Photochemical Sciences Ph.D. Dissertations

Title

Exciton Physics of Colloidal Nanostructures and Metal Oxides

Date of Award

2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Liangfeng Sun (Advisor)

Second Advisor

Irina Stakhanova (Other)

Third Advisor

Mikhail Zamkov (Committee Member)

Fourth Advisor

Peter Lu (Committee Member)

Abstract

The growth mechanism of PbSe nanorods is confirmed as one-dimensional oriented attachment and the nano-dipole is the confirmed as the driven force to align the oriented direction along (100). By tuning the length of ligand, the strength of nano-dipolar interaction can be tuned, and this will turn on/off the one-dimensional attachment. Meanwhile, acetic acid is confirmed as the trouble for the branching formation where acetic acid will affect the growth of (111) facet which will change the dipole direction which may changed from (100) to (111) or (110) direction. Beside one-dimensional material, two-dimensional materials (PbS nanosheets) also studied. Oriented attachment growth of PbS nanosheets has been confirmed and chloroalkane is used as co-solvent to initial the oriented attachment. In our further study, chlorine ions can also play a role like chloroalkane and it can form single exponential and long decay lifetime PbS nanosheets. Our post-synthesis treatment of PbS nanosheets by trioctylphosphine can enhance the photoluminescence quantum yield of PbS nanosheets from 6% to over 50%. This high quantum yield nanosheets is applied for a down-conversion LED device and a 13% quantum yield is achieved. The up-conversion properties of carbon quantum dots and the low temperature spectrum of gallium oxide with doped by titanium also been studied.

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