Li Anming, Xu Dekang, Lin Hao, Yang Shenghong, Shao Yuanzhi, Zhang Yueli
State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials Science and Engineering/School of Physics, Sun Yat-sen University, Guangzhou, 510275, China.
Institute of Optoelectronic Engineering, Department of Optoelectronic Engineering, Jinan University, Guangzhou, 510632, China.
Sci Rep. 2016 Aug 10;6:31366. doi: 10.1038/srep31366.
Pure tetragonal phase, uniform and well-crystallized sodium gadolinium molybdate (NaGd(MoO4)2) nanocrystals with diverse morphologies, e.g. nanocylinders, nanocubes and square nanoplates have been selectively synthesized via oleic acid-mediated hydrothermal method. The phase, structure, morphology and composition of the as-synthesized products are studied. Contents of both sodium molybdate and oleic acid of the precursor solutions are found to affect the morphologies of the products significantly, and oleic acid plays a key role in the morphology-controlled synthesis of NaGd(MoO4)2 nanocrystals with diverse morphologies. Growth mechanism of NaGd(MoO4)2 nanocrystals is proposed based on time-dependent morphology evolution and X-ray diffraction analysis. Morphology-dependent down-shifting photoluminescence properties of NaGd(MoO4)2: Eu(3+) nanocrystals, and upconversion photoluminescence properties of NaGd(MoO4)2: Yb(3+)/Er(3+) and Yb(3+)/Tm(3+) nanoplates are investigated in detail. Charge transfer band in the down-shifting excitation spectra shows a slight blue-shift, and the luminescence intensities and lifetimes of Eu(3+) are decreased gradually with the morphology of the nanocrystals varying from nanocubes to thin square nanoplates. Upconversion energy transfer mechanisms of NaGd(MoO4)2: Yb(3+)/Er(3+), Yb(3+)/Tm(3+) nanoplates are proposed based on the energy level scheme and power dependence of upconversion emissions. Thermometric properties of NaGd(MoO4)2: Yb(3+)/Er(3+) nanoplates are investigated, and the maximum sensitivity is determined to be 0.01333 K(-1) at 285 K.
通过油酸介导的水热法选择性合成了纯四方相、均匀且结晶良好的钼酸钆钠（NaGd(MoO4)2）纳米晶体，其具有多种形貌，如纳米圆柱体、纳米立方体和方形纳米片。对合成产物的相、结构、形貌和组成进行了研究。发现前驱体溶液中钼酸钠和油酸的含量均对产物的形貌有显著影响，且油酸在形貌可控合成具有多种形貌的NaGd(MoO4)2纳米晶体中起关键作用。基于随时间变化的形貌演变和X射线衍射分析，提出了NaGd(MoO4)2纳米晶体的生长机制。详细研究了NaGd(MoO4)2:Eu(3+)纳米晶体的形貌依赖型下转换光致发光特性，以及NaGd(MoO4)2:Yb(3+)/Er(3+)和Yb(3+)/Tm(3+)纳米片的上转换光致发光特性。下转换激发光谱中的电荷转移带显示出轻微的蓝移，并且随着纳米晶体的形貌从纳米立方体变为薄方形纳米片，Eu(3+)的发光强度和寿命逐渐降低。基于上转换发射的能级图和功率依赖性，提出了NaGd(MoO4)2:Yb(3+)/Er(3+)、Yb(3+)/Tm(3+)纳米片的上转换能量转移机制。研究了NaGd(MoO4)2:Yb(3+)/Er(3+)纳米片的测温特性，确定在285K时的最大灵敏度为0.01333 K(-1)。
