Thesis Format
Integrated Article
Degree
Doctor of Philosophy
Program
Chemistry
Supervisor
Ding, Zhifeng
2nd Supervisor
Zhang, Qiao
Affiliation
Soochow University
Co-Supervisor
Abstract
The unique properties of nanomaterials arise from the nanoscale effects. For instance, the high surface area of nanocatalysts contributes to their enhanced catalytic activity, while the quantum confinement effect in quantum dots leads to the formation of discrete energy levels, granting them remarkable luminescent properties. These characteristics enable broad applications in various fields. In the nanoscale world, the structure of a material determines its functionality, making the study of the structure-property relationship fundamental to the design of nanomaterials.
The first part of this thesis explores the modification of the catalyst’s interfacial structure to enhance photothermal catalysis performance. In chapter 2, widely used commercial Ruthenium catalysts on carbon substrate (Ru/C) were modified using surface ligands to alter their electronic structure. This resulted in a fourfold improvement in polyolefin hydrogenolysis efficiency while achieving the highest reported solid conversion efficiency for polyolefin hydrogenolysis to date. Similarly in chapter 3, TiO₂ photocatalysts were engineered with surface ligands to introduce photochromic properties, achieving a twelvefold increase in polyester glycolysis efficiency due to dynamic catalytic sites and localized thermal effects from expanded light absorption.
The second part of the thesis investigate the relationship between nanomaterial interfacial structures and luminescence. In chapter 4, Nitrogen-doped carbon quantum dots displayed voltage-dependent emission color changes during Electrochemiluminescence (ECL), attributed to functional groups related surface states. Moreover, in chapter 5, graphene quantum dots exhibited competition between surface and aggregation state emissions in ECL. An analysis of their band structures revealed that the sp2-hybridized aromatic structure enhanced their quantum confinement effects. In chapter 6, sulfur quantum dots exhibited ultrabroad emission across 350–1050 nm through reaction enthalpy control. Synergistic analysis revealed the connection between their emission states and synthetic processes. Leveraging this understanding, zinc-doped silicon quantum dots were synthesized in chapter 7, demonstrating high triplet-state selectivity in chemiluminescence, with emission durations exceeding 100 hours and achieved the highest reported absolute chemiluminescence quantum efficiency based on quantum dots. In chapter 8, ECL experiments on ruthenium and palladium complexes showed that molecular symmetry and ligand coordination significantly influence emission wavelengths, laying the groundwork for designing precise nanomaterial structures with specific luminescent properties.
Summary for Lay Audience
Nanomaterials have become a major focus of research across multiple fields this century due to their unique properties. At the nanoscale, the structure of nanomaterials determines their functionality. For instance, nanomaterials of the same composition exhibit vastly different chemical and optical properties when shaped as spheres versus cubes. Consequently, the design and regulation of material structures at the nanoscale is a critical area of study.
It is commonly understood that short-chain organic compounds are highly volatile. However, when these compounds are anchored as ligands on the surface of nanoparticles, they demonstrate exceptional stability and optical properties, even under high temperatures, prolonged light exposure, or extended photoelectric processes. These ligands not only stabilize the structure of the nanomaterials but also enhance their catalytic and optical properties by modulating electronic and band structures.
In this thesis, interfacial structure modification has been used to significantly enhance the performance of well-known commercial catalysts in photothermal plastic degradation, achieving improvements ranging from several-fold to over tenfold. The second part of this thesis investigates the relationship between nanomaterial interfacial structures and their luminescent properties. In quantum dots, phenomena such as surface-state and aggregate-state emissions exhibit different selectivities in ECL, CL, and PL processes, indicating that the same luminophore emits vastly different light depending on the excitation method. These relationships are elucidated through characterization techniques and band structure theory. Additionally, studies on metal-based complexes with precise molecular structures provide insights for the future design of luminescent nanomaterials.
Recommended Citation
Zhang, Congyang, "Investigating Interfacial Structures of Nanomaterials and Their Photochemical and Photoelectrochemical Activities" (2025). Electronic Thesis and Dissertation Repository. 10705.
https://ir.lib.uwo.ca/etd/10705
