Silicon dioxide (SiO₂) obtained by Sol–Gel methods is widely used as adsorbents, catalytic supports, filter membranes and in drugs delivery, among others. For most of the applications, surface area and porosity are key parameters that should be controlled, depending on the purpose of the material. These characteristics depend on the chemistry of the precursors in solution. Silicon alkoxides are commonly used as precursors, where the chemical pathway to produce sols and then gels depends on several factors such as water/alcohol ratio, pH, type of catalyst, temperature, etc. In order to control the microstructural characteristics of SiO₂, it is necessary to understand the effect of the different chemical components on the hydrolysis-condensation reactions. In this work, we explored the acid-catalyzed hydrolysis and condensation reactions of silicon tetra-ethyl-alkoxide (TEOS) employing three common acids: HF, HCl, and HNO₃. Gel formation kinetics was studied by low field nuclear magnetic resonance. Structural evolution of gels and xerogels at the nanoscale was determined by small angle X-ray scattering (SAXS). The microstructure of xerogels was determined by nitrogen adsorption (BET method), and by scanning and transmission electron microscopy (SEM and TEM, respectively). The final SiO₂ products revealed different porosity type and texture depending on the acid employed, which are related to the chemical pathway during the sol–gel transition.

通过溶胶-凝胶法获得的二氧化硅 (SiO ₂ ) 被广泛用作吸附剂、催化载体、过滤膜和药物输送等。对于大多数应用，表面积和孔隙率是应该控制的关键参数，具体取决于材料的用途。这些特性取决于溶液中前体的化学性质。硅醇盐通常用作前体，其中产生溶胶然后凝胶的化学途径取决于几个因素，例如水/醇比、pH、催化剂类型、温度等。为了控制 SiO ₂的微观结构特征，有必要了解不同化学成分对水解缩合反应的影响。在这项工作中，我们探索了使用三种常见酸：HF、HCl 和 HNO _{3 的}四乙基烷氧基硅 (TEOS) 的酸催化水解和缩合反应。通过低场核磁共振研究凝胶形成动力学。通过小角 X 射线散射 (SAXS) 确定纳米级凝胶和干凝胶的结构演变。干凝胶的微观结构通过氮吸附（BET 方法）、扫描和透射电子显微镜（分别为 SEM 和 TEM）测定。最终的 SiO ₂ 根据所使用的酸，产品显示出不同的孔隙率类型和质地，这与溶胶-凝胶转变过程中的化学途径有关。