Fujimoto Kota, Ishikawa Shunho, Watanabe Kanako, Ishii Haruyuki, Suga Keishi, Nagao Daisuke
Department of Chemical Engineering, Tohoku University, 6-6-07 Aoba, Aramaki-aza, Aoba-ku, Sendai, Miyagi 980-8579, Japan.
Department of Sustainable Environmental Engineering, Yamaguchi University, 2-16-1, Tokiwadai, Ube, Yamaguchi 755-0097, Japan.
ACS Omega. 2021 Jun 30;6(27):17734-17740. doi: 10.1021/acsomega.1c02293. eCollection 2021 Jul 13.
Mesoporous silica shells were formed on nonporous spherical silica cores during the sol-gel reaction to elucidate the mechanism for the generation of secondary particles that disturb the efficient growth of mesoporous shells on the cores. Sodium bromide (NaBr) was used as a typical electrolyte for the sol-gel reaction to increase the ionic strength of the reactant solution, which effectively suppressed the generation of secondary particles during the reaction wherein a uniform mesoporous shell was formed on the spherical core. The number of secondary particles ( ) generated at an ethanol/water weight ratio of 0.53 was plotted against the Debye-Hückel parameter κ to quantitatively understand the Debye screening effect on secondary particle generation. Parameter κ, where is the average radius of the secondary particles finally obtained in the silica coating, expresses the trend in at different concentrations of ammonia and NaBr. was much lower than that expected theoretically from the variation of secondary particle sizes at a constant Debye-Hückel parameter. A similar correlation with κ was observed at the high and low ethanol/water weight ratios of 0.63 and 0.53, respectively, with different hydrolysis rate constants. The good correlation between and κ revealed that controlling the ionic strength of the silica coating is an effective approach to suppress the generation of secondary particles for designing mesoporous shells with thicknesses appropriate for their application as high-performance liquid chromatography column packing materials.
在溶胶 - 凝胶反应过程中，在无孔球形二氧化硅核上形成了介孔二氧化硅壳层，以阐明干扰核上介孔壳层高效生长的二次颗粒的生成机制。溴化钠（NaBr）用作溶胶 - 凝胶反应的典型电解质，以提高反应物溶液的离子强度，这有效地抑制了反应过程中二次颗粒的生成，在此反应中，球形核上形成了均匀的介孔壳层。将乙醇/水重量比为0.53时产生的二次颗粒数量（ ）与德拜 - 休克尔参数κ作图，以定量了解德拜屏蔽效应对二次颗粒生成的影响。参数κ，其中 是最终在二氧化硅涂层中获得的二次颗粒的平均半径，表示在不同氨和NaBr浓度下 的趋势。 远低于在恒定德拜 - 休克尔参数下二次颗粒尺寸变化理论预期的值。在乙醇/水重量比分别为0.63和0.53的高、低比例下，观察到与κ有类似的相关性，且水解速率常数不同。 与κ之间的良好相关性表明，控制二氧化硅涂层的离子强度是抑制二次颗粒生成的有效方法，可用于设计厚度适合作为高效液相色谱柱填料应用的介孔壳层。
