In this work, photocatalytic bismuth vanadate microparticles of different morphologies were investigated as artificial single.component microswimmers. In the first chapter, the motion mechanism as well as influence factors on the motion behavior such as solution pH and solution conductivity, hydrogen peroxide fuel concentration and decomposition kinetics and the surface charge of the particles were studied in detail. Furthermore, fluid flow profiles around the particles were determined.
In the following chapter, interactions between the microswimmers were studied and exploited to create active assemblies that can be used to integrate multiple functionalities in one assembly.
Eventually, alternative propulsion mechanisms besides hydrogen peroxide fuel decomposition were studied. The presented approaches include the catalysis of an organic oxidation and photoreduction of noble metals onto the particles, which proved to increase their catalytic activity and enabled propulsion of the modified microswimmers in pure water.:Acknowledgments III
List of Abbreviations V
1. Introduction 1
2. Fundamentals of Photocatalysis and Active Matter 5
2.1. Photocatalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1. Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2. Processes in Semiconductor Photocatalysis . . . . . . . . . . . . . . . . 5
2.1.3. Properties of Bismuth Vanadate . . . . . . . . . . . . . . . . . . . . . . 10
2.1.4. Photocatalytic H2O2 decomposition . . . . . . . . . . . . . . . . . . . . 12
2.2. Active Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.1. Motion at the Microscale . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.2. Mechanisms of Catalytic Active Motion . . . . . . . . . . . . . . . . . . 18
2.2.3. Light-Driven Active Motion . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.4. Origin of Asymmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3. Aim and Motivation 27
4. Results and Discussion 29
4.1. Microparticle Synthesis und Characterization . . . . . . . . . . . . . . . . . . . 29
4.1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.1.2. Syntheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.1.3. Characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4.1.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
4.2. Motion Studies and Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2.2. Characterization of Active Motion . . . . . . . . . . . . . . . . . . . . . 44
4.2.3. Influence of Experimental Conditions . . . . . . . . . . . . . . . . . . . . 54
4.2.4. Adjustment of Motion Mode by pH . . . . . . . . . . . . . . . . . . . . . 67
4.2.5. Flow Fields Around Single Crystalline Microparticles . . . . . . . . . . . 73
4.2.6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
4.3. Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
4.3.2. Interactions Between BiVO4 Microswimmers . . . . . . . . . . . . . . . 83
4.3.3. Interactions between Spheroidal Microswimmers . . . . . . . . . . . . . 84
4.3.4. Surface Modification of Spheroidal Microswimmers . . . . . . . . . . . . 88
4.3.5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4.4. Towards Alternative Propulsion Reactions . . . . . . . . . . . . . . . . . . . . . 93
4.4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
4.4.2. Oxidation of Dibenzylamine . . . . . . . . . . . . . . . . . . . . . . . . . 94
4.4.3. Photodeposition of Metals . . . . . . . . . . . . . . . . . . . . . . . . . . 97
4.4.4. Towards Propulsion in Pure Water . . . . . . . . . . . . . . . . . . . . . 98
4.4.5. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
5. Summary and Final Remarks 103
6. Experimental Details 113
6.1. Syntheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
6.1.1. Microparticle Synthesis and Characterization . . . . . . . . . . . . . . . 113
6.1.2. Motion Studies and Mechanism . . . . . . . . . . . . . . . . . . . . . . . 114
6.1.3. Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
6.1.4. Towards Alternative Propulsion Reactions . . . . . . . . . . . . . . . . . 117
6.2. Apparatus and Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
6.2.1. Scanning Electron Microscopy (SEM) . . . . . . . . . . . . . . . . . . . 117
6.2.2. Transmission Electron microscopy (TEM) . . . . . . . . . . . . . . . . . 117
6.2.3. Nitrogen physisorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.2.4. Gas Chromatography (GC) . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.2.5. Powder X-ray Crystallography (XRD) . . . . . . . . . . . . . . . . . . . 118
6.2.6. Absorption Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.2.7. Fluorescence Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.2.8. Zeta Potential Measurements . . . . . . . . . . . . . . . . . . . . . . . . 119
6.2.9. Fluorescence Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6.2.10. Light Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
A. Appendix 123
Bibliography 139
List of Publications 149
Erklärung 151
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:76961 |
| Date | 13 December 2021 |
| Creators | Heckel, Sandra |
| Contributors | Simmchen, Juliane, Eychmüller, Alexander, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 10.1021/acs.langmuir.0c01568, 10.3390/catal11050599, 10.1002/aisy.201900093, 10.1002/cnma.202100119 |
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