Optical properties of Nd3+ ion-doped ZnO nanocrystals.

Hexagonal Nd(3+)-doped ZnO nanocrystals with multiple luminescent centers were synthesized by means of a facile sol-gel method. The Nd(3+)-doped ZnO nanocrystals were characterized by using the X-ray diffraction, transmission electron microscopy, ultraviolet-visible reflectance spectra, and fluorescence spectroscopy. Host-to-Nd3+ energy transfer was observed for the first time in Nd(3+)-doped ZnO nanocrystals. It was found that Nd3+ ions can be effectively sensitized by the ZnO nanocrystals, resulting in sharp and intense characteristic Nd3+ luminescence. The photoluminescence (PL) and PL excitation spectra of Nd3+ ions in the ZnO nanocrystals were investigated in detail. Furthermore, the possible mechanism of host-to-Nd3+ energy transfer was also proposed on the basis of the optical properties of Nd3+ ions in the ZnO nanocrystals.