State Key Lab of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, People's Republic of China.
Nanotechnology. 2013 Aug 2;24(30):305701. doi: 10.1088/0957-4484/24/30/305701. Epub 2013 Jun 27.
Metal oxide nanomaterials have been found to have great potential for diverse applications due to their unique relationships between structure and properties. Lattice expansion as particle size reduces was previously considered to be general for metal oxide nanomaterials. It is now a great challenge to see if lattice contraction could be induced by the size effect for metal oxide nanomaterials. ABO4 metal oxides (e.g., CaWO4, GdVO4, and CdWO4) are some of the most important functional materials with many applications, while such oxides at the nanoscale are never reported to show a lattice contraction. This work presents a first report on the variation from lattice expansion to lattice contraction by tuning the microstructures of GdVO4:Eu(3+) nanocrystals. A hydrothermal method was adopted to synthesize GdVO4:Eu(3+) nanocrystals, and then these nanoparticles were calcined at 600 ° C in air. It is found that particle size reduction led to a lattice contraction for the calcined samples, which is in contrast to the lattice expansion observed for the hydrothermally synthesized counterparts or many other metal oxide nanomaterials. In addition, the lattice symmetry of the calcined samples remained almost a constant. The results indicate that the negative surface stress was eliminated by calcination treatment, leading to a homogeneous compression process in the lattice structure of the calcined GdVO4:Eu(3+) nanocrystals. Furthermore, Eu(3+) was taken as a structural probe and a luminescence center to study the local environments pertinent to these structural changes and to optimize the photoluminescence performance.
金属氧化物纳米材料由于其结构与性能之间的独特关系，在多种应用中具有巨大的潜力。以前认为，随着粒径的减小，晶格膨胀是金属氧化物纳米材料的普遍现象。现在的一个巨大挑战是，看看晶格收缩是否可以通过尺寸效应来诱导金属氧化物纳米材料。ABO4 金属氧化物（例如 CaWO4、GdVO4 和 CdWO4）是最重要的功能材料之一，具有许多应用，而在纳米尺度上从未报道过这些氧化物会出现晶格收缩。本工作首次报道了通过调谐 GdVO4:Eu(3+)纳米晶的微结构，从晶格膨胀到晶格收缩的变化。采用水热法合成 GdVO4:Eu(3+)纳米晶，然后将这些纳米颗粒在空气中于 600°C 下煅烧。结果发现，粒径减小导致煅烧样品的晶格收缩，这与水热合成的对应物或许多其他金属氧化物纳米材料观察到的晶格膨胀相反。此外，煅烧样品的晶格对称性几乎保持不变。结果表明，煅烧处理消除了负表面应力，导致煅烧 GdVO4:Eu(3+)纳米晶晶格结构的均匀压缩过程。此外，Eu(3+)被用作结构探针和发光中心，以研究与这些结构变化相关的局部环境，并优化光致发光性能。
