Murai Masako, Yamada Hiroshi, Yamanaka Junpei, Onda Sachiko, Yonese Masakatsu, Ito Kensaku, Sawada Tsutomu, Uchida Fumio, Ohki Yoshimasa
Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603, Japan.
Langmuir. 2007 Jul 3;23(14):7510-7. doi: 10.1021/la700754s. Epub 2007 May 27.
Dilute aqueous dispersions of charged colloidal silica (particle volume fraction = approximately 0.03-0.04, particle diameter = 110 nm) exhibit unidirectional crystal growth due to the diffusion of a weak base, pyridine (Py). Similar diffusion-crystallization is enabled by a salt of a weak acid and a strong base, sodium hydrogen carbonate (NaHCO3). The resulting crystals consist of columnar (or cubic) crystal grains with a maximum height of a few centimeters and a maximum width of 1 cm. The crystal growth process is attributed to a combination of (i) the diffusion of Py or NaHCO3 accompanied by a charging reaction of the silica particles and (ii) the charge-induced crystallization of the silica colloids. Theoretical growth curves based on the reaction-diffusion model for the case of Py were in good agreement with the observed curves. We also report the immobilization of the resulting large crystals by using a polymer hydrogel matrix.
带电胶体二氧化硅的稀水分散体（颗粒体积分数约为0.03 - 0.04，颗粒直径为110 nm）由于弱碱吡啶（Py）的扩散而呈现单向晶体生长。弱酸强碱盐碳酸氢钠（NaHCO₃）也能实现类似的扩散结晶。所得晶体由柱状（或立方）晶粒组成，最大高度为几厘米，最大宽度为1厘米。晶体生长过程归因于：（i）Py或NaHCO₃的扩散以及二氧化硅颗粒的充电反应；（ii）二氧化硅胶体的电荷诱导结晶。基于Py情况的反应扩散模型的理论生长曲线与观察到的曲线吻合良好。我们还报告了使用聚合物水凝胶基质固定所得大晶体的情况。
