Formation Mechanism for Hexagonal-Structured Self-Assemblies of Nanocrystalline Titania Templated by Cetyltrimethylammonium Bromide
Formation Mechanism for Hexagonal-Structured Self-Assemblies of Nanocrystalline Titania Templated by Cetyltrimethylammonium Bromide
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DOI：
10.5650/jos.57.629
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发表时间：
2008-11-01
影响因子：
1.5
通讯作者：
Abe, Masahiko
中科院分区：
文献类型：
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作者：
Sakai, Toshio;Yano, Hanae;Abe, Masahiko
以十六烷基三甲基溴化铵（C16 H33 N（CH 3）（3）Br; CTAB）为模板，在不添加任何其他添加剂的条件下，将含有十六烷基三甲基溴化铵（C16 H33 N（CH 3）（3）Br; CTAB）球形胶束的水溶液与作为二氧化钛前驱体的水合硫酸氧钛（TiOSO 4中心点xH（2）SO（4）中心点xH（2）O）混合，形成了具有阻碍结构的纳米二氧化钛自组装体（Hex-ncTiO（2）/CTAB纳米骨架）。从反应温度、二氧化钛前驱体/十六烷基三甲基溴化铵（CTAB）配比、表面活性剂种类、静电相互作用、胶束形成和分子组成等方面探讨了Hex-ncTiO（2）/CTAB纳米骨架的形成机理。我们发现，在较高的温度和较低的二氧化钛前体含量的水溶液中，晶体（结晶）二氧化钛（多晶型结晶）的晶体生长得到促进。此外，我们还发现，在聚阳离子、聚烯丙基胺盐酸盐（[CH_2CH（CH_2NH_2）HCl]（n）; PAH）和甲酰胺（HCONH_2）溶液中形成了结晶（α）二氧化钛。另一方面，在阴离子体系如十二烷基硫酸钠（CH 3（CH 2）（n）OSO 3 Na; SDS）和聚（4-苯乙烯磺酸钠）（[C8 H7 SO 3 Na]（n）; PSSS）中没有观察到二氧化钛形成。这表明二氧化钛前体的水解反应不仅由分子和聚合物中的阳离子引发，而且由氮原子引发。只有阳离子表面活性剂胶束溶液中才能形成受阻结构，而聚阳离子溶液和甲酰胺溶液中不形成受阻结构。
Hexagonal-structured self-assemblies of nanocrystalline (anatase) titania templated by cetyltrimethylammonium bromide (C16H33N(CH3)(3)Br; CTAB) (Hex-ncTiO(2)/CTAB Nanoskeleton) were formed after mixing of aqueous solutions containing CTAB spherical micelles and titanium oxysulfate acid hydrate (TiOSO4 center dot xH(2)SO(4)center dot xH(2)O) as a titania precursor in the absence of any other additives. Formation mechanism of the Hex-ncTiO(2)/CTAB Nanoskeleton was examined in terms of the reaction temperature, titania precursor/CTAB mixing ratio, surfactant type, electrostatic interaction, micelle formation and molecular component. We found that crystal growth of crystalline (anatase) titania (polymorphic crystallization) was promoted with higher temperature and lower titania precursor content in aqueous solutions. In addition, we revealed that the crystalline (anatase) titania was formed in polycation, poly(allylamine hydrochloride ([CH2CH(CH2NH2)HCl](n); PAH), and formamide (HCONH2) solutions. On the other hand, no titania formation was observed in anionic systems such as sodium dodecyl sulfate (CH3(CH2)(n)OSO3Na; SDS) and poly(sodium 4-styrenesulfonate ([C8H7SO3Na](n); PSSS). This indicates that hydrolysis reaction of the titania precursor is initiated by not only cations but also nitrogen atoms in molecules and polymers. Hexagonally structure was formed in only cationic surfactant micellar solutions but not in polycation solutions and formamide.