Three-dimensional (3D) self-assembled hierarchical bismuth oxide architectures were prepared via a solution precipitation synthesis at 85 degrees C in 45 min with the aid of polyethylene glycol-8000 (PEG-8000) as a capping agent. The morphology and crystalline phase evolution was studied versus reaction time and capping agent concentration and interpreted in terms of growth mechanisms. At higher capping agent concentrations, the as-grown 3D hierarchical flowerlike bismuth oxide was crystalline cubic gamma-phase that was previously formed only at temperature > or =640 degrees C. The morphology and crystal structure of these 3D cubic gamma-phase bismuth oxide flowers were not changed with calcining up to 600 degrees C. Photoluminescence was attributed to emission from the Bi(3+) ion by a (3)P(0),(1) --> (1)S(0) transition and from defects. The gamma-phase flowerlike bismuth oxide shows better ion conductivity than that of rodlike bismuth oxide formed without the capping agent. The flowerlike morphology was attributed to modification of the nucleation and growth kinetics by the capping agent.

The effects on the luminescent properties of coating CdSe quantum dots with silica are presented. Coating increased the quantum yields from ∼10%–20% to ∼80% at a maximum. The changes in quantum yields and photoluminescence peak at wavelength were discussed in terms of the effects of surface charge. By neutralizing surface charge, the emission from CdSe quantum dots was initially blueshifted followed by redshifting, and the quantum yield increased dramatically.

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