B21-P-02STEM observations of Au/SrTiO3catalysts

Abstract

Semiconductor nanoparticles, CdSe nanoparticles, with ~10 nm in diameter are applied for light emitting devices. Multi-shell nanoparticles, CdSe/CdS/ZnS nanoparticles (CdSe core particle covered by CdS innershell and ZnS outer shell) are synthesized to protect reactive CdSe core from environment and to improve high electron-hole recombination probability. However, the photo luminescent efficiency of multhshell nanoparticle does not always show improvement depending on the synthesizing conditions. To clarify an origin of the luminescent property, it is effective to evaluate dielectric properties of single nanoparticles by using EELS measurement. In this study, high energy-resolution EELS measurement of multishell nanoparticles was conducted by using the monochromator analytical TEM. Figure shows the comparison between experimental and simulated EELS spectra of a multishell nanoparticle. The simulation was based on the classical dielectric theory [1]. Since the photo luminescent properties should be reflected to the electronic structure around band gap region, spectral structures in energy loss < 5eV are investigated in detail. As a result, spectral structures attributed to interband transitions coming from core and shell could be observed and the intensity profile of the spectra was valid for the dielectric response of the multishell structure. Through the detail investigation of the spectra, dielectric property of single multishell nanoparticle is clarified and relation with the photo luminescent property will be discussed.