带电胶体粒子结晶过程的实验研究

Crystallization of charged colloidal particles:an experimental study

利用带电单分散聚苯乙烯胶体粒子,通过自组装机理,制备了体积百分比为4·8%的具有多晶结构的胶体晶体,并用Kossel衍射技术和紫外可见分光光度计分别对晶体的生长过程进行了监测.通过对Kossel的图像分析检测不同阶段相应的晶格结构,发现胶体结晶过程晶体结构演变顺序为由液态—随机层结构—堆无序结构—面心立方孪晶结构到面心立方结构.定量地确定了结晶过程中晶体不同晶面的晶面间距和晶体的晶格常数,通过紫外可见分光光度计测量的晶体透射谱图,计算得到111晶面的晶面间距和晶体的晶格常数,与用Kossel衍射技术得到的结果相一致,还发现随样品放置时间的延长,衰减峰变窄和加深,并向短波方向移动,对应着晶体的晶格常数减小的现象.

Colloidal crystals are fabricated through a self-assembly process of monodispersed polystyrene particles. Evolution of colloidal crystal structures is analyzed by Kossel diffraction technique and UV-Vis spectmphotometer. According to the changes in the Kossel patterns we find the crystal structures change with passage of time and experience successively the following stages： liquid state-random layer structure-stacking disorder structure-fcc with （111） twin-normal fcc structure. The plane distances of different crystal planes and the lattice constants are also determined in this study. The 111 plane distances and the lattice constants evaluated according to the measurement of transmission spectrum are in accordance with the results by the analysis of Kossel line. In addition, it was found that the peaks of the transmission spectrum become sharper and shift considerably toward shorter wavelength during the crystal evolution, showing the lattice constants become smaller.