Graduation Semester and Year

2021

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Physics and Applied Physics

Department

Physics

First Advisor

Yujie Chi

Abstract

Cu-cysteamine (Cu-Cy) is a material that has the cysteamine bonded with Cu. It is a molecular photosensitizer which can be activated by visible, ultraviolet light, and X-rays to generate reactive oxygen species (ROS). Cu-Cy has been used in various applications such as solid-state lighting, radiation detection, and as treatment of both shallow and deep cancers. Hence, it is important to study the stability, electronic and optical properties of Cu-Cy as well as finding other possible cysteamine systems. The first principle theoretical investigations of novel transition metal cysteamine systems with halogens are performed by density functional theory. In the first part of this dissertation, we have studied Cu-Cy-X (X = F, Cl, Br, and I). Different spin-multiplicities are considered to understand the electron transition from the occupied to the unoccupied bands. Diffusion barriers of Cu atom to escape out of Cu-Cy-X surface are calculated to mimic the experimentally observed Cu leaching. Our theoretical results show good agreements with the experimental data. As the experimental synthesis of all Cu-Cy-X samples contained Cl as impurity, so it is imperative to understand the effect of Cl in the stability and properties of Cu-Cy-X. Thus, in the second part of this dissertation, we have studied the mixed halogen in Cu-cysteamine Cu-Cy-Cln-X2m (where, X2 = F, Br, and I) and (n = 1, 4, and 7 and m = 8 – n). We have investigated the stability of Cu-Cy-Cln-X2m structures as well as their electronic and optical properties. We have seen the presence of Cl in Cu-Cy-X (X = F, Br, and I) makes the material harder. In the last part of the dissertation, we have considered other possible transition metal cysteamine systems M-Cy-X (M = Co, Ag, Au, and Zn) and (X = F, Cl, Br, and I). Our theoretical results indicate that Ag-Cy and Au-Cy behave like Cu-Cy where all of them stabilize in singlet state. However, Co-Cy and Zn-Cy are stabilized in triplet state which means the mechanism of the optical absorption and emission will be completely different from Cu-Cy. We have also seen in triplet state, Cu-Cy-Cl behaves like semiconductor with a mid-gap state, Ag-Cy as half metal, and Au-Cy-Cl is a metal.

Keywords

Copper cysteamine with halogens, Cu-Cy, Transition metal cysteamine with halogens, M-Cy, Density functional theory (DFT)

Disciplines

Physical Sciences and Mathematics | Physics

Comments

Degree granted by The University of Texas at Arlington

Included in

Physics Commons

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