State Key Lab of Structural Chemistry, Fujian Institute of Research on the Structure of Matter and Graduate School of the Chinese Academy of Sciences, Fuzhou 350002, People's Republic of China.
Phys Chem Chem Phys. 2012 Jul 28;14(28):9956-65. doi: 10.1039/c2cp41136a. Epub 2012 Jun 19.
This work explores the size-induced lattice modification and its relevance to photoluminescence properties of tetragonal zircon-type GdVO(4):Eu(3+) nanostructures. GdVO(4):Eu(3+) nanoparticles with crystallite sizes ranging from 14.4 to 24.7 nm were synthesized by a hydrothermal method using sodium citrate as a capping agent. Regardless of the reaction temperatures, all samples retained an ellipsoidal-like morphology. Nevertheless, as the crystallite size reduces, there appears a tensile strain and lattice distortion, which is accompanied by a lattice expansion and a decreased symmetry of structural units. These lattice modifications could be associated with the changes in the interior chemical bonding due to the interactions of surface defect dipoles that have imposed an increased negative pressure with crystallite size reduction. Furthermore, crystallite size reduction also led to a significant increase in the amounts of surface hydroxyl groups and citric species, as well as the concentration of the surface Eu(3+) ions. When Eu(3+) was taken as a structural probe, it was found that the asymmetric ratio (I(02)/I(01)) of Eu(3+) gradually declined to show a remarkable decrease in color chromaticity as crystallite size reduces, which could be interpreted as due to the change of local environments of Eu(3+) ions from the interior to the surface of the nanoparticles.
这项工作探讨了尺寸诱导的晶格修饰及其与四方锆石型 GdVO(4):Eu(3+) 纳米结构光致发光性能的关系。使用柠檬酸钠作为封端剂，通过水热法合成了晶粒尺寸在 14.4 至 24.7nm 之间的 GdVO(4):Eu(3+) 纳米粒子。无论反应温度如何，所有样品都保持类似椭圆形的形态。然而，随着晶粒尺寸的减小，会出现拉伸应变和晶格畸变，这伴随着晶格膨胀和结构单元对称性的降低。这些晶格修饰可能与由于表面缺陷偶极子的相互作用导致的内部化学结合的变化有关，这种相互作用在晶粒尺寸减小时施加了更大的负压。此外，晶粒尺寸的减小还导致表面羟基和柠檬酸基团的数量以及表面 Eu(3+) 离子的浓度显著增加。当以 Eu(3+)作为结构探针时，发现 Eu(3+)的不对称比 (I(02)/I(01))逐渐降低，表明随着晶粒尺寸的减小，颜色色度明显降低，这可以解释为由于 Eu(3+)离子的局部环境从纳米粒子的内部到表面发生了变化。
