Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Langmuir. 2012 Apr 3;28(13):5562-9. doi: 10.1021/la204981b. Epub 2012 Mar 20.
Amine-functionalized colloidal silica finds use in a variety of applications and fundamental investigations. To explore convenient methods of synthesis and characterization of research-grade materials in relatively large quantities, nearly monodisperse colloidal silica particles were prepared by base-catalyzed hydrolysis of reagent-grade tetraethyl orthosilicate (TEOS) without the traditional time- and energy-consuming distillation step. Radius was varied reliably from 30 to 125 nm by changing the water/TEOS ratio. Asymmetric flow field flow fractionation (AF4) methods with online light scattering detection proved effective in assessing the uniformity of the various preparations. Even highly uniform commercial standards were resolved by AF4. The surface of the colloidal silica was decorated with amino groups using (3-aminopropyl) trimethoxysilane and spacer methyl groups from methyl-trimethoxysilane. The surface density of amino groups was quantified spectrophotometrically after reaction with ninhydrin; the nature of this analysis avoids interference from sample turbidity. As an alternative to the ninhydrin test, an empirical relationship between surface density of amino groups and zeta potential at low pH was found. The size of the colloidal silica was predictably decreased by etching with HF; this method will be effective for some preparations, despite a modest reduction in size uniformity.
胺功能化胶体二氧化硅在各种应用和基础研究中都有使用。为了探索在相对大量的情况下合成和表征研究级材料的简便方法，我们使用碱催化水解试剂级四乙氧基硅烷（TEOS），而无需传统的耗时耗能蒸馏步骤，制备了近单分散胶体二氧化硅颗粒。通过改变水/TEOS 的比例，可靠地将粒径从 30nm 变化到 125nm。使用带有在线光散射检测的不对称流场流分离（AF4）方法有效地评估了各种制备物的均匀性。甚至高度均匀的商业标准也可以通过 AF4 得到解析。使用（3-氨丙基）三甲氧基硅烷和甲基三甲氧基硅烷中的间隔甲基基团，将胶体二氧化硅的表面修饰上氨基。反应后用茚三酮分光光度法定量氨基的表面密度；这种分析方法避免了样品浊度的干扰。作为茚三酮测试的替代方法，发现了在低 pH 值下表面密度的氨基与 ζ 电位之间的经验关系。使用 HF 进行蚀刻可预期地减小胶体二氧化硅的尺寸；尽管尺寸均匀性略有降低，但这种方法对某些制剂仍然有效。
