Preface ....................................................... vii
Acknowledgments ................................................ ix
1 Introduction ................................................. 1
2 Spectroscopic Techniques for Studying Optical Properties
of Nanomaterials ............................................ 11
2.1 UV-visible electronic absorption spectroscopy .......... 11
2.1.1 Operating principle: Beer's law ................. 11
2.1.2 Instrument: UV-visible spectrometer ............. 12
2.1.3 Spectrum and interpretation ..................... 14
2.2 Photoluminescence and electroluminescence
spectroscopy ........................................... 18
2.2.1 Operating principle ............................. 18
2.2.2 Instrumentation: spectrofluorometer ............. 18
2.2.3 Spectrum and interpretation ..................... 20
2.2.4 Electroluminescence (EL) ........................ 23
2.3 Infrared (IR) and Raman vibrational spectroscopy ....... 24
2.3.1 IR spectroscopy ................................. 24
2.3.2 Raman spectroscopy .............................. 26
2.4 Time-resolved optical spectroscopy ..................... 29
2.5 Nonlinear optical spectroscopy: harmonic generation
and up-conversion ...................................... 38
2.6 Single nanoparticle and single molecule spectroscopy ... 40
2.7 Dynamic light scattering (DLS) ......................... 41
2.8 Summary ................................................ 42
3 Other Experimental Techniques: Electron Microscopy and
X-ray ....................................................... 47
3.1 Microscopy: AFM, STM, SEM and ТЕМ ...................... 48
3.1.1 Scanning probe microscopy (SPM): AFM and STM .... 48
3.1.2 Electron microscopy: SEM and ТЕМ ................ 52
3.2 X-ray: XRD, XPS, and XAFS, SAXS ........................ 58
3.3 Electrochemistry and photoelectrochemistry ............. 65
3.4 Nuclear magnetic resonance (NMR) and electron spin
resonance (ESR) ........................................ 67
3.4.1 Nuclear magnetic resonance (NMR) ................ 67
3.4.2 Electron spin resonance (ESR) ................... 69
3.5 Summary ................................................ 72
4 Synthesis and Fabrication of Nanomaterials .................. 77
4.1 Solution chemical methods .............................. 77
4.1.1 General principle for solution-based colloidal
nanoparticle synthesis .......................... 77
4.1.2 Metal nanomaterials ............................. 79
4.1.3 Semiconductor nanomaterials ..................... 84
4.1.4 Metal oxides .................................... 90
4.1.5 Complex nanostructures .......................... 91
4.1.6 Composite and hetero-junction nanomaterials ..... 95
4.2 Gas or vapor-based methods of synthesis: CVD, MOCVD
and MBE ................................................ 96
4.2.1 Metals .......................................... 99
4.2.2 Semiconductors .................................. 99
4.2.3 Metal oxides .................................... 99
4.2.4 Complex and composite structures ............... 101
4.3 Nanolithography techniques ............................ 101
4.4 Bioconjugation ........................................ 102
4.5 Toxicity and green chemistry approaches for
synthesis ............................................. 103
4.6 Summary .......................................... 104
5 Optical Properties of Semiconductor Nanomaterials .......... 117
5.1 Some basic concepts about semiconductors .............. 117
5.1.1 Crystal structure and phonons .................. 118
5.1.2 Electronic energy bands and bandgap ............ 119
5.1.3 Electron and hole effective masses ............. 121
5.1.4 Density-of-states, Fermi energy, and carrier
concentration .................................. 121
5.1.5 Charge carrier mobility and conductivity ....... 123
5.1.6 Exciton, exciton binding energy, and exciton
Bohr radius .................................... 123
5.1.7 Fundamental optical absorption due to
electronic transitions ......................... 125
5.1.8 Trap states and large surface-to-volume
ratio .......................................... 126
5.2 Energy level's and density of states in reduced
dimension systems ..................................... 127
5.2.1 Energy levels .................................. 127
5.2.2 Density of states (DOS) in nanomaterials ....... 130
5.2.3 Size dependence of absorption coefficient,
oscillator strength, and exciton lifetime ...... 132
5.3 Electronic structure and electronic properties ........ 133
5.3.1 Electronic structure of nanomaterials .......... 133
5.3.2 Electron-phonon interaction .................... 135
5.4 Optical properties of semiconductor nanomaterials ..... 135
5.4.1 Absorption: direct and indirect bandgap
transitions .................................... 135
5.4.2 Emission: photoluminescence and Raman
scattering ..................................... 142
5.4.3 Emission: chemiluminescence and
electroluminescence ............................ 147
5.4.4 Optical properties of assembled
nanostructures: interaction between
nanoparticles .................................. 148
5.4.5 Shape dependent optical properties ............. 153
5.5 Doped semiconductors: absorption and luminescence
Optical Properties and Spectroscopy of
Nanomaterials ......................................... 153
5.6 Nonlinear optical properties .......................... 157
5.6.1 Absorption saturation and harmonic
generation ..................................... 157
5.6.2 Luminescence up-conversion ..................... 159
5.7 Optical properties of single particles ................ 160
5.8 Summary ............................................... 165
6 Optical Properties of Metal Oxide Nanomaterials ............ 181
6.1 Optical absorption .................................... 182
6.2 Optical emission ...................................... 187
6.3 Other optical properties: doped and sensitized metal
oxides ................................................ 194
6.4 Nonlinear optical properties: luminescence
up-conversion (LUC) ................................... 197
6.5 Summary ............................................... 199
7 Optical Properties of Metal Nanomaterials .................. 205
7.1 Strong absorption and lack of photoemission ........... 206
7.2 Surface plasmon resonance (SPR) ....................... 207
7.3 Correlation between structure and SPR:
a theoretical perspective ............................. 214
7.3.1 Effects of size and surface on SPR of metal
nanoparticles .................................. 214
7.3.2 The effect of shape on SPR ..................... 217
7.3.3 The effect of substrate on SPR ................. 218
7.3.4 Effect of particle-particle interaction on
SPR ............................................ 218
7.4 Surface enhanced Raman scattering (SERS) .............. 220
7.4.1 Background of SERS ............................. 220
7.4.2 Mechanism of SERS .............................. 221
7.4.3 Distance dependence of SERS .................... 224
7.4.4 Location and orientation dependence of SERS .... 225
7.4.5 Dependence of SERS on substrate ................ 226
7.4.6 Single nanoparticle and single molecule SERS ... 229
7.5 Summary ............................................... 229
8 Optical Properties of Composite Nanostructures ............. 237
8.1 Inorganic semiconductor-insulator and
semiconductor-semiconductor ........................... 239
8.2 Inorganic metal-insulator ............................. 244
8.3 Inorganic semiconductor-metal ......................... 246
8.4 Inorganic-organic (polymer) ........................... 249
8.4.1 Nonconjugated polymers ......................... 249
8.4.2 Conjugated polymers ............................ 250
8.5 Inorganic-biological materials ........................ 253
8.6 Summary ............................................... 257
9 Charge Carrier Dynamics in Nanomaterials ................... 261
9.1 Experimental techniques for dynamics studies in
nanomaterials ......................................... 261
9.2 Electron and photon relaxation dynamics in metal
nanomaterials ......................................... 262
9.2.1 Electronic dephasing and spectral line shape ... 263
9.2.2 Electronic relaxation due to electron-phonon
interaction .................................... 264
9.2.3 Photon relaxation dynamics ..................... 267
9.3 Charge carrier dynamics in semiconductor
nanomaterials ......................................... 271
9.3.1 Spectral line width and electronic dephasing ... 272
9.3.2 Intraband charge carrier energy relaxation ..... 274
9.3.3 Charge carrier trapping ........................ 275
9.3.4 Interband electron-hole recombination or
single excitonic delay ......................... 276
9.3.5 Charge carrier dynamics in doped
semiconductor nanomaterials .................... 282
9.3.6 Nonlinear charge carrier dynamics .............. 283
9.4 Charge carrier dynamics in metal oxide and insulator
nanomaterials ......................................... 288
9.5 Photoinduced charge transfer dynamics ................. 290
9.6 Summary ............................................... 297
10 Applications of Optical Properties of Nanomaterials ........ 305
10.1 Chemical and biomedical detection, imaging and
therapy ............................................... 306
10.1.1 Luminescence-based detection ................... 306
10.1.2 Surface plasmon resonance (SPR) detection ...... 309
10.1.3 SERS for detection ............................. 311
10.1.4 Chemical and biochemical imaging ............... 315
10.1.5 Biomedical therapy ............................. 322
10.2 Energy conversion: PV and PEC ......................... 326
10.2.1 PV solar cells ................................. 326
10.2.2 Photoelectrochemical cells (PEC) ............... 330
10.3 Environmental protection: photocatalytic and
photochemical reactions ............................... 331
10.4 Lasers, LEDs, and solid state lighting ................ 335
10.4.1 Lasing and lasers ............................. 335
10.4.2 Light emitting diodes (LEDs) .................. 336
10.4.3 Solid state lighting: ACPEL ................... 339
10.4.4 Optical detectors ............................. 341
10.5 Optical filters: photonic bandgap materials or
photonic crystals ..................................... 341
10.6 Summary ............................................... 344
Index ......................................................... 359
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