Photoinduced Electron Transfer (ET) Dynamics between Molecular Adsorbates and Semiconductor Nanoparticles with Insulating Metal Oxide Overlayers Open Access

Zhang, Zhe (2008)

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Photoinduced interfacial electron transfer (ET) dynamics between adsorbate materials and mesoporous semiconductor nanoparticles could be investigated with ultrafast infrared and visible spectroscopy. Dependence of ET on insulating metal oxide overlayer and interfacial ET between Quantum Dots and Semiconductor has been studied in this work by choosing appropriate dyes and semiconductor nanoparticles.

The dependence of ET dynamics on the number of Al2O3 and TiO2 insulating overlayers has been studied with ultrafast transient spectroscopy. The system of RhB-Al2O3-SnO2 was chosen because ET dynamics for the RhB-SnO2 system was expected to be relatively fast enough to be completed within 1ns detection time window, thereby facilitating our comparison among injection dynamics. Injection yield was shown to decrease with the increase of the number of Al2O3 overlayers. Electron injection dynamics was shown to be slowed down as the number of Al2O3 overlayers increases in both transient infrared and visible experiment. For the RuN3-TiO2-SnO2 and C343-TiO2-SnO2 systems, the injection yields decrease with the increase of number of TiO2 overlayers from zero to two. However, the injection yields for that with 3 three overlayers is always larger. Detail is still to be understood.

ET dynamics from TOPO capped CdSe QDs to TiO2 nanoparticles were also monitored with ultrafast transient spectroscopy. No electron transfer was observed from the analysis of both transient mid-IR and transient visible experiments. Thiol and dithiocarbamate capped CdSe QDs were successfully prepared in an effort for the following preparing TiO2-CdSe nanocomposite. However, unfortunately, the ligand exchanged QDs were not favorable because of the photostability problem and insufficient absorption onto TiO2.

Table of Contents

Chapter 1 Introduction

1.1 General Introduction

1.2 ET Dynamics on Adsorbates/Nanoparticles Composite

1.2.1 Dependence of ET on insulating Metal Oxide Overlayer

1.2.2 ET between Quantum Dots and Semiconductor

1.3 Summary


Chapter 2 Experimental Section

2.1 Preparation of Semiconductor Colloid, Nanoporous Films and Nanocomposites

2.1.1 Preparation of TiO2 Colloid and Films

2.1.2 Preparation of SnO2 Colloid and Films

2.1.3 Preparation of ZrO2 Films

2.1.4 Preparation of RhB-Al2O3- SnO2Nanocomposite

2.1.5 Preparation of RuN3-TiO2- SnO2and C343-TiO2- SnO2 Nanocomposites

2.1.6 Preparation of TiO2-CdSe and ZrO2-CdSe nanocomposite

2.2. Sensitizers Used in This Work

2.2.1 Rhodamine B and Coumarin 343

2.2.2 RuN3 dye

2.3 Photostability study with a UV-vis spectrophotometer

2.4 Ultrafast Transient Absorption Measurement

2.4.1 Ultrafast Infrared Transient Absorption Measurement

2.4.2 Ultrafast Visible Transient Absorption Measurement

2.5 Fluorescence lifetime measurements


Chapter 3 Dependence of Electron transfer on Insulating Al2O3 Overlayer in RhB-SnO2 films

3.1 Ultrafast Infrared Transient Absorption measurement for RhB- Al2O3-SnO2

3.2 Ultrafast visible Transient Absorption measurement for RhB-Al2O3-SnO2

3.3 Summary


Chapter 4 Dependence of Electron transfer on Insulating TiO2 Overlayer in RuN3-SnO2 and C343-SnO2 films

4.1 Ultrafast transient infrared spectroscopy of SnO2- TiO2 -RuN3

4.2 Ultrafast transient infrared spectroscopy of SnO2-TiO2 -C343

4.3 Summary


Chapter 5 Interfacial Dynamic Study on the Film-based TiO2-CdSe Nanocomposite

5.1 Photochemical stability of TiO2-TOPO-CdSe nanocomposite

5.2 Transient absorption dynamics for TiO2-TOPO-CdSe Nanocomposite

5.3 Fluorescence lifetime measurements for TiO2-TOPO-CdSe

5.4 Preparation of TiO2-CdSe nanocomposite with shorter bridge Molecules

5.5 Summary


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