Metal nanocrystals

Dodecanethiol-capped Ag nanocrystals, prepared by the Brust method self-assemble into two-dimensional arrays (see Fig. 3.7) [156]. From the separation distance of 1.5 nm seen between the nanocrystal surfaces, one can deduce that the alkane chains projecting out of neighboring nanocrystals are inter-digitated. The ordered arrangement of nanocrystals typically covers an area of several square microns. Thiol-capped Au nanocrystals prepared by the Brust method have been size-fractionated in order to organize into well-ordered two-dimensional arrays [581]. Two-dimensional arrays of noble metal nanocrystals 

In addition to alkanethiols, long-chain fatty acids are used for ligating and assembling metal nanocrystals. A colloidal dispersion of Co nanocrystals capped with fatty acids self-assembles to yield hexagonally ordered arrays similar to those obtained with alkanethiols [162,590]. Ag nanocrystals capped with fatty acids of appropriate lengths yield cubic or hexagonal close-packed 

Au and Ag nanocrystals of different sizes have been reported [599]. An AB type of superlattice has been obtained starting with oleic acid-capped Fe and dodecanethiol-capped Au nanocrystals [600]. 

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Markovich G, Collier C P and Heath J R 1998 Reversible metal-insulator in ordered metal nanocrystal... 

Fig. 4. (a) Ni nanociystals formed on HfOj after sputtering followed by annealing and (b) AES analysis of the elemental composition of the islands and matrix suggested well separated metal nanocrystals. 

Pol VG, Grisaru H, Gedanken A (2005) Coating noble metal nanocrystals (Ag, Au, Pd and Pt) on polystyrene spheres via ultrasound irradiation. Langmuir 21 3635-3640... 

Xia, Y., Xiong, Y., Lim, B., and Skrabalak, S.E. (2009) Shape-controlled synthesis of metal nanocrystals simple chemistry meets complex physics Angewandte Chemie International Edition, 48 (1), 60-103. 

On the other hand, the inclusion of electrocatalytically active metal nanocrystals (graphite-supported palladium, platinum, and ruthenium or gold nanocrystals) allowed... 

Jana, N. R. Peng, X. 2003. Single-phase and gram-scale routes toward nearly monodisperse Au and other noble metal nanocrystals. J. Am. Chem. Soc. 125 14280-14281. 

Semiconductor and Metal Nanocrystals Synthesis and Electronic and Optical Properties, edited by Victor I. Klimov... 

OF-KEDF s with the DD AWF emerged, " and a scheme to treat highly inhomogeneous systems like realistic surfaces was tested with semiquantitative success. " An immediate application to the study of the metal-insulator transition in a 2-dimensional array of metal nanocrystal quantum dots (with 498 A1 atoms per simulation cell) further magnifies its promise. ... 

However, transition from discrete to a continuous spectrum of levels does not mean full disappearance of quantum dimensional effects. It has been shown [14] that even in rather large metal nanocrystals in the size 5-10 nm it is necessary to take into account the direct influence of crystal boundaries on density of the crystal electronic levels that leads to the dependence of Fermi energy on the crystal size. The Fermi energy correction for a spherical crystal caused by crystal surface is inversely proportional to radius of crystal... 

The nanocrystals of such type form in various liquid media, such as organic solution [77, 81] or the softened quasi-liquid glass [82, 83], where there are no steric hindrances for the growth of equilibrium crystals without surface defects. At the same time, barriers for aggregation of clusters or atoms to metal nanocrystals in solid system that arises during the cryochemical solid-state synthesis favor the formation of crystals with structural defects,... 

Similar histograms were determined by TEM for Pb-, Zn-, and Cd-containing nanocomposite PPX films prepared by vapor deposition cryochemical synthesis [85]. The value d of metal nanocrystals in these films is also 5nm. The same approximately size d ( 4.5nm) has been evaluated from Ai/2 of X-ray diffraction peak for semiconductor PbS nanocrystals in PbS-PPX nanocomposite [71]. It should be particularly emphasized that d value of M/SC nanocrystals embedded by cryosynthesis in PPX and C1PPX matrices does not depend on M/SC content as for low loading (0.2-2 vol.% for Ag in PPX and C1PPX [75, 80] and 0.01-1 vol.% for Pb in PPX [85]) and for high loading (5-11 vol.% for PbS in PPX [3, 71, 86]) systems. 

S. Link, M. A. El-Sayed, in Semiconductor and Metal Nanocrystals Synthesis and Electronic and Optical Properties (Ed V. I. Klimov), New York Routledge, 2003,421-452. 

Tao AR, Habas S, Yang P. Shape control of colloidal metal nanocrystals. Small 2008 4 310-25. 

Link S, El-Sayed MA. Optical properties and ultrafast dynamics of metallic nanocrystals. Anna Rev Phys Chem 2003 54 331-66. 

Extensive investigations of metal nanocrystals of various sizes obtained, for example by the deposition of metals on amorphised graphite and other substrates, by X-ray photoelectron spectroscopy and related techniques 4-51 have yielded valuable information on their electronic structure. An important result from these experiments is that as the metal particle size decreases, the core-level binding energy of metals such as Au, Ag, Pd, Ni and Cu increases sharply. This is shown in the case of Pd in Figure 2, where the binding energy... 

Chemical reactivity The surface area of nanocrystals increases markedly with the decrease in size. Thus, a small metal nanocrystal of 1 nm diameter will have —100% of its atoms on the surface. A nanocrystal of 10 nm diameter on the other hand, would have only 15 % of its atoms on the surface. A... 

Magic Nuclearity Giant Clusters of Metal Nanocrystals Formed by Mesoscale Self-Assembly... 

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