Semiconductor quantum dots (QDs) have garnered a significant amount of research effort for not only scientific advances but also a range of technological applications including bioimaging and labeling, solar energy harvesting, light-emitting diodes, and next-generation displays. In this dissertation, I report four different aspects for QDs, including syntheses, photo-switching, photocatalysis, and spectroscopy. First, controlling the particle morphology and fabrication of QDs with emission covering a wide spectral region are vital in regulating the photophysical properties and the application potential of the QDs. Accordingly, for the first time, we have synthesized pyramidal shaped CdSe-CdS core-shell QDs with high morphological uniformity and epitaxial crystallinity through a two-step shell growth method. Then we report the synthesis of CdZnSe-CdZnS core-shell alloy QDs through a Cu-catalyzed solid solution alloying strategy starting from CdSe-CdS core-shell QDs. The resulting alloy QDs exhibit emission profiles covering a wide wavelength range of 470−650 nm while maintaining high PL QYs. Second, the combination of QDs and light-responsive organic switches can generate novel photo-switchable materials for diverse applications. We established a highly reversible dynamic hybrid system by mixing dual-color emitting Mn-doped CdS-ZnS QDs with photo switchable diarylethene molecules. The emission color switching between blue and pink of the system can be induced mainly by selective quenching/recovering of the Mn- PL of the QDs due to the switchable absorbance of the molecule. Third, most recently, QDs have attracted tremendous attention in the field of photocatalysis, owing to their superior optoelectronic properties for photocatalytic reactions. Herein, we demonstrate a series of stereoselective C-C oxidative homocoupling reactions of α-aryl ketonitriles using the zwitterionic-capped CsPbBr3 perovskite QDs under the illumination of visible light. Fourth, reliable quantification of the optical properties of QDs is critical for their photochemical, physical, and biological applications. We experimentally quantify the photon scattering, absorption, and on-resonance-fluorescence activities of CdSe-CdS QDs as a function of the shell sizes and geometries. Effects of shell size and geometry on optical properties for both of cores and shells are discussed.
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Citation
Yuan, Yucheng,
"Quantum Dots (QDs): Syntheses, Photo-Switching, Photocatalysis, and Spectroscopy"
(2020).
Chemistry Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.26300/9hb5-d322
