GdF3∶Eu3+/NaGdF4∶Eu3+纳米晶的水热合成及发光性质

采用水热法,以聚乙二醇(400)为分散剂,以NaOH和HNO3溶液调节初始溶液pH值,合成GdF3∶Eu3+和NaGdF4∶Eu3+纳米晶。XRD和SEM结果表明:在酸性溶液(pH=3,5)、中性溶液(pH=7)和碱性溶液(pH=9)中,分别获得具有正交结构的GdF3∶Eu3+纳米晶,GdF3∶Eu3+和NaGdF4∶Eu3+混合晶,六方结构NaGdF4∶Eu3+棒状微米晶。根据Scherrer公式估算pH=3和pH=5时制备纳米晶的一次性粒径分别为49和28 nm。样品的发射光谱结果表明:特征发射峰来自于5D2、5D1、5D0到7FJ跃迁。在主晶相为GdF3样品中,主发射峰来自于Eu3+的5D0→7F1的磁偶极跃迁;晶相为NaGdF4样品的主发射峰来自于Eu3+的5D0→7F2电偶极跃迁。5D0→7F1和5D0→7F2跃迁发射相对强度比值显示:Eu3+在NaGdF4晶体中的格位对称性下降。激发光谱显示出Gd3+和Eu3+具有较好的能量传递。

Hydrothermal Synthesis and Luminescence Properties of GdF3:Eu3+/NaGdF4:Eu3+Nanocrystals

GdF3∶Eu3+/NaGdF4∶Eu3+ nanocrystals were prepared by a hydrothermal method in a solution with pH value adjusted by dilute NaOH and HNO3 solution using polyethylene glycol as dispersing agent.The results of XRD and SEM indicate that orthorhombic GdF3 nanocrystals,GdF3 and NaGdF4 mixed nanocrystals,hexagonal NaGdF4 microcrystals with rod-like shape could be obtained in the acidic(pH=3,5),neutral(pH=7) and alkaline(pH=9)solution,respectively.The average crystallite size as estimated by Scherrer equation is 49 nm and 28 nm for nanocrystals prepared in the initial solution with pH value of 3 and 5,respectively.The results of emission spectra show that the emission peaks are ascribed to 5D2、5D1、5D0-7FJ transition.The magnetic dipole transition originated from 5D0→7F1 of Eu3+ is the strongest in the samples with GdF3 as the main phase,the main emission of NaGdF4 is from the electric dipole transition originated from 5D0→7F2 of Eu3+.The 5D0-7F1/5D0-7F2 relative emission intensity ratios show the lattice symmetry of Eu3+ in NaGdF4 crystals declines.The results of excitation spectra exhibit an efficient energy transfer from Gd3+ to Eu3+.