Quantum crystallites

Brus L E 1993 NATO ASI School on Nanophase Materials ed G C Had]lpanayls (Dordrecht Kluwer) Allvisatos A P 1996 Semiconductor clusters, nanocrystals and quantum dots Science 271 933 Heath J R and Shlang J J 1998 Covalency In semiconductor quantum dots Chem. See. Rev. 27 65 Brus L 1998 Chemical approaches to semiconductor nanocrystals J. Phys. Chem. Solids 59 459 Brus L 1991 Quantum crystallites and nonlinear optics App/. Phys. A 53 465... 

Bawendi M G ef a/1992 Luminescence properties of CdSe quantum crystallites resonance between interior and surface localized states J. Chem. Phys. 96 946... 

Kortan AR, Hull R, Opila RL, Bawendi MG, Steigerwald ML, Carroll PJ, Brus LE (1990) Nucleation and Growth of Cdse on Zns Quantum Crystallite Seeds, and Vice Versa, in Inverse Micelle Media. J Am Chem Soc 112 1327-1332... 

Brus, L. Radiationless transitions in CdSe quantum crystallites, lsr. J. Chem. 1993, 33, 9. 

Kortan A R, Hull R and Opila R L 1990 Nucleation and growth of CdSe on ZnS quantum crystallite seeds and vice versa in inverse micelle media J. Am. Chem. Soc. 112 1327... 

Brus L 1991 Quantum crystallites and nonlinear optics Appl. Phys. A 53 465... 

Kanemoto M, Shiragami T, Pac CJ, Yanagida S Semiconductor photocatalysis — effective photoreduction of carbon-dioxide catalyzed by ZnS quantum crystallites with low-density of surface-defects. J Phys Chem 1992, 96(8) 3521— 3526. 

Yanagida S, Yoshiya M, Shiragami T, Pac CJ, Mori H, Fujita H Semiconductor photocatalysis. 9. Quantitative photoreduction of aliphatic ketones to alcohols using defect-free ZnS quantum crystallites. J Phys Chem 1990, 94(7) 3104— 3111. 

Braunstein P, Oro G, Raithby PR (eds) (1999) Metal clusters in chemistry. Wiley-VCH, Weinheim Brus L (1991) Quantum crystallites and nonlinear optics. Appl Phys A 53 465-474... 

The Si nanocrystals exhibit photoluminescence upon irradiation with UV light at 230 nm. The MPL spectrum is shown in Figure 10. The spectrum is similar to that reported for 4 nm Si nanocrystals upon excitation with 350 nm at 20 K and also to that PL spectrum of Porous Silicon (49). In these systems the red luminescence is interpreted as a consequence of quantum crystallites which exhibit size-dependent, discrete excited electronic states due to a quantum effect (6,50,51). This quantum confinement shifts the luminescence to higher energy than the bulk crystalline Si (1.1 eV) band gap. This indirect gap transition is dipole forbidden in the infinite preferred crystal due to translational symmetry. By relaxing this symmetry in finite crystallite, the transition can become dipole allowed. As pointed out by Brus (49), the quantum size effect in Si nanocrystals is primarily kinetic mainly due to the isolation of electron-hole pairs from each other. 

Characterization and Surface Chemistry. Thus obtained quantum crystallites have been characterized by various techniques. Figure 3 shows a high resolution transmission electron micrograph (HRTEM) of GaP nanocrystallites. Numerous lattice fringes... 

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