Introduction to Nanotechnology

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Excitatior I [eV]: 2.175 2.214 2.255 2.296 2.318 2.340 2.385 2.431 -& 2.455 2.480 2.531 8.3. LUMINESCENCE 21 7 Excitation [ev]: 2.175 2.431 & 2.455 ~ I I I I I I I I I I I I I I 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 1.8 2 2.2 2.4 2.6 Photon Energy (eV) Photon Energy (eV) (a) (b) Figure 8.27. Fluorescence spectra for 3.2-nm-diameter CdSe nanocrystals for various indicated excitation energies at 77 K: (a) experimental and (b) simulated spectra. For comparison purposes, the experimental absorption spectrum is shown at the bottom left. [From W. Hoheisel, V. L. Colvin, C. S. Johnson, and A. P. Alivisatos, J. Cbem. Pbys. 101, 8455 (1994).] Figure 8.28. Fluorescence spectra for two samples of CdS nanoparticles obtained before (solid lines) and after (dashed lines) the addition of 10-3M nitromethane CH3N02. [From A. Hasselbarth, E. Eychmuller, and H. Well, Cbem. Pbys. Lett. 203, 271 (1993).]
218 OPTICAL AND VIBRATIONAL SPECTROSCOPY emission at longer wavelengths. We also see from this figure that the addition of nitromethane (CH3N02) quenches the fluorescence by bringing about a shift toward longer wavelengths, plus an appreciable decrease in the magnitude of the broad band, and in addition it practically eliminates the sharp exciton emission. The temperature dependence of the excitonic and trapped carrier recombination fluorescence bands from CdS nanoparticles both exhibit a decrease in intensity and a shift toward longer wavelengths when the temperature is raised from 4 to 259K, as illustrated in Fig. 8.29. These spectral data suggest that the hole traps lie much deeper (i.e., have much lower energies) than do electron traps. To try and elucidate the mechanisms involved in the exciton relaxation and the detrapping of electrons, the time dependencies of the excitonic fluorescence and the trapped fluorescence were determined at a series of temperatures from 4 to 269 K, and the results are displayed in Figs. 8.30 and 8.3 1, respectively. Both types of decay were found to have a complicated multiexponential behavior, with the rates of decay changing as the processes proceeded. The decay time was shortest for the excitonic emission at intermediate temperatures, requiring the time z1/2 of less than 10 ns for the decay to reach half of its initial intensity at 121 K. In contrast to this, the trapped fluorescence decayed much more slowly, being particularly slow at intermediate temperatures, with the rate constant rl,2 - l00nsec at 70K. It had been determined independently that the trapping of electrons in CdS nanoparticles is extremely fast, in the picosecond (ps) time range requiring 10-13s or less time to complete the trapping, so all the trapped electrons are in place before there is an appreciable onset of the fluorescence. To probe into spectral changes that take place during the initial extremely short picosecond timescale (1OOOps = 1 ns, or 1 ps = lO-'ns = s), the data from decay curves of the type presented in Figs. 8.30 and 8.3 1 were used to reconstruct Wavelength (nrn) Figure 8.29. Fluorescence spectra of CdS nanoparticles (sample II of Fig 8.28) recorded at a series of temperatures from 4 to 259 K, using A = 360 nm excitation. [From A. Eychmuller, A. Hasselbarth, L. Katsicas, and H. Weller, Ber. Bunsen-Ges. Phys. Chem. 95, 79 (1991).]
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INTRODUCTION TO NANOTECHNOLOGY Char
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CONTENTS Preface xi 1 Introduction
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5.2 Carbon Molecules 103 5.2.1 Natu
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9.4 Excitons 244 9.5 Single-Electro
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PREFACE In recent years nanotechnol
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INTRODUCTION The prefix nano in the
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INTRODUCTION 3 he recognized the ex
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1000 (I) a 900 4 800 a 900 I 6 700
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INTRODUCTION 7 developed before the
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2.1. STRUCTURE 9 mechanics, the res
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X T 2.1. STRUCTURE 11 Figure 2.4. C
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2.1. STRUCTURE 13 Figure 2.6. Thirt
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Sodium Nanoparticle Na, Magic Numbe
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2.1. STRUCTURE 17 of the large anio
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2.1. STRUCTURE 19 other, and high-f
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2.2. ENERGY BANDS 21 Conduction Ban
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2.2. ENERGY BANDS 23 Figure 2.13. S
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2.2. ENERGYBANDS 25 band at point T
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A X ' Wavevector A Si c z 2.2. ENER
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2.2. ENERGY BANDS 29 bands of Figs.
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2.3. LOCALIZED PARTICLES 31 add ele
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1 meV 10 meV 100 meV FJ E W 1 eV 10
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3 METHODS OF MEASURING PROPERTIES 3
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3.2. STRUCTURE 37 Table 3.1. Crysta
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3.2. STRUCTURE 39 Figure 3.2. Two-d
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3.2. STRUCTURE 41 The widths of the
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44 METHODS OF MEASURING PROPERTIES
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3.3. MICROSCOPY 51 types of transit
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3.3. MICROSCOPY 53 Actual diverging
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Tunneling current Tunneling current
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3.3. MrCAOSCOPY 57 and the latter m
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3.4. SPECTROSCOPY 59 From Eq. (3.8)
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1 Average Panicle FWHM Size (nm) in
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CdSe colloidal NCs a = 1.2 nrn 3.4.
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El X-RAY TUBE 8000 - A 6000 - 4000
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2 N I w 3.0 2.5 2.0 1.5 1 .o 0.5 3.
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i 3.4. SPECTROSCOPY 69 NMR involves
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T=220K - 2G H FURTHER READING 71 Fi
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NUMBER OF ATOMS RADIUS (nm) 1 10 1
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I L 7 3 5 7 9 11 13 15 17 NUMBER OF
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JELLIUM MODEL OF CLUSTERS ATOMS CLU
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1.02 { 1.01 - 1 - 0.99 - 4.2. METAL
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4.2. METAL NANOCLUSTERS 81 Figure 4
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4.2. METAL NANOCLUSTERS 83 Figure 4
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-0 100 200 300 400 500 600 MASSICHA
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a 42. METAL NANOCLUSTERS 87 Figure
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. . . .. . - . D 111111111111111111
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3 4 2.5 0 cn g 2 0 z d 1.5 t a 9 1
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4.3. SEMICONDUCTING NANOPARTICLES 9
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4.4. RARE GAS AND MOLECULAR CLUSTER
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4.5. METHODS OF SYNTHESIS 97 d Figu
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4.5. METHODS OF SYNTHESIS 99 isopro
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PULSED LASER BEAM 1 1 1 1 1 I ROTAT
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5.1. INTRODUCTION CARBON NANOSTRUCT
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5.2. CARBON MOLECULES 105 methane d
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5.3. CARBON CLUSTERS 107 -0 20 40 6
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PHOTON ENERGY (electron volts) 5.3.
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Figure 5.6. Structure of the CEO fu
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1 30 0 14.1 14.2 14.3 14.4 14.5 LAT
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(c) 5.4. CARBON NANOTUBES 115 Figur
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5.4. CARBON NANOTUBES 1 17 The mech
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5.4. CARBON NANOTUBES 11 9 investig
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5.4. CARBON NANOTUBES 121 energy gr
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5.4. CARBON NANOTUBES 123 stretch c
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5.5. APPLICATIONS OF CARBON NANOTUB
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- v) 450 : 400 3 350 1 300 : 5 250
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BULK NANOSTRUCTURED MATERIALS In th
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h 8 0 6.1. SOLID DISORDERED NANOSTR
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6.1. SOLID DISORDERED NANOSTRUCTURE
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6.2. NANOSTRUCTURED CRYSTALS 153 qu
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6.2. NANOSTRUCTURED CRYSTALS 155 Fi
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158 BULK NANOSTRUCTURED MATERIALS 6
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160 BULK NANOSTRUCTURED MATERIALS w
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162 BULK NANOSTRUCTURED MATERIALS 0
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164 BULK NANOSTRUCTURED MATERIALS n
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Page 198 and 199: 7.7. FERROFLUIDS 187 Figure 7.22. M
Page 200 and 201: 7.7. FECIROFLUIDS 189 Figure 7.25.
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Page 204 and 205: FURTHER READING FURTHER READING 193
Page 206 and 207: 10- IR f IA -1 8.1. INTRODUCTION 19
Page 208 and 209: 8.2. INFRARED FREQUENCY RANGE 197 1
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Page 214 and 215: 8.2.3. Raman Spectroscopy 8.2. INFR
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Page 218 and 219: - r I 520 51 8 v 6 516 a" 51 4 51 2
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Page 226 and 227: - ? m v .- - z In C a, c C - .. . .
Page 230 and 231: 6 100 200 300 Time (ns) 8.3. LUMINE
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Page 236 and 237: FURTHER READING 225 P. Milani and C
Page 238 and 239: 9.2. PREPARATION OF QUANTUM NANOSTR
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Page 242 and 243: 9.3. SIZE AND DIMENSIONALITY EFFECT
Page 248 and 249: w n 3 2 1 9.3. SIZE AND DIMENSIONAL
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Page 256 and 257: 9.5. SINGLE-ELECTRON TUNNELING 245
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Page 264 and 265: 9.7. SUPERCONDUCTIVITY 253 horizont
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Page 270 and 271: 10.1. SELF-ASSEMBLY 259 factor of 2
Page 272 and 273: (a) (LI (dl 10.1. SELF-ASSEMBLY 261
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10.2. CATALYSIS 267 where the lengt
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10.2. CATALYSIS 269 are also other
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1600 2 1200 t p - Bi2M020, 10.2. CA
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7 - I 2,330 m .- c r 0 2 2,300 - u)
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10.2. CATALYSIS 275 with a top and
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10.2. CATALYSIS 277 based on the pr
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10.2. CATALYSIS 279 CnHlnfl, which
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I1 ORGANIC COMPOUNDS AND POLYMERS 1
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11.2. FORMING AND CHARACTERIZING PO
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1 1.3. NANOCRYSTALS 285 This expres
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-1 5 0) C a, -1 1 000 300 100 30 10
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11.3. NANOCRYSTALS 289 Table 11.1.
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11.3. NANOCRYSTALS 291 R’ groups
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11.4. POLYMERS 293 Figure 11.9. Ske
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11.5. SUPRAMOLECULAR STRUCTURES 295
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M Et3P OTf M=Pd M=Pt M=Pd, 41 % M=P
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11.5. SVPRAMOLECUUAR STRUCTURES 2s
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11 5. SUPRAMOLECULAR STRUCTURES 303
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BiodegradaWe surface 4 Functional g
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FURTHER READING 309 F. J. Owens and
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12.2. BIOLOGICAL BUILDING BLOCKS 31
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314 BIOLOGICAL MATERIALS which we w
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316 BIOLOGICAL MATERIALS Table 12.2
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318 BIOLOGICAL MATERtALS i J / Flgu
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320 BIOLOGICAL MATERIALS Pyrimidine
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322 BlOLMjlCAL MATERiALS (a) DNA do
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324 BIOLOGICAL MATERIALS so each wo
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326 BIOLOGICAL MATERIALS 12.4.2. Mi
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328 BIOLOGICAL MATERIALS tions they
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330 BIOLOGICAL MATERIALS hardened f
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13 NANOMACHINES AND NANODEVICES In
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334 NANOMACHINES AND NANODEVICES CA
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336 NANOMACHINES AND NANODEVICES Op
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338 NANOMACHINES AND NANODEVICES ti
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340 NANOMACHINES AN0 NANODEVICES PO
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342 NANOMACHINES AND NANODEVICES X
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344 NANOMACHINES AND NANODEVICES na
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346 NANOMACHINES AND NANODEVICES 31
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348 NANOMACHINES AND NANODEVICES -
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350 NANOMACHINES AND NANODEVICES re
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352 NANOMACHINES AND NANODEVICES 1
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354 NANOMACHINES AND NANODEVICES -1
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A.l. INTRODUCTION APPENDIX A FORMUL
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A.3. PARTIAL CONFINEMENT 359 limiti
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APPENDIX B TABULATIONS OF SEMICONDU
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TABULATIONS OF SEMICONDUCTING MATER
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Table B.8. Effective masses m+ rela
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372 INDEX amoeba, 3 16 amphiphilic,
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374 INDEX CdS, 9, 130, 213, 216, 36
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376 INDEX dispersion, 277 disulfide
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378 INDEX Ga (gallium) (continued)
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380 INDEX length (continued) critic
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382 INDEX multiple ionization, 93 r
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384 INDEX pi-conjugation, 282, 292
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silica, 269 silica-alumina, 269, 27
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388 INDEX wavefimction (continued)
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Introduction to Nanotechnology

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