Morphological control and luminescent properties of YVO4:Eu nanocrystals.

Rodlike, olivelike, pineapplelike, and particlelike nanocrystals of theYVO4:Eu (5 at. % Eu) were synthesized by a hydrothermal reaction with different conditions, respectively. The rodlike nanocrystal has a rectangular cross-section with about 35 x 60 nm2 and a length of about 220 nm. The olivelike nanocrystal has an equatorial diameter of approximately 40 nm and a length of approximately 200 nm. The pineapplelike nanocrystal with an equatorial diameter of approximately 200 nm and a length of approximately 300 nm, is a superstructure consisting of self-organized nanorods with a diameter of approximately 20 nm and a length of approximately 50 nm. The particlelike nanocrystals show globular and polyhedral shape with a diameter of approximately 50 nm. Their UV-vis absorption peaks are at 305, 308, 285, and 280 nm, respectively, and there is such a trend that the absorption peaks shift to higher energy as the size of the particles decreases. Compared with other-shape nanocrystals, the luminescence intensity of the olivelike nanocrystals is obviously enhanced. It suggests that we could obtain the function-improved materials by tailoring the size and shape of theYVO4:Eu nanostructures.