SURFACE PROPERTIES AND CHARGE DYNAMICS IN SEMICONDUCTOR MICROCRYSTALS AND NANOCRYSTALS

UoM administered thesis: Unknown

  • Authors:
  • Ruben Ahumada Lazo

Abstract

Semiconductors are the basis of many of the technological devices that have shaped the life as we know it at the present time. Novel compositions in the nanoscale, with improved properties for innovative applications are the core of many research projects that could lead to a sustainable future. In this work, biomimetic In2.77S4 synthetized using Mimosa pudica as a template is evaluated as a photocatalyst for water splitting. By varying the amounts of template, a series of samples are produced and their hydrogen production activities are compared. Structural, morphological, optical, electrochemical and surface characterisations are combined to understand the origin of the enhanced photocatalytic activity of the biomimetic material. Surface composition was found to play a critical role in the dynamics of the photogenerated charge carriers that drive water splitting. In addition, ultrafast laser spectroscopy techniques along with computational modelling allowed the determination of the charge transfer mechanism in quantum dot-electron acceptor conjugates (CdTe/CdS – Q2NS) for efficient redox biosensing. The electron transfer pathway was found to be an ultrafast multistep process with an intermediate hot-trap surface state. The origin of this trap state and the core/shell structure of these quantum dots (QDs) were investigated by X-ray photoelectron spectroscopy (XPS) using synchrotron radiation. Finally, the emission properties and charge dynamics in novel compositions of QDs (CsPbCl3 and Zn3N2) with many potential applications were studied by fluence-dependant ultrafast laser spectroscopy techniques. Parameters such as single exciton and biexciton recombination lifetimes under variable excitation regimes, absorption cross-sections, biexciton interactions, cooling rates and degeneracy of the conduction band minimum were ascertained. Understanding these ultrafast phenomena will help to overcome the limitations that prevent the further implementation of these materials and systems into efficient and commercially viable devices.

Details

Original languageEnglish
Awarding Institution
Supervisors/Advisors
Award date31 Dec 2019