Preparation and Photoluminescent Properties of Ce3+-Activated LaPO4 Nanocrystals and Core/Shell Structure
LI Zhen-ya, HUANG Shi-ming*, GU Mu, LIU Xiao-lin
Shanghai Key Laboratory of Special Artificial Microstructure Materials & Technology，School of Physics Science and Engineering，Tongji University，Shanghai 200092, China
Abstract：Hydrophobic, monodisperse LaPO4∶Ce3+ nanoparticles, LaPO4∶Ce3+/LaPO4 and LaPO4∶Ce3+/LaPO4∶Ce3+/LaPO4 core/shell structure nanocrystals were synthesized via a high-temperature organic solution approach. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PL). The results show that: all the samples are a monoclinic phase, Because of the size small nanoparticles, the diffraction peaks of the sample occurs width phenomenon. The LaPO4∶Ce3+ nanocrystals exhibits the characteristic emission of Ce3+ ions, the photoluminescence intensity increases first and then decreases with the increasing doping concentration of Ce3+ ions , and the best doping amount is 6 at%, with the increasing doping amount, the photoluminescence intensity decreases which may caused by the concentration quenching. Compared to LaPO4∶Ce3+ nanoparticles, the photoluminescence intensity of LaPO4∶Ce3+/LaPO4 and LaPO4∶Ce3+/LaPO4∶Ce3+/LaPO4 core/shell structure nanocrystals improves about 41% and 95% respectively, this may be a synergy of larger particle size of nanocrystals and surface passivation effect. FTIR spectra data shows that the absorption peak at 1 545 and 1 461 cm-1 corresponded to the asymmetric and symmetric stretching vibration of —COO-, the separation, Δ, between the two peaks is 84 cm-1, The mechanism of the sample surface modification by the organics might be that the oxygen atoms of the carboxyl are coordinated with the lanthunum ions by a bidentate mode.
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