Size Quantization Effect

Henglein A 1988 Mechanism of reactions on colloidal microelectrodes and size quantization effects Top. Curr. Chem. 143 115... 

Mechanism of Reactions on Colloidal Microelectrodes and Size Quantization Effects... 

Lead(II) sulfide occurs widely as the black opaque mineral galena, which is the principal ore of lead. The bulk material has a band gap of 0.41 eV, and it is used as a Pb " ion-selective sensor and IR detector. PbS may become suitable for optoelectronic applications upon tailoring its band gap by alloying with II-VI compounds like ZnS or CdS. Importantly, PbS allows strong size-quantization effects due to a high dielectric constant and small effective mass of electrons and holes. It is considered that its band gap energy should be easily modulated from the bulk value to a few electron volts, solely by changing the material s dimensionality. 

Baral S, Fojtik A, Weller H, Henglein A (1986) Photochemistry and radiation chemistry of coUoidal semiconductors. 12. Intermediates of the oxidation of extremely small particles of cadmium sulfide, zinc sulfide, and tricadmium diphosphide and size quantization effects (a pulse radiolysis study). J Am Chem Soc 108 375-378... 

Size Quantization Effects in Semiconductor Particles 5.1 General Remarks... 

Strong size quantization effects were found for lead sulfide While the sulfide... 

In addition to this size quantization effect, a second effect was observed in the reaction of OH with Q-CdS. As is seen from Fig. 20, oscillations occur in the difference spectrum of the product at wavelengths below the absorption threshold. The absorptions in this wavelength range are not caused by the positive holes but are due to the changes in size of the colloidal particles upon OH attack. The absorption spectrum shifts slightly towards shorter wavelengths as the particles become smaller in reacting... 

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