Shape Transformation and Surface Melting of Cubic and Tetrahedral Platinum Nanocrystals
Shape Transformation and Surface Melting of Cubic and Tetrahedral Platinum Nanocrystals
复制标题
DOI：
10.1021/jp981594j
复制
发表时间：
1998-07
影响因子：
3.3
通讯作者：
Zhong Lin Wang;J. Petroski;A. T. Green;M. El-Sayed
中科院分区：
文献类型：
--
作者：
Zhong Lin Wang;J. Petroski;A. T. Green;M. El-Sayed
我们报道了原位温度诱导的聚合物覆盖的立方和四面体纳米晶体的形状转变和熔化行为的透射电镜研究。我们的研究结果表明，通过在180至250°C之间的温度下退火样品，表面覆盖聚合物被去除。在~ 350°C温度下，颗粒形状没有变化。在350 ~ 450℃的温度范围内，颗粒形状发生了小的截断，但没有观察到大的形状转变。当温度升高到~ 500°C以上时，颗粒形状经历了戏剧性的转变，变成球形形状，在那里发生表面扩散或表面预熔（软化）。在600°C以上，表面熔化变得明显，导致相邻纳米晶体表面聚并，组装纳米晶体的体积减小。表面熔化在纳米晶体的固体核心周围形成了几个原子层深的液体层。这个温度…
We report transmission electron microscopic studies of in-situ temperature-induced shape transformation and melting behavior of polymer-capped cubic and tetrahedral nanocrystals. Our results indicate that the surface-capping polymer is removed by annealing the specimen at temperatures between 180 and 250 °C. The particle shapes show no change up to ∼350 °C. In the temperature range between 350 and 450 °C, a small truncation occurs in the particle shapes but no major shape transformation is observed. The particle shapes experience a dramatic transformation into spherical-like shapes when the temperature is raised above ∼500 °C, where surface diffusion or surface premelting (softening) takes place. Above 600 °C, surface melting becomes obvious leading to coalescence of the surfaces of neighboring nanocrystals and a decrease in the volume occupied by the assembled nanocrystals. The surface melting forms a liquid layer a few atomic layers deep around the still solid core of the nanocrystal. This temperature i...