Nanocrystal growth

Peng Z G, Wickham J and Alivisatos A P 1998 Kinetics of ll-VI and lll-V colloidal semiconductor nanocrystal growth focusing of size distributions J. Am. Chem. Soc. 120 5343... 

Peng X, Wickham J, Ahvisatos AP (1998) Kinetics of 11-VI and III-V colloidal semiconductor nanocrystal growth Focusing of size distributions. J Am Chem Soc 120 5343-5344... 

Fig. 12.2 Ni(OH)2 nanocrystal growth on a graphene sheet (GS, upper) and graphite oxide sheet (GO, lower) with 5 % and 20 % oxygen content, respectively. Reprinted with permission from [47]. Copyright 2010, American Chemical Society.

The reaction can be followed by monitoring the characteristic absorption due to ZnO band-gap excitations, occurring at energies above 28,000 cm-1. The energy of the first excitonic transition depends on the nanocrystal size, and so provides a probe of nanocrystal growth. For a fixed size, the intensity of the transition provides a measure of the nanocrystal concentration (i.e., the yield of the chemical reaction), and this offers a measure of nucleation yields. 

The structure and composition of a nanocrystalline surface may have a particular importance in terms of chemical and physical properties because of their small size. For instance, nanocrystal growth and manipulation relies heavily on surface chemistry [261]. The thermodynamic phase diagrams of nanocrystals are strongly modified from those of the bulk materials by the surface energies [262]. Moreover, the electronic structure of semiconductor nanocrystals is influenced by the surface states that He within the bandgap but are thought to be affected by the surface reconstruction process [263]. Thus, a picture of the physical properties of nanocrystals is complete only when the structure of the surface is determined. 

Mintova, S, Olson, N.H., Valtchev. V., Bein, T. 1999. Mechanism of zeolite A nanocrystal growth from coUoids at room temperature. Science 283. 958-960... 

S, Mintova, N, H, Olson, V, Valtchev, and T. Bein. Mechanism of zeolite a nanocrystal growth from colloids at room temperature. Science, 283 958-960, 1999... 

Shape control can be directed by the use of molecular capping agents, which adsorb to specific crystal planes such that growth is limited on those crystal planes without capping molecules, or which have only weakly coordinated molecules. Surfactants, polymers and biomolecules, small gas molecules and even different metal ions have each been shown capable of controlling nanocrystal growth [219]. 

X. Peng, J. Wickham, A. P. Alivisatos, Kinetics of 11-Vl and 111-V CoUoidal Semiconductor Nanocrystal Growth Focusing of Size Distributions. Journal of the American Chemical Society 1998,120, 5343-5344. 

Water soluble CdTe was produced by reacting NaHTe drop-wise to argon-saturated Cd-3-mercaptopropionic acid (MPA) mixture. The CdTe quantum dots were synthesized at different molar ratios of precursors to probe the effect of capping material on nanocrystal growth. In addition there were systematic investigations of the pH, temperature and molar ratios of precursors on the crystal growth and luminescent properties. 

Salzemann C, Lisiecki I, Urban J, Pileni MP. Anisotropic copper nanocrystals synthesized in a supersaturated medium nanocrystal growth. Langmuir... 

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