合成条件对径向有序介孔二氧化硅中空亚微米球的形貌和结构的影响

Effects of Synthetic Conditions on the Morphology and Structure of Silica Hollow Submicrospheres with Radially Oriented Mesochannels

本文以硬模板与软模板结合的双模板方法(十六烷基三甲基溴化铵(CTAB)为介孔模板,聚苯乙烯(PS)球为中空模板),通过自组装制备出有良好分离性和单分散性且具有径向介孔的二氧化硅中空亚微米球.研究表明CTAB、TEOS的用量,催化剂的种类对二氧化硅中空亚微米球的形貌、壁厚、产品纯度等都有很大的影响.在保持其它实验条件不变的情况下,通过分别单独调节CTAB和TEOS的用量或同时调节CTAB和TEOS的用量,得出最佳原料配比是:TEOS/CTAB/NH3/乙醇/水的摩尔比是1∶0.27∶9.8∶304∶2955,TEOS/聚苯乙烯球的质量比是4/1.催化剂的种类对中空亚微米球的形貌也有较大影响,当NaOH(浓度为1 mol/L)的用量为0.05—0.10 mL时,生成由小粒子聚集而成的亚微米球;随着NaOH用量增大到0.10—0.20 mL,小粒子逐渐粘合在一起,亚微米球表面逐渐变光滑;进一步增大NaOH用量为0.20—0.30 mL则导致杂质小粒子的出现.在实验结果和文献报道的基础上,讨论并提出了径向有序介孔二氧化硅中空亚微米球的形成机理.

In this work,a dual-templating method using polystyrene submicrospheres（PS） as core template and cetyltrimethylammonium bromide（CTAB） as co-template（porogen） was developed to fabricate hollow silica submicrospheres with radially oriented mesochannels.The fabricated hollow submicrospheres were nearly monodisperse and well separated.The amounts of CTAB and tetraethoxysilane（TEOS） and the kinds of catalyst were shown to have large effects on the morphology,shell thickness and purity of the fabricated hollow submicrospheres.When the amount of CTAB was 0.077 g,severe coalescence of hollow submicrospheres occurred.When the amount of CTAB increased to 0.110 g,the obtained hollow submicrospheres were well dispersed.When the amount of CTAB further increased to 0.143 g,however,impurity of silica nanoparticles increased.When the amount of TEOS was 0.175 mL,the morphology of hollow submicrospheres was less spherical and the shell thickness was not uniform.When the amount of TEOS was 0.250 mL,hollow submicrospheres of good integrity and uniform shell thickness were obtained.When the amount of TEOS further increased to 0.325 mL,the shell thickness of hollow submicrospheres increased significantly and a small amount of silica nanoparticles appeared simultaneously as impurity.The morphology of hollow submicrospheres was also largely affected by the kinds of catalyst.When the amount of NaOH（concentration： 1 mol/L） was 0.05-0.10 mL,spherical aggregates of small silica nanoparticles formed.With increase of the NaOH amount to 0.10-0.20 mL,the small silica nanoparticles gradually fused together and the surface of spherical aggregate became smooth.When the NaOH amount further increased to 0.20-0.30 mL,smaller silica nanoparticles appeared simultaneously as impurity.On the basis of our experimental results and other reports,a tentative mechanism was proposed for the formation of silica hollow submicrospheres with radially oriented mesochannels.