Photochemical Sciences Ph.D. Dissertations

Zero-dimensional and two-dimensional colloidal nanomaterials and their photophysics

Date of Award

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Liangfeng Sun (Advisor)

Second Advisor

Mikhail Zamkov (Committee Member)

Third Advisor

H. Peter Lu (Committee Member)

Fourth Advisor

Anita Simic (Other)

Abstract

Two-dimensional oriented attachment has been confirmed as the growth mechanism of PbS nanosheets by Horst Weller in 2010. By interrupting the growth of PbS nanosheets, we investigated the intermediate PbS products which include isolated PbS quantum dots, attached PbS quantum dots and porous PbS nanosheets. We linked the intermediate PbS products with their structure and optical properties by comparing the emissions from PbS quantum dots and emissions from PbS nanosheets. Meanwhile, we shield PbS nanosheets with a shell of CdS by cation exchange to improve their optical properties and tune their bandgaps. Furthermore, we found that PbS nanosheets can be completely converted into CdS nanosheets by cation exchange, while keeping the same morphology. Thus, we can compare their photophysics properties when they have the same quantum confinement dimensions. On the other hand, carbon nanodots have become a very promising nanomaterial for numerous bio-and optoelectronic applications since they have superior chemical stability and low toxicity compared to conventional inorganic semiconductor quantum dots. We investigated the origin of photoluminescence(PL) on citric-acid-derived carbon nanodots, particularly focusing on the excitation-dependent PL behavior. By conducting the absorption, PL and PL-excitation spectra, we succeed to observe the multi-emissive states of carbon nanodots.

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