Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.

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IðqÞ ¼ Ið0Þexpð q 2 R 2 g =3Þ; where Ið0Þ is the scattering intensity at zero angle[30]. For spherical p ffiffiffiffiffiffiffi paticles, the particle radius R g relates to the particleradius as R ¼ R g 5=3 . Rg is the volume-weighted average in a polydispersedispersion. As a general guide, the Guinier approximation applies whenRq V 1, although this may vary depending on particle geometry and polydispersity.For values of Rq > 1, I( q) oscillates from spherical scatterers due toconstructive and destructive interference of x-rays scattered from individualparticles. A representation of the scattering data as a Porod plot [I( q)q 4 versusq] visually enhances the oscillations for more accurate curve fitting of theexperimental and modeled intensities. Fitted curves are usually generatedfrom analytic expressions based on the shape and polydispersity of a collectionof independent scatterers, although atomistic models have also beenreported in the literature [31]. For example, P( q) for a monodisperse sphere ofconstant core density is [13,30]" # 2sinðqRÞ qRcosðqRÞPðqÞ ¼ 3ðqRÞ 3The sample polydispersity strongly affects P( q) and must be accounted for tofit scattering curves of real samples. The scattering intensity can be calculatedwhen the shape of the size distribution is known usingIðqÞ ¼Z l0NðRÞPðqÞR 6 dRð1Þwhere N(R) is the normalized number distribution as a function of particleradius, typically taken as a Gaussian or log-normal distribution. The shape ofthe size distribution must be assumed to determine the nanocrystal size andsize distribution from the scattering data; however, this can be checked bycomparison with histograms generated from TEM images of nanocrystals. Afit of Eq. (1) to the experimental data provides the average radius andstandard deviation of the particles. The polydispersity damps the scatteringoscillations in the Porod region and standard deviations in particle sizeabove f20% nearly eliminate the oscillations, decreasing the usefulness ofSAXS for sizing nanocrystal samples with broad size distributions.For nanocrystal dispersions in which interparticle interactions are importantor for concentrated solutions where the molecular motion isinhibited, S( q) p 1 and I( q) deviates from P( q) at low q values [10,30].Positive deviations from the shape factor indicate interparticle attraction andmay be characterized by the presence of dimers or the flocculated particles (ora negative second virial coefficient) [10]. Conversely, a negative departure ofthe scattering curve from the shape factor indicates strong interparticlerepulsion.Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.
Figure 8 The gold nanocrystal film shown on the left was prepared by drop-casting aconcentrated dispersion onto a polymer window. A penny is shown on the right toillustrate the typical size of the film studied by SAXS.C. Nanocrystal Thin FilmsSmall-angle x-ray scattering is an ideal tool to characterize condensed nanocrystalfilms, as it probes a relatively large region of sample and provides anaveraged value of the structural order and symmetry of the superlattice, orglassy structure. Because P( q) can be measured directly from dispersions,Figure 9 (a) Small-angle scattering data from a dispersion of gold nanocrystals(R = 2.75 nm F 10%) in hexane (curve A) and diffraction pattern from a thin film ofthe dispersion drop-cast onto a polymer substrate (curve B). The structure factor[S( q)] (curve C) is determined from the diffraction pattern. (b) The correspondingradial distribution function [ g(r)] for the thin film is calculated from a Fouriertransformation of S( q).Copyright 2004 by Marcel Dekker, Inc. All Rights Reserved.
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Copyright 2004 by Marcel Dekker, In
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This book covers several topics of
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esult, some exciting topics were no
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3. Fine Structure and Polarization
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9. III-V Quantum Dots and Quantum D
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ContributorsUri BaninThe Hebrew Uni
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1‘‘Soft’’ Chemical Synthesi
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structure of energy states leads to
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growth can proceed by Ostwald ripen
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Figure 3 Transmission electron micr
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Figure 4 Temporal evolution of the
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No. 26, are f85% (Fig. 6) [21]. Alt
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tion spectra and broad PL spectra.
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ing surface-to-volume ratio with di
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Figure 8 Photoluminescence spectra
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lattice mismatch. Such a large latt
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match between InAs and ZnS of f11%.
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successfully repeated for up to thr
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Under a different growth regime, on
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Figure 14 Atomic model of the CdSe
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‘‘Teardrop-shaped’’ particl
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Figure 17 High-resolution TEMs of C
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allows isolation of tetrapods in f8
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ligand concentrations yield a reduc
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een determined and quantitatively c
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tion volumes were also shown to be
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synthesis temperatures of z400jC ar
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Figure 23 (a) Photoluminescence spe
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levels (fV1 Mn per NQD). Despite in
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Figure 25 X-ray diffraction pattern
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Figure 27 Transmission electron mic
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An additional factor that strongly
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Figure 30 (a,b) Schematics illustra
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Slow, controlled precipitation of h
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Figure 34 Schematic illustrating th
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Figure 36 Transmission electron mic
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achieving biological compatibility
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47. Yu H.; Gibbons P.C.; Kelton K.F
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2Electronic Structure inSemiconduct
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Figure 2 (a) Simple model of a nano
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electron and hole to be treated as
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independently, Eq. (13) is commonly
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a better description of the bulk ba
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investigated. For optical experimen
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Figure 4 (a) Absorption (solid line
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Figure 6 Normalized PLE scans for s
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Figure 8 A simplistic model for des
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Figure 10 Theoretically predicted p
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Figure 12 Schematics depicting the
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Figure 14 Calculated band-edge exci
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Figure 15 Absorption (solid line) a
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Figure 18 (a) Calculated band-edge
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IV.BEYOND CdSeA. Indium Arsenide Na
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the six-band Luttinger Hamiltonian.
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11. Norris, D.J.; Efros, Al.L.; Ros
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69. Gaponenko, S.V.; Woggon, U.; Sa
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formation of a long-lived dark exci
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where the constant A is determined
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In crystals for which the function
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The respective wave functions areC
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passive, as was shown in Ref. 12. T
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square of the matrix element of the
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where e F = e F ieV and e F F = e x
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see that for all nanocrystal shapes
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optical recombination of the excito
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B. Recombination of the Dark Excito
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where x = cos h and f = l B g e H/3
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The theory of the polarization memo
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Figure 7 The size dependence of the
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state would have an infinite lifeti
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crystal axis [see Eq. (40)]. As a r
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time of the exciton momentum relaxa
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One must also account for the influ
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observed in one of the first studie
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REFERENCES1. Bawendi, M.G.; Wilson,
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4Intraband Spectroscopyand Dynamics
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The solid line in Fig. 1 shows the
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Figure 2 FTIR spectra of n-type CdS
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of the center frequency. The experi
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limit given by radiative relaxation
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from a long lifetime due to the pho
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are two natural approaches to study
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32. Inoshita, T.; Sakaki, H. Physic
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continuous spectral tunability over
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function and envelope function mome
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ottleneck’’ [14,28]. Further re
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in NQDs is dominated by nonphonon e
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Figure 4 Dynamics of the IR postpum
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Figure 5 (a) Time-resolved PL spect
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Figure 6 (a) The time delay of the
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and due to Auger-type e-h interacti
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Figure 9 Dynamics of the 1S bleachi
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significantly greater than the fast
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Figure 11 (a) Pump-intensity-depend
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NQD size. For small NQD sizes (R =
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Figure 14 Nonlinear absorption/gain
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sorption change associated with a s
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where n h em is the hole ‘‘emit
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ultrafast (subpicosecond to picosec
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Figure 18 Schematic of transitions
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Figure 19 Dynamics of pump-induced
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where n i (i=1, 2 . . . , N ) is th
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Figure 21 (a) Two-e-h-pair (biexcit
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the volume fraction (filling factor
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intensity dependence of this peak (
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can contribute to the saturation of
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coupling between ‘‘volume’’
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numerous discussions on the photoph
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53. Kang, K.; Kepner, A.; Gaponenko
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the ‘‘on-off ’’ emission in
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parallel form of data acquisition i
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Figure 3 (a) Spectral time trace of
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transition energies. In fact, these
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distribution (dark line) does not d
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exposure to only room light. In our
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statistics for the off times are in
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230Shimizu and BawendiCopyright 200
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Figure 10 (a) Time trace of a CdSe(
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and excited QD core states to fluct
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arrows indicate the on-time truncat
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W. K. Woo and V. C. Sundar for assi
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size allows the electron affinity a
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II.THEORY OF ELECTRON TRANSFER BETW
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For the specific case of charge tra
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dominates, the mobility is often fi
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where the constant A and the temper
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components of modulation which are
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nanocrystals [41], understanding ph
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and ionization potential through tw
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quantum dots. Furthermore, because
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For many applications, a host mater
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form blends with morphologies that
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Figure 11 Photoluminescence efficie
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Figure 12 (a) Room-temperature PIA
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discussed briefly in Section IV. Ch
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dithiolates to thiol-terminated DNA
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Films of passivated CdSe nanocrysta
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Figure 16 Photocurrent action spect
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decay with stretched exponential ki
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siderably larger than might be esti
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dispersing CdSe nanocrystal chromop
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memory and charge storage effects [
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all) of the optically excited elect
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composites of nanocrystals and conj
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55. Asbury, J.B.; Hao, E.C.; Wang,
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108. Morgan, N.Y.; Leatherdale, C.A
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The approaches to fabrication of se
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Figure 1 Experimental realization o
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Due to this voltage division, the m
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Figure 3 Simulated tunneling spectr
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electron charging. In both positive
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Figure 5 shows the typical features
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Figure 7 Map of levels for InAs nan
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Figure 8 Scanning electron microsco
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D CB = 0.31 eV is thus obtained. On
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Figure 11 Correlation of optical an
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atomistic approach based on pseudop
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charging indicated that the tunneli
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capacitance values were also kept t
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could not be detected in the QD/DT/
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Figure 18 Tunneling conductanceF sp
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data in the inset of Fig. 19 repres
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corresponding to the s-like wave fu
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7. Grabert, H.; Devoret, M.H., Eds.
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66. Su, B.; Goldman, V.J.; Cunningh
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dimensional confinement are created
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Figure 1 Transmission electron micr
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The room-temperature absorption and
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narrower in samples with larger mea
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GaInP 2 QDs from a plot of the squa
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crystal, indicating lattice-matched
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Figure 5 Evolution of Stranski-Kras
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Page 361 and 362: C. Efficient Anti-Stokes Photolumin
Page 363 and 364: Because HF treatment has been shown
Page 365 and 366: Copyright 2004 by Marcel Dekker, In
Page 367 and 368: intensity of the PL when it is on a
Page 369 and 370: eV stems from recombining carriers
Page 371 and 372: Figure 16 Model to explain two-colo
Page 373 and 374: although this term is not rigorousl
Page 375 and 376: 10 ps (about an order of magnitude
Page 377 and 378: electron relaxation is inhibited an
Page 379 and 380: Figure 18 Transmission electron mic
Page 381 and 382: QDs, the nature of the QD capping s
Page 383 and 384: QD solution. For an interdot distan
Page 385 and 386: emission spectra of the two individ
Page 387 and 388: Figure 23 Change of the PL intensit
Page 389 and 390: (viz. the absorbed light intensity)
Page 391 and 392: Figure 25Impact ionization in QDs.m
Page 393 and 394: prevent electron-hole recombination
Page 395 and 396: 36. Miller, R.D.J.; McLendon, G.; N
Page 397 and 398: 91. Vurgaftman, I.; Singh, J. Appl.
Page 399 and 400: 139. Mićić, O.I.; Ahrenkiel, S.P.
Page 401 and 402: 10Synthesis and Fabrication of Meta
Page 403 and 404: Figure 2 (A-C) Progression of HR-TE
Page 405 and 406: Figure 3 Schematic for gold nanocry
Page 407 and 408: Nanocrystal growth can occur by two
Page 409 and 410: on the other hand, provide an ensem
Page 411: Figure 6 (a) SAXS patterns for disp
Page 415 and 416: of the stabilizing ligand, and the
Page 417 and 418: successfully modeled the 2D island
Page 419 and 420: 2. Steric Stabilization and a Soft
Page 421 and 422: are fully extended. Moving away fro
Page 423 and 424: Figure 11 High-resolution SEM image
Page 425 and 426: Figure 13 (A) Transmission electron
Page 427 and 428: function of the density of localize
Page 429 and 430: Figure 15 High-resolution SEM image
Page 431 and 432: thiol-capped nanocrystals [2]. The
Page 433 and 434: 41. Ackerson, B.J. Nature 1993, 365
Page 435 and 436: with the effect of the particle com
Page 437 and 438: Figure 1a shows the surface plasmon
Page 439 and 440: Figure 2 (a) Ultraviolet-visible ab
Page 441 and 442: agents [34]. The short-wavelength b
Page 443 and 444: Figure 4 (a) Plot of the plasmon ab
Page 445 and 446: the framework of traditional Mie’
Page 447 and 448: show that effects due to the surrou
Page 449 and 450: is located at the position of the g
Page 451 and 452: Copyright 2004 by Marcel Dekker, In
Page 453 and 454: Figure 8 Ultraviolet-visible absorp
Page 455 and 456: laser pulses while being mixed in t
Page 457 and 458: Figure 10 shows HR-TEM images of go
Page 459 and 460: Figure 11 Transmission electron mic
Page 461 and 462: final irradiation product. At the s
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following the laser excitation appe
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36. Papavassiliou, G.C. Prog. Solid
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particles to expand. Because the he
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was frequency doubled in a 1-mm B-
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Figure 2 Frequency of the acoustic
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Figure 3 Change in radius (DR/R) ve
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In this model, the electrons couple
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Figure 5 Transient bleach data for
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Figure 7 (a) Transient bleach data
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that the particles with >80% Au hav
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3. Del Fatti, N.; Valle´e, F.; Fly
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