Date of Graduation

7-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor/Mentor

Heyes, Colin D.

Committee Member

Chen, Jingyi

Second Committee Member

Salamo, Gregory J.

Third Committee Member

Kilyanek, Stefan M.

Fourth Committee Member

Tian, Z. Ryan

Keywords

Blinking; Cation exchange; CuInS2/ZnS; Quantum dots; Super resolution imaging

Abstract

Colloidal quantum dots (QDs) have great potential in many applications such as bioimaging, light emitting diodes, solar cells and lasers. However, a great number of studies have been focused on Cd based (II-VI) and Pb (IV-VI) based materials which are not suitable for mass production. Therefore, alternative types of QD containing less toxic materials have been introduced, including CuInS2 QDs. This I-III-VI semiconductor nanocrystals also attract lots of attention due to their large Stock shift, long fluorescence lifetime and high defect tolerance, making them attractive emitters for applications in bioimaging, photovoltaics and light emitting diodes.

In the first project, we synthesized CIS/ZnS QDs using different concentration of Zn precursors. the relationships of structure, elemental composition and photophysics of the QDs were thoroughly investigated. As the concentration of Zn precursor increases up to 4 mmol the emitting centers CIS get smaller and act as dopants in zinc blende ZnS lattices. Concurrent with this transition, subpopulation blinking analysis shows a wide heterogeneity from QD to QD increased. Also, it shows that the on time blinking statistics shift from inverse power law (or multiexponential) to monoexponential behavior. We proposed a model where the different positions of CIS in ZnS is the explanation for the wide heterogeneity in blinking behavior of the QDs. We anticipate these results can be contributed to the design for a large-scale production of the QDs.

In the second project, we applied fast blinking CIS/ZnS QDs as fluorescence probes in single particle localization super resolution imaging and compared the resolution of reconstructed images with those using commercial CdSe/ZnS QDs. The results show that even CIS/ZnS QDs obtained less precision in single molecule localization, the resolution in reconstructed images of f-actins was comparable with those using commercial CdSe/ZnS QDs. This project provides some useful insights to demonstrate that Cd-free and fast blinking CIS/ZnS QDs can be used as fluorescence probes for super resolution imaging.

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