Investigating the Effects of Thermal-Opto-Mechanical Interactions on Optical Responses of Multilayer Semiconductor Nanocrystals

The objectives of this project are 1) to investigate the effects of the processing parameters for the synthesis of multilayer CdSe/CdS/ZnS nanocrystals (NCs) in a PTFE (polytetrafluoroethylene)-based microreaction system on the geometrical dimensions (size and layer thickness) of the multilayer NCs, and 2) to experimentally and numerically investigate optical characteristics of the multilayer NCs under thermomechanical loading. This project will integrate the information from materials processing, materials characterization, and numerical analysis to answer two basic questions: 1) What controls the geometrical dimensions (size and layer thickness) of multilayer CdSe/CdS/ZnS NCs which are synthesized in a microreaction system?; 2) How do the geometrical dimensions of multilayer NCs and thermal-opto-mechanical interactions influence the optical response of the multilayer NCs? Results of this work will fundamentally transform the understanding of the optical characteristics of multilayer NCs by uncovering the effects of geometrical dimensions and thermal-opto-mechanical interactions and beneficially impact the development of NC-devices and systems of high performance and reliability. Intellectual Merit: Semiconductor NCs as potential building blocks of nanophotonics and biophotonics have attracted great interest in a variety of applications. The successful applications of semiconductor NCs necessitates comprehensive understanding of the effects of geometrical dimensions and thermal-opto-mechanical interactions on the optical characteristics of multilayer semiconductor NCs. A closely coupled experimental and modeling approach will be used to accomplish this project. Specific tasks outlined in this project to achieve the objectives are: .. To continuously synthesize multilayer CdSe/CdS/ZnS NCs of different geometrical dimensions (size and layer thickness) via a PTFE-based microreaction system; .. To investigate the effects of the processing parameters, including concentration, temperature, and residence time, on the geometrical dimensions of the multilayer CdSe/CdS/ZnS NCs; .. To characterize and analyze the optical characteristics of the prepared multilayer CdSe/CdS/ZnS NCs under thermomechanical loading, including tension, compression and cyclic heating-cooling; .. To develop, parameterize, and validate numerical models that can quantitatively analyze the optical responses of NCs under thermomechanical loading, which can provide guidelines to better design NC-based devices and systems with high performance and reliability. The research results will have broad implications for understanding the mechanisms controlling the optical characteristics of multilayer semiconductor NCs, which will help design better NC-devices and systems of high performance and reliability. Broader Impacts: Both the scientific research and its integration with education activities proposed in this project have broad implications by addressing current national needs in the development of NC-based devices and systems as well as long-term educational issues. The proposed activities will have following significant broader impacts: 1) developing PTFE-based microreaction systems, which can continuously synthesize multilayer NCs of different geometrical dimensions; 2) offering better understanding of the mechanisms controlling the optical characteristics of multilayer semiconductor NCs; 3) training graduate and undergraduate students on nanomaterials and numerical modeling; 4) enhancing participation of high school students in scientific research and education through a well-designed aggressive plan; 5) educating science and engineering to K-12 students and public at large.