In the paper

we report the optical properties of CdS semiconductor ultrafine particles in hydrosols and those of CdS semiconductor ultrafine particles in organosols in which the surfaces of the particles are coated with a layer of organic surfactant molecules. The experimental results show that surface modification of the particles significantly affects their optical properties.CdS hydrosols and organosols were prepared through colloidal chemical method. The particle size and size distribution were determined by TEM and small angk X-ray scattering. The results show that the colloidal particle size is below 10nm.The absorption

excitation and emission spectra of CdS particles in the hydrosols and organosols were measured and discussed

we conclude that when the particle size is less than 5nm

the particles exhibit obvious quantum size effects.The surface modification of the particles effectively removes the surface defects of the particles

and strongly enhances the intensity of interband luminescence. On the other hand

a number of discrete electronic transitions due to quantum confinement effects are observed and explained by the effective mass approximation.