Visualization of the impurity diffusion by using charged colloidal crystals as models

原位观察杂质在原子/分子晶格中的扩散是相当困难的。因此，胶体晶体作为研究这种扩散行为的模型引起了人们极大的关注。胶体晶体作为研究结晶的模型具有多种优势。也就是说，(1)光学显微镜可以很容易地观察到单个粒子，(2)有各种控制粒子间相互作用的实验参数，(3)特征时间足够长，可以观察到非平衡和动态过程。在这里，我们报道了用光学显微镜直接观察胶体晶体中的杂质颗粒。我们可以确定粒子的轨迹，它显示了两个格点之间的跳跃行为。这是扩散的基本步骤。

In-situ observation of impurities diffusion in atomic/molecular crystal lattices is quite difficult. Therefore colloidal crystals have attracted considerable attention as models to study such diffusion behavior. Colloidal crystals have various advantages to study the crystallization as models. That is, (1) the individual particles can be easily observed by optical microscopy, (2) there are various experimental parameters which control the interparticle interaction, and (3) the characteristic time is long enough to observe non-equilibrium and dynamic processes. Here, we report the direct observation of the impurity particles of the colloidal crystals by optical microscopy. We could determine the trajectory of the particles, which shows hopping behavior between two lattice points. It is the elementary step of the diffusion.