Sub-nanometer Optical Imaging and Self-Assembly on Plasmonic Metals

点击翻译按钮获取中文摘要

My group's long-term goal is to use the capabilities of scanning probes, such as the two new state-of-the-art scanning probe microscopes described in this proposal, to address critical research questions in nanophotonics and surface chemistry/physics. In this proposal, two research questions/themes are identified and described. Theme 1: Towards atomic optical imaging with quantum optical plasmonics By combining scanning tunnelling microscopy with optical spectroscopy, it has been demonstrated that photoluminescence and also Raman images of single molecules can be acquired with sub--nanometer spatial resolution. These results dramatically illustrate how plasmonic materials can enhance optical processes and they also represent an important step towards atomic optical resolution. With theorists at Queen's, our goal is to develop and test a quantum mechanical model of the optical enhancement in photoluminescence and tip---enhanced Raman imaging that includes the opto-mechanical coupling between the vibrating molecules and the plasmon resonance. We will perform optical imaging of model systems, including molecules and atomically precise nano-clusters, using a cryogenic nano--optical microscope. Atomically sharp tips will be selected using non-contact atomic force microscopy with a qPlus sensor. The impact will be fundamental insights into plasmon enhancement that could potentially have applications for nanoscale optical devices, an important technology market in North America. Theme 2: Self--assembly of N--heterocylic carbenes on plasmonic metals Although the self--assembly of organic molecules on metallic surfaces is one of the most powerful methods for patterning at the nanometer scale, the thermal and oxidative instability of commonly used thiol-based self-assembled monolayers are significant impediments to their widespread commercial use in plasmonic optical devices. With collaborators in Chemistry, we have demonstrated that N--heterocyclic carbenes (NHCs) represent a viable alternative to thiols. Our goal is to optimize the stability of these new overlayer systems by systematically modifying the structure of the NHCs and concurrently developing a molecular--level understanding of their surface chemistry, self--assembly methods and protocols. The impact will be an optimized next generation functionalizing agent for metal surfaces based on NHCs that can be used as a surface modifier with applications in molecular electronics, microcontact printing, biosensing and surface protection. The insights gained through the study of NHC self-assembly on surfaces will also inform the synthesis of NHC-stabilized metal nanoclusters that are used in medicine and catalysis. This proposal will provide training for a total of 18 students at the following levels: 2 PhD, 6 MSc, 5 undergraduate summer students, and 5 final year honours theses.