Preparation of Highly Luminescent Semiconductor Nanoparticles for the Application of White-Light-Emitting Devices

Abstract

The photoluminescent properties of silica-coated cadmium selenide (SiO₂/CdSe) nanoparticles was modified by using the size-selective photoetching technique. The irradiation of laser light caused the blue shift of the absorption spectra of SiO₂/CdSe and finally the absorption onset agreed with the wavelength of irradiation light. These facts indicated that CdSe particles were photoetched to smaller ones until the irradiated photons were not absorbed by the photoetched particles and that the SiO₂ shell layer surrounding the CdSe core prevented coalescence between the photoetched particles. The application of size-selective photoetching to SiO₂/CdSe resulted in the development of the band gap emission, the degree being enhanced with progress of the photoetching. The peak wavelength of photoluminescence was blue-shifted with decrease in the wavelength of laser light used for the photoetching. The size selective photoetching could be applied to control the photoluminescence wavelength of the SiO₂/CdS particles immobilized on a glass substrate, and the partial photoetching of SiO₂/CdSe nanoparticle films produced intense band gap emission of CdSe at the photoetched area, resulting in the formation of a clear photoluminescence image under UV irradiation. This technique makes it possible to produce a multicolor photoluminescence image by irradiation with monochromatic lights having various wavelengths using a single source material.