Quantum confinement effect in nanocomposites

Composites of nanometer-sized metal particles within a dielectric medium ha ve attracted a lot of attention in recent years because of interesting prop erties exhibited by them. Quantum confinement effect tend to dominate the p roperties of carriers within the particles having nanoscale dimensions. Nan ocomposites have been prepared by simple chemical methods. Optical absorpti on data when analyzed with Mie's scattering formula give results which indi cate a metal-insulator type transition in the case of silver particles havi ng diameters around 3 nm. Heterostructure quantum dots involving Ag2O nanop articles with a thin shell of metallic silver show unusual optical absorpti on spectra again arising due to a confinement effect. Composites consisting of the ferroelectric phase BaTiO3 and nanosized nickel or silver, in a gel medium show a large increase in the value of dielectric permittivity. This is explained as resulting from a quantum size effect. (C) 2001 Elsevier Sc ience B.V. All rights reserved.