Clusters quantum size effects

There are families of metal cluster compounds (Fig. 6.40) containing metal clusters surrounded by ligands (Lewis Green, 1982). In small cluster compounds, the electrons are paired, but in large clusters there will be closely spaced electronic levels, as in metal particles. In such clusters, quantum size effects would be expected. Benfield et al (1982) have found intrinsic paramagnetism in H20sio(CO)24 below 70K as expected of an osmium particle of approximate diameter of 10 A the excess paramagnetism increases with cluster size in osmium compounds (Johnson et al, 1985). 

Small gold clusters (<100 atoms) have become the subject of interest because of their use as building blocks of nanoscale devices and because of their quantum-size effects and novel properties such as photoluminescence, magnetism, and optical activity [427]. 

Model calculations for the Cs suboxides in comparison with elemental Cs have shown that the decrease in the work function that corresponds to an increase in the Fermi level with respect to the vacuum level can be explained semi-quantitatively with the assumption of a void metal [65], The Coulomb repulsion of the conduction electrons by the cluster centers results in an electronic confinement and a raising of the Fermi energy due to a quantum size effect. 

Wang Y, Herron N (1991) Nanometer-sized semiconductor clusters material synthesis, quantum size effects, and photophysical properties. J Phys Chem 95 525-532 Ward MH, Cantor KP, Riley D, Merkle S, Lynch CF (2003) Nitrate in public water supplies and risk of bladder cancer. Epidemiology 14 183-190 Ward MH, Mark SD, Cantor KP, Weisenburger DD, Correa-VUlasenore A, Zahm SH (1996) Drinking water and the risk of non-Hodgkin s lymphoma. Epidemiology 7 465 71 Warheit DB (2004) Nanoparticles health impacts Mater Today 7 32-35... 

Wang Y, Herron N (1991) Nano-meter sized semiconductor clusters, materials synthesis and quantum size effects, and photophysical properties. J Phys Chem 95 525-532... 

A colloid chemical approach to CdS/HgS/CdS spherical quantum wells was described [79]. Size-dependent third-order non-linear susceptibilities of CdS clusters were investigated [80]. Reviews appeared on size-quantized nanocrystalline semiconductor films [81] and on the quantum size effects and electronic properties of semiconductor microcrystallites [82]. 

Wang Y., Herron N. (1991) Nanometer-Sized Semiconductor Clusters Materials Synthesis, Quantum Size Effects and Photophysical Properties, J. Phys. Chem. 95(2) 525-532. 

Wang Y,Herron N. Nanometer-sized semiconductor clusters materials synthesis, quantum size effects, and photophysical properties../ Rhys Chem 1991 95 525. 

It is important that much the data relate to the case when the active component particles cannot be treated as clusters of atoms and that need strict consideration of the quantum size effects, but as a continuous phase with the properties described by standard methods of the continuous phase thermodynamics. Inspection of these experimental data reveals that... 

We calculated the electronic structure of 1-D, 2-D, and 3-D silicon clusters using (DV)-Xa MO method. The calculated energy gap Eg) between HOMO and LUMO decreases with increase of the cluster size and the number of dimensions of the cluster. It is found that including silicon 3d orbitals as basis sets results in lowering the Eg values by about leV. The results also show that the components of silicon 3d orbitals in the unoccupied levels near LUMO axe over 50%. In the case of silicon clusters, the size effect on the Eg value is well described by the quantum-well(QW) model in which the delocalized wavefunc-tions are confined in the potential well. The calculated results predict that Eg... 

Raman spectra gave evidence for quantum size effects in CdS clusters confined in zeolite pores.433 The Raman spectra of nanocrystals of CdSi xSex... 

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