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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Pore size and surface charge control in mesoporous TiO_2 using post-grafted SAMs
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Pore size and surface charge control in mesoporous TiO_2 using post-grafted SAMs

机译：孔径和表面电荷控制在中孔TiO_2中使用接生后的Sams

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摘要

Two types of TiO_2 are used as mesoporous scaffolds, one (ⅰ) randomly sintered yielding an average pore size of 15-20 nm including bottlenecks of 1-3 nm (s-TiO_2), the other (ⅱ) prepared by evaporation-induced self-assembly with a pore size of 7-9 nm (t-TiO_2). The pore walls of these materials were post-grafted with phosphonic acids bearing one or two pyridinium or sulfonate head groups via 6, 10 or 14 methylene groups, in order to tune the free pore diameter and the surface charge over a broad range. The modification was characterized by FTIR spectroscopy. Charge transport through the modified pores was investigated by cyclic voltammetry using [Fe(CN)_6]~(4-/3-), [IrCl_6]~(2-/3-) [Ru(NH_3)_6]~(3+/2+), and (ferrocenylmethyl)trimethylammonium as electroactive tracer ions and La~(3+) or naphthalene trisulfonate as non-electroactive species. The Faradaic current through the pores is controlled by the combination of surface charge, tracer ion charge, charge of the non-electroactive ions present, as well as the pore diameter. High currents due to strong preconcentration are observed, e.g. a partitioning coefficient value of 7 x 10~3 for [Fe(CN)_6]~(4-/3-) on a modified electrode making it a candidate for ion-exchange voltammetry. Other phenomena presented are: (ⅰ) electrostatic closure of the porous system due to overlapping Debye layers, (ⅱ) charge inversion of the pore walls, and (ⅲ) the mode of charge propagation along the pore walls. Interestingly s-TiO_2 is more effective at building up an electrostatic barrier compared to t-TiO_2, probably because of narrow bottlenecks which interconnect the pores in s-TiO_2 only.
机译：两种类型的TiO_2用作中孔支架，一种（Ⅰ）随机烧结，产生15-20nm的平均孔径，包括1-3nm（S-TiO_2）的瓶颈，通过蒸发诱导的自身制备另一种（Ⅱ） - 孔径为7-9 nm（T-TiO_2）。这些材料的孔壁与含有一个或两个吡啶鎓或磺酸盐头部的膦酸通过6,10或14个亚甲基组接枝，以使自由孔径和表面电荷在宽范围内调谐。通过FTIR光谱表征改性。通过循环伏安法使用[Fe（CN）_6]〜（4- / 3-），[IRCL_6]〜（2- / 3-）[Ru（NH_3）_6]〜（3+ / 2 +），（二氧化环甲基）三甲基铵作为电活性示踪离子和La〜（3+）或萘三烷基磺酸盐作为非电活性物种。通过孔隙的游览电流通过表面电荷，示踪离子电荷，存在的非电活性离子的电荷以及孔径的组合来控制。例如，观察到由于强烈的前浓缩而导致的高电流。在修饰电极上的[Fe（CN）_6]〜（4- / 3-）的分隔系数值为7×10〜3，使其成为离子交换伏安法的候选物。所提出的其他现象是：（Ⅰ）多孔系统的静电闭合由于重叠的德语层，（Ⅱ）孔壁的电荷转化，和（Ⅲ）沿孔壁的电荷传播模式。与T-TiO_2相比，有趣的是，S-TiO_2在构建静电屏障时更有效，可能是因为狭窄的瓶颈仅在S-TiO_2中互连孔隙。

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