Quantum size

A very different nucleation scheme by Grieser and co-workers employs ultrasonic irradiation of salt solutions to create H- and OH- radicals in solution [73]. These radicals proceed to nucleate growth of quantum-sized (Q-state) particles of cadmium sqlfide. Similar initiation has been used for polymer latices [74]. 

Rossetti R, Nakahara S and Brus L E 1983 Quantum size effects In the redox potentials, resonance Raman spectra and electronic spectra of CdS crystallites In aqueous solution J. Chem. Phys. 79 1086... 

Mittleman D M ef a/1994 Quantum size dependence of femtosecond electronic dephasing and vibrational dynamics in CdSe nanocrystals Phys. Rev. B 49 14 435... 

Quantum efficiencies Quantum efficiency Quantum electronics Quantum fluids Quantum mechanics Quantum size effect Quantumwell... 

Band gap engineetring confined hetetrostruciutres. When the thickness of a crystalline film is comparable with the de Broglie wavelength, the conduction and valence bands will break into subbands and as the thickness increases, the Fermi energy of the electrons oscillates. This leads to the so-called quantum size effects, which had been precociously predicted in Russia by Lifshitz and Kosevich (1953). A piece of semiconductor which is very small in one, two or three dimensions - a confined structure - is called a quantum well, quantum wire or quantum dot, respectively, and much fundamental physics research has been devoted to these in the last two decades. However, the world of MSE only became involved when several quantum wells were combined into what is now termed a heterostructure. 

D. Schmicker, T. Hibma, K. A. Edwards, P. B. Howes, J. E. MacDonald, M. A. James, M. Breeman, G. T. Barkema. Low-temperature growth of thin Pb layers and the quantum size effect. J Phys Condens Matt 9 969, 1997. 

Gorer S, Hodes G (1994) Quantum size effects in the study of chemical solution deposition mechanisms of semiconductor films. J Phys Chem 98 5338-5346... 

Hodes G, Albu-Yaron A, Decker F, Motisuke P (1987) Three-dimensional quantum-size effect in chemically deposited cadmium selenide films. Phys Rev B 36 4215-4222... 

Thin film coatings of nanocrystalline semiconductors, as collections of quantum dots (QD or Q-dot) attached to a solid surface, resemble in many ways semiconductor colloids dispersed in a liquid or solid phase and can be considered as a subsection of the latter category. The first 3D quantum size effect, on small Agl and CdS colloids, was observed and correctly explained, back in 1967 [109]. However, systematic studies in this field only began in the 1980s. 

Katsikas L, Eychmuller A, Giersig M, WeUer H (1990) Discrete excitonic transitions in quantum-sized CdS particles. Chem Phys Lett 172 201-204... 

Vogel R, Pohl K, Weller H (1990) Sensitization of highly porous, polycrystalline Ti02 electrodes by quantum sized CdS. Chem Phys Lett 174 241-246... 

Vogel R, Hoyer P, WeUer H (1994) Quantum-sized PbS, CdS, AgiS, SbiSs, and BiiSs particles as sensitizers for various nanoporous wide-bandgap semiconductors. J Phys Chem 98 ... 

Daniel, M.-C. and Astruc, D. (2004) Gold nanopartides assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology. Chemical Reviews, 104, 293-346. 

Zhou, H.S., Honma, 1., Komiyama, H. and Haus, J.W. (1994) Controlled synthesis and quantum-size effect in gold-coated nanoparticles. Physical Review B - Condensed Matter, 50, 12052-12057. 

Semiconductor nanoparticles have been intensively studied because of their properties of quantum size effects [54]. A number of synthetic techniques have been reported and their characteristics have been studied by various spectroscopic methods [55, 56]. However, magnetic field effects (MFEs) on the photoelectrochemical properties of semiconductor nanocrystals had not until now been reported. 

The nature of the element under investigation is certainly of some relevance, but not decisive for related elements, say noble metals. On the other hand, it is still not yet known how far the properties of two metal nanoparticles of different elements, but identical size really differ with respect to their quantum size behaviour. 

Bimetallic nanoparticles (including monometallic ones) have attracted a great interest in scientific research and industrial applications, owing to their unique large sur-face-to-volume ratios and quantum-size effects [1,2,5,182]. Since industrial catalysts usually work on the surface of metals, the metal nanoparticles, which possess much larger surface area per unit volume or weight of metal than the bulk metal, have been considered as promising materials for catalysis. 

Main obstacle in identifying quantum-size effects as a reason for structure sensitivity stems from the difficult discrimination from geometric influences the latter will be discussed in the next paragraph. 

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