在单粒子尺度下用胶体研究相变

Phase transition studies at the single-particle level using colloidal systems

悬浮于溶液中的微米胶体粒子可以自组装成多种结构,与原子一样具有丰富的相行为,通过调节粒子的大小、形状、相互作用或密度可以驱动相变。由于胶体粒子可以在光学显微镜下直接成像并测量其热运动轨迹,因此是研究相变微观过程的一种有力的模型系统。近十几年来,作用力可调粒子、非球形粒子和活性粒子的制备有了突破性进展,并在自组装技术和相应的计算机模拟中有很大进步,因此为相变研究开辟了许多可能性。文章总结了利用胶体研究相变过程的最新进展,重点关注结晶、熔化和固—固相变,并简述胶体相变研究中存在的挑战和未来前景。

Micrometer-sized colloidal particles in suspension can self-assemble into various structures and exhibit rich phase behaviors as atoms. Phase transitions can be driven by tuning the particles＇ size, shape, interaction or number density. In particular, colloidal particles can be directly imaged and their thermal-motion trajectories can be tracked under optical video microscopy, which provides powerful model systems to study the microscopic kinetics of phase transitions. Many possible studies on phase transition are opened, due to the great advances in synthesizing colloids with tunable interaction, nonspherical shape and activity, and in self-assembly and computer simulation techniques in recent years. Here, we summarize the recent studies on phase transitions in colloidal model systems, with an emphasis on crystallization, melting and solid-solid transition. We also briefly point out the challenges and future directions in this field.