Adsorption, Desorption, Surface Diffusion, Lattice Defect Formation, and Kink Incorporation Processes of Particles on Growth Interfaces of Colloidal Crystals with Attractive Interactions

Good model systems are required in order to understand crystal growth processes because, in many cases, precise incorporation processes of atoms or molecules cannot be visualized easily at the atomic or molecular level. Using a transmission-type optical microscope, we have successfully observed in situ adsorption, desorption, surface diffusion, lattice defect formation, and kink incorporation of particles on growth interfaces of colloidal crystals of polystyrene particles in aqueous sodium polyacrylate solutions. Precise surface transportation and kink incorporation processes of the particles into the colloidal crystals with attractive interactions were observed in situ at the particle level. In particular, contrary to the conventional expectations, the diffusion of particles along steps around a two-dimensional island of the growth interface was not the main route for kink incorporation. This is probably due to the number of bonds between adsorbed particles and particles in a crystal; the number exceeds the limit at which a particle easily exchanges its position to the adjacent one along the step. We also found novel desorption processes of particles from steps to terraces, attributing them to the assistance of attractive forces from additionally adsorbing particles to the particles on the steps

Bound Pairs: Direct Evidence for Long-range Attraction between Like-Charged Colloids

We report observations of stable bound pairs in very dilute deionized aqueous suspensions of highly charged polystyrene colloidal particles, with monovalent counterions, using a confocal laser scanning microscope. Through an analysis of several thousands of time series of confocal images recorded deep inside the bulk suspension, we find that the measured pair-potential, U(r) has a long-range attractive component with well depths larger than the thermal energy. These observations provide a direct and unequivocal evidence for the existence of long-range attraction in U(r) of like-charged colloidal particles.Comment: 8 pages, 4 figures, submitted to Phys. Rev. Let

Thermally Induced Unidirectional Crystallization of Charged Colloids(Poster session 1, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

この論文は国立情報学研究所の電子図書館事業により電子化されました。荷電コロイド粒子分散液は、粒子間の静電相互作用が十分大きいとき、粒子が規則配列した"結晶"構造を形成する。本研究では、昇温により粒子表面電荷数が増加して結晶化するコロイド系(ピリジン共存シリカ粒子/水分散液;粒径～100nm;粒子体積分率=0.035)を用い、加熱により結晶を一方向成長させた。大型(1mm×1cm×3cm)かつ試料セル壁面に良好に配列した、単一ドメイン結晶が生成した。結晶化機構および成長曲線について、試料温度分布の測定結果に基づいて議論する