摘要
用水热法合成了稀土掺杂的立方相、六方相NaYF4:Eu3+和正交相YF3:Eu3+纳米晶体.从立方相到六方相NaYF4:Eu3+仅仅通过改变前驱物的浓度来实现,而改变RE3+/NaF的比例,则得到正交相YF3:Eu3+纳米晶体.通过分析XRD,TEM和荧光探针离子Eu3+的荧光发射谱,详细研究了前驱物浓度控制的纳米晶体的生长机理,并用光谱学手段评价了结晶的好坏.为了进一步完善结晶程度和除去纳米晶体表面的羟基团,将立方相、六方相NaYF4:Eu3+和正交相YF3:Eu3+纳米晶体退火处理,发现六方相NaYF4:Eu3+结构是一种热力学稳定相,而立方相NaYF4:Eu3+和正交相YF3:Eu3+则容易相变为YOF:Eu3+,退火之后的样品均表现出一定程度的团聚.将Tb3+离子掺杂于3种氟化物基质中,研究其荧光特性,发现在YF3:Tb3+纳米晶体中,晶场劈裂明显,甚至在室温下,可以清晰的观察到斯托克斯劈裂.这进一步揭示了减少NaF的量,可以有效地控制生长速率,导致结晶发育良好.
Cubic phase, hexagonal phase NaYF4 ： Eu3＋ and orthogonal phase YF3 ： Eu3＋ nanocrystals were prepared using a mild hydrothermal method. Transition from cubic phase to hexagonal phase NaYF4 ： Eu3＋ nanocrystals was realized only by simply changing the concentrations of starting materials, and orthogonal-phase YF3 ： Eu3＋ nanocrystals were also synthesized by varying the ratio of rare-earth ions to sodium fluoride. X-ray diffraction （XRD）, transmission electron microscopy （TEM） and fluorescence spectroscopy were used to investigate the grown mechanism of nanocrystals controlled by precursor concentrations in detail and the crystallinity was evaluated by spectroscopic approach as well. To further improve crystallinity and eliminate the hydroxyl at the surface of nanocrystals, we have treated the cubic phase, hexagonal phase NaYF4 ： Eu3＋ and orthogonal phase YF3 ： Eu 3＋ nanocrystals by annealing. Results showed that hexagonal phase NaYF4 ： Eu3＋ nanocrystals are stabilized in thermodynamics and the phase transitions from cubic phase NaYF4 ： Eu3＋ and orthogonal phase YF3 ： Eu3＋ to hexagonal phase YOF nanocrystals are easy to happen. The samples after sintering treatment are all agglomerate to some extent. Photoluminescence properties of Tb3＋ ions doped these three fluoride matrices showed that the crystal-field splitting was obviously observed in YF3 ： Tb3＋ nanocrystals, even at room temperature, which revealed that we can effectively control the growing speed by reducing the content of sodium fluoride, leading to crystalline grow well.
出处
《中国科学：物理学、力学、天文学》
CSCD
北大核心
2013年第1期23-30,共8页
Scientia Sinica Physica,Mechanica & Astronomica
基金
教育部"春晖计划"研究项目资助(编号:Z2010067)
关键词
水热法
纳米晶体
相变
荧光特性
hydrothermal method
nanocrystals
phase transition
optical property
