Tong Chao, Xie Shaowen, Zhou Hu, Li Na, Gong Liang, Jian Jian, Zhang Changfan, Xu Lijian, Xu Jianxiong
Hunan Key Laboratory of Biomedical Nanomaterials and Devices, College of Life Sciences and Chemistry, Hunan University of Technology, Zhuzhou 412007, P. R. China.
Key Laboratory of Theoretical Organic Chemistry and Function Molecule, Ministry of Education, Hunan Provincal Key Laboratory of Controllable Preparation and Functional Application of Fine Polymers, School of Chemistry and Chemical Engineering, Hunan University of Science and Technology, Xiangtan, 411201, China.
J Nanosci Nanotechnol. 2018 Dec 1;18(12):8258-8268. doi: 10.1166/jnn.2018.16384.
In this study, well-defined PAA-coated NaYF4:Yb3+, Er3+ nanophosphors were synthesized via a poly(acrylic acid) (PAA) mediated hydrothermal process. The rational control of initial reaction conditions, such as hydrothermal temperature, pH value of precursor-solution, added amount of PAA, and molecular weight of PAA ligand, resulted in upconversion of NaYF4:Yb3+, Er3+ phosphors with varying crystal phases (α and β) and morphologies (e.g., nanosphere, submicrorod, microrod, microtube, and microprism). By assessing the upconversion luminescent properties of the synthesized NaYF4:Yb3+, Er3+ phosphors upon excitation by 980 nm infrared light, it was demonstrated that the β-phase NaYF4:Yb3+, Er3+ phosphors generally presented stronger upconversion luminescent than α-phase NaYF4:Yb3+, Er3+ phosphors and orthorhombic phase of YF3:Yb3+, Er3+ sample. Additionally, the β-phase NaYF4:Yb3+, Er3+ phosphors with hollow microtube morphology presented higher upconversion luminescent intensity than phosphors of other morphologies. This may be due to microtubes having larger surface area (inner and outer surfaces), which promoted the absorption efficiency under similar excitation conditions, therefore generating higher luminescent intensity. Findings form this study suggest for precisely controlled growth of other complex rare earth fluoride compounds and provide a reference for exploration of component-, phase- and morphology-dependent upconversion luminescence properties.
在本研究中，通过聚丙烯酸（PAA）介导的水热法合成了定义明确的PAA包覆的NaYF4:Yb3+、Er3+纳米磷光体。对初始反应条件进行合理控制，如水热温度、前驱体溶液的pH值、PAA的添加量以及PAA配体的分子量，可使NaYF4:Yb3+、Er3+磷光体发生上转换，形成具有不同晶相（α和β）和形貌（如纳米球、亚微米棒、微米棒、微管和微棱镜）的产物。通过评估合成的NaYF4:Yb3+、Er3+磷光体在980 nm红外光激发下的上转换发光特性，结果表明，β相NaYF4:Yb3+、Er3+磷光体的上转换发光通常比α相NaYF4:Yb3+、Er3+磷光体以及YF3:Yb3+、Er3+样品的正交相更强。此外，具有中空微管形貌的β相NaYF4:Yb3+、Er3+磷光体的上转换发光强度高于其他形貌的磷光体。这可能是由于微管具有更大的表面积（内表面和外表面），在相似的激发条件下提高了吸收效率，从而产生更高的发光强度。本研究结果为精确控制其他复杂稀土氟化物化合物的生长提供了思路，并为探索成分、相和形貌依赖的上转换发光特性提供了参考。
