Date of Award

8-22-2025

Date Published

September 2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Weiwei Zheng

Keywords

CdS;Co-catalysts;Dopants;Nanocrystals;Pervoskites;Photocatalysis

Subject Categories

Chemistry | Physical Sciences and Mathematics

Abstract

Semiconductor nanocrystals (NCs) are sought after for their applications in photocatalysis and photovoltaics and due to their impressive optical and electronic properties. In photocatalysis, an important green energy transformation is sunlight utilization to produce hydrogen gas via photocatalytic water splitting. However, the photocatalytic performance of pristine semiconductors is low due to their inherent fast charge recombination. The use of co-catalysts with semiconductor NCs leads to enhanced photocatalytic product generation; noble metal co-catalysts, such as Pt, Au, Ag, and Cu and noble-metal-free metal hydroxide co-catalysts on either chalcogenide CdS or perovskite CsPbX3 (X = Cl, Br) semiconductors were synthesized to study the changes in photophysical properties. Yet, co-catalysts alone are not enough to improve the photocatalytic properties of the semiconductor hybrids. Therefore, Mn2+ dopants are introduced, which have a significantly longer lifetime (∼ms) than that of host excitons (∼ns), facilitating charge separation for resulting enhancement of the photocatalytic performance. The long-lived lifetime from the Mn2+ dopants is on a similar timescale of surface photocatalytic reactions, which resulted in significant enhancement of photocatalysis. The Mn2+ dopants act as a bridge between the light harvesting semiconductors and the active site co-catalyst during photocatalysis. Furthermore, we studied the changes in the Mn2+ doped semiconductors’ photovoltaic properties upon addition of localized surface plasmon resonance (LSPR) active co-catalysts. When LSPR interacts with Mn2+ dopants, the photophysical properties of the semiconductor hybrid can be altered to enhance specific properties such as emission yield. Controlling the interactions between co-catalysts and Mn2+ dopants in semiconductors is fundamentally important for altering the photocatalytic and photovoltaic properties of semiconductors.

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