TiO2 Nanotube Arrays (eBook)

Preface 5
Contents 7
Introduction 12
References 23
Chapter 1: Fabrication of TiO2 Nanotube Arrays by Electrochemical Anodization: Four Synthesis Generations 27
Introduction 27
The Electrochemical Anodization Process 28
Nanotube Array Synthesis Using Aqueous Electrolytes: The First Generation 29
HF-Based Electrolytes 29
Tapered Conical Shape Nanotubes 31
Wall Thickness Variation 32
Using HNO3/HF 33
Using H2SO4/HF 34
Using H2Cr2O7/HF 34
Using CH3COOH/NH4F, H2SO4/NH4F 35
Using H3PO4/HF, H3PO4/NH4F 36
Effect of Different Cathode Metals 36
Nanotube Array Synthesis Using Buffered Electrolytes: The Second Generation 38
Step-by-Step Procedure: Solution Preparation, Mixing and pH Adjustment 41
Solution Set Preparation 41
Anodization with Constant Current Density 42
Synthesis of Nanotube Arrays Using Polar Organic Electrolytes: The Third Generation 44
Using Formamide and Dimethyl formamide electrolyte 44
Dimethyl Sulfoxide Electrolytes 48
Ethylene Glycol Electrolytes 52
Membrane Fabrication 56
Diethylene Glycol Electrolytes 60
Using Glycerol and NH4F 63
Methanol, Water, and HF 64
Nanotube Array Synthesis Using Non-Fluoride Based Electrolytes: The Fourth Generation 64
Using HCl 66
H2O2 Aqueous Electrolytes 66
HCl/H2O2 Aqueous Electrolytes 68
Fabrication of Transparent TiO2 Nanotubes Arrays 70
Mechanistic Model of Nanotube Array Formation by Potentiostatic Anodization 74
References 85
Chapter 2: Material Properties of TiO2 Nanotube Arrays: Structural, Elemental, Mechanical, Optical, and Electrical 93
Introduction 93
Structural and Elemental Characterization 93
Anodic Formation of Crystalline Metal Oxide Nanotubes 99
Improved Crystallization via Solvothermal Treatment 102
Partially Crystalline Anatase Phase Nanotubes by Anodization 104
Characterization of Doped Titania Nanotubes 105
Carbon Incorporation Within the Nanotubes 105
Nitrogen Incorporation Within the Nanotubes 106
Boron-Doped Nanotubes 108
Organic Bath 108
CdS-Coated Nanotubes 109
Optical Properties of Titania Nanotubes Arrays 109
Finite Difference Time Domain Simulation of Light Propagation in Nanotube Arrays 109
Measured Optical Properties 114
Ellipsometric Measurements 118
Raman Spectra Measurements 122
Electrical Property Measurements 123
Photocurrent Transient Measurements 123
Capacitance Measurements 124
Mott-Schottky Plots: Analysis of Interfacial Properties 125
Surface State Model 128
Photoeffects 130
Mechanical Properties 131
References 132
Chapter 3: TiO2 Nanotube Arrays: Application to Hydrogen Sensing 140
Introduction 140
High Temperature Sensors using TiO2 Nanotube Arrays 142
Self-Cleaning Room-Temperature Hydrogen Sensors 146
Room-Temperature Hydrogen Sensors of Enhanced Sensitivity 151
TiO2 Nanotube Arrays on Ti Foil 151
Transparent Hydrogen Sensors 156
Extreme Hydrogen Gas Sensitivities at Room Temperature 157
Transcutaneous Hydrogen Monitoring using TiO2 Nanotube Arrays 161
Cross Interference and Calibration 162
Transcutaneous Hydrogen and Lactose Intolerance 166
References 167
Chapter 4: TiO2 Nanotube Arrays: Application to Photoelectrochemical Water Splitting 173
Introduction 173
Photoelectrolysis Cell 174
Water Splitting Efficiency 177
Two Electrode Configuration 177
Three-Electrode Configuration 178
Efficiency Comparison Determined Using Two- and Three-Electrode Configurations 180
Quantum Efficiency Calculation 181
Photoelectrolysis Using Unmodified TiO2 Nanotubes 182
Short Nanotubes 183
Medium Length Nanotubes 185
Long Nanotubes 188
Roughness Factor 190
Effect of Electrolyte Additives 192
Photoelectrolysis Using Anionic and Cationic Doped TiO2 Nanotubes 194
N-Doped TiO2 Nanotubes 194
Carbon Doped TiO2 Nanotubes 198
Sulfur-Doped TiO2 Nanotubes 199
Boron-Doped TiO2 Nanotubes 200
Silicon-Doped TiO2 Nanotubes 201
Photoelectrolysis Using Surface-Sensitized TiO2 Nanotubes 202
CdS Sensitized TiO2 Nanotubes 202
CdSe Sensitized TiO2 Nanotubes 204
CdTe Sensitized TiO2 Nanotube Arrays [137] 204
WO3 Coated TiO2 Nanotubes 207
Pt Sensitized TiO2 Nanotubes 208
Other Approaches 209
Polyoxophosphotungstate Encapsulated in TiO2 Nanotubes 209
Light Sensitized Enzymatic System with TiO2 Nanotubes 210
Self-Biased Photoelectrochemical Diodes Using Cu-Ti-O Ternary Oxide Nanotubes 212
Fabrication of p-Type Copper Rich Cu-Ti-O Nanotubes 213
Photoelectrochemical Properties 216
Self-Biased Heterojunction Photoelectrochemical Diodes 217
Benefits of nanostructuring hematite 219
Self-Aligned Nanoporous Iron (III) Oxide 219
Photoelectrochemical Properties of Self-Aligned Nanoporous Iron (III) Oxide 222
Fabrication and Structural Characterization of Ti-Fe-O Nanotubes 222
Photoelectrochemical Properties of Ti-Fe-O Nanotubes 227
Compositionally Graded Ternary Oxide Nanotube Arrays 229
References 230
Chapter 5: Dye-Sensitized and Bulk-Heterojunctions Solar Cells: TiO2 Nanotube Arrays as a Base Material 241
Introduction 241
Dye Sensitized Solar Cells: Operating Principles 242
Key DSC Processes 243
Factors Influencing Conversion Efficiencies 244
Nanocrystalline DSCs 247
Solar Cell Parameters 249
J-V Characterization Under Standard Conditions 250
Calibrating the Solar Simulator for DSC and Polymeric Solar Cells 250
Experimental Setup 251
Benefits of Vertically Oriented Uniformly Aligned TiO2 Nanotube Arrays in DSCs 252
Finite Difference Time Domain Application to DSCs 253
FDTD Simulations 254
Validation of Computational Model 257
Liquid Junction DSCs 263
Transparent TiO2 Nanotube Arrays on FTO Coated Glass: Front Side Illumination 263
TiO2 Nanotube Arrays on Ti Foil: Back Side Illumination 269
Charge Collection Properties 276
Electron Transport and Recombination Properties 277
Polymer Based Bulk Heterojunction Solar Cells 282
TiO2 Nanotubes on FTO Glass: Polymeric Bulk Heterojunction Solar Cells 286
Solar Cell Fabrication and Performance 290
TiO2-Polymer Based Solar Cells: Back Side Illumination Geometry 294
References 298
Chapter 6: Use of TiO2 Nanotube Arrays for Biological Applications 308
Introduction 308
Biosensors 309
H2O2 Detection: Nanotubes Co-immobilizedwith HRP and Thionine 309
Co-Immobilized with Cytochrome c 311
Detection of H2O2 and Glucose 311
Enhanced Blood Clotting 313
Cell Adhesion and Osteoblast Growth 315
Drug Elution from TiO2 Nanotubes 319
Hydrophobic Nanotubes: SAMs on Surface on Hydrophilic Nanotubes 324
Biological Fluids Filtration and Drug Delivery Using TiO2 Nanotubular Membrane 325
Application of Photocatalytic TiO2 Nanotube Properties 331
References 332
Chapter 7: Conclusions and New Directions 338
Conclusions 338
Some Future Directions 343
Intercalation and Supercapacitors 343
CO2 Reduction Using Visible Light 352
References 363
Index 369