Size Control of CdS Quantum-confined Ultrafine Particles by Photocatalytic Polymer Coating

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Abstract
CdS quantum-confined ultrafine particles (Q-ufp) were prepared in colloidal solutions in the presence of styrene monomer under photoirradiation. By means of transmission electron microscopy analysis, it has been experimentally verified for the first time that the prepared CdS Q-ufp were coated with polystyrene layer, and the particle size distribution was controlled by selecting the wavelength of the irradiating laser light: shorter wavelength light irradiation gave smaller CdS Q-ufp. A mechanism for particle size control through photocatalytic polymer coating is discussed to explain the experimental results; the particle size distribution or corresponding UV-vis absorption spectra were simulated using the proposed model. As a result, the oxidation potential of styrene monomer, relative to the highest occupied molecular orbital (HOMO) or the top of the valence band of CdS Q-ufp which depends on the particle size, is important for electron transfer necessary for initiating the polymer coating process.