters'. For example, one of the most stable clusters realized to date is made of 25 gold atoms and 18 thiol ligands, with molecular formula Au25(SR)18. These clusters no longer behave like nanoparticles, but behave more like molecules, with HOMO-LUMO electronic transitions and display fluorescence, a property not observed for any other size of metal particles. Owing to their unique optical properties, clusters have been proposed in fields as diverse as photovoltaics (solar cells), photocatalysis, sensors and bioimaging applications like imaging cancer cells. In all of these applications, the optical properties dictate the function of the clusters. During the forthcoming grant period, we will gain a much-needed understanding of the optical properties of metal clusters. We will use the information in the design of new clusters with compositions that dictate the desired optical properties. Spectroscopy techniques will be essential in understanding the optical properties of these materials. 2) Coherent optical fields can be generated at the surface of metal nanoparticles. They can be made to act as lasers if they can couple with the surrounding medium. We recently exploited this to make the smallest nanolasers ever made, having a diameter of ~30 nm. Important questions have arisen from the initial discoveries. For example, there are fundamental questions of whether or not it is possible for nanolasers to be electrically pumped (similar to how a laser pointer works). Over most of the last decade I have developed methods for synthesizing metal nanomaterials with desired properties that have lead to new materials for electronics, photonics, lasers and nanoplasmonics, lithography for electronic chip fabrication and biomedical materials. During the coming grant period we will engineer new metal composite nanolasers and use spectroscopic techniques to follow plasmon excitation while acting as a laser, which has never been done before. This research will allow us to answer some of the fundamental questions around this emerging field and to design structures that can be used in optics and phonics. Through challenging research, group presentations, and conference attendance, HQP will gain a diverse skill set of subject expertise, critical thinking, and oral and written communication skills. HQP will become part of a global professional network of physical chemists, with strong roots in Canadian academia.