Counterion effect in acid synthesis of mesoporous silica materials
Counterion effect in acid synthesis of mesoporous silica materials
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DOI：
10.1021/jp000010m
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发表时间：
2000-07
影响因子：
3.3
通讯作者：
Hong‐Ping Lin;Chia-Pei Kao;C. Mou;Shang-Bin Liu
中科院分区：
文献类型：
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作者：
Hong‐Ping Lin;Chia-Pei Kao;C. Mou;Shang-Bin Liu
采用不同的酸源HX，在酸性条件下合成了具有有序六方结构的介孔硅材料。在相同的酸浓度下，HNO3 < HBr < HCl < H2SO4溶致系列中，细观结构降水形成的诱导时间增加。用胶束催化反应方案分析了诱导速率。诱导时间的顺序反映了X -的反离子结合强度。反离子结合强度最高的硝酸往往形成很长的胶束。测定了反离子缔合常数，并在合成条件下测定了溶液中反离子的解离度。在早期形态形成阶段，这种联系只是部分的。HNO3是制备层次化二氧化硅绳的合适酸源，二氧化硅绳是由平行纳米通道组成的二氧化硅纤维。表面活性剂胶束的伸长率和剪切流动是形貌的控制因素。温度、酸浓度、表面活性剂链长和极性溶剂的加入对酸性条件下介孔材料的形貌和纳米结构也有很强的影响。
Mesoporous silica materials with well-ordered hexagonal structure were synthesized under acidic conditions by using various acid sources HX. The induction time for the formation of mesostructural precipitation increases in the lyotropic series HNO3 < HBr < HCl < H2SO4 under the same acid concentration. The induction rates are analyzed with a micelle-catalyzed reaction scheme. The order in induction time reflects the strength in counterion binding of X - . Nitric acid with the highest binding strength of counterion tends to form very long micelles. We have determined the counterion association constants and found the degree of counterion dissociation under synthetic conditions in solution. The association is only partial during the early morphologysetting stage. HNO3 is a suitable acid source for preparing silica ropes of hierarchical order, consisting of silica fibers formed from parallel nanosized channels. The elongation of the surfactant micelles and shearing flow are the controlling factors in the morphology. Temperature, acid concentration, surfactant chain length, and the addition of polar solvent also have strong influence on the morphology and nanostructure of the mesoporous materials under acidic conditions.