Enhanced electrostatic modulation of ionic diffusion through carbon nanotube membranes by diazonium grafting chemistry
Enhanced electrostatic modulation of ionic diffusion through carbon nanotube membranes by diazonium grafting chemistry
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DOI：
10.1016/j.memsci.2007.09.068
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发表时间：
2008-05-15
影响因子：
9.5
通讯作者：
Hinds, Bruce J.
中科院分区：
文献类型：
--
作者：
Majumder, Mainak;Keis, Karin;Hinds, Bruce J.
膜结构由横跨惰性聚合物基质的开口碳纳米管（内径类似于 7 nm）排列阵列组成，允许水性离子物质通过 CNT 核进行扩散传输。打开 CNT 尖端的等离子体氧化过程本质上在 CNT 尖端引入了羧酸基团，这使得 CNT 孔入口处具有有限数量的化学功能。然而，对于许多应用来说，重要的是增加孔入口处羧酸基团的密度，以实现有效的分离过程。水基重氮电化学显着增加了羧酸基团的功能密度。 pH 依赖性染料吸附-解吸和界面电容测量表明功能密度增加了 5-6 倍。为了进一步控制功能化学的空间位置，我们发现碳纳米管核心内的快速流动惰性液柱将重氮接枝仅限制在碳纳米管尖端。带有阴离子官能团的带正电荷的 Ru(bipy)(3)(+2) 通量增加证实了这一点。离子扩散的静电增强很容易在 0.1 M 电解质溶液中进行筛选，与膜孔几何形状和增加的功能密度一致。 (C) 2007 Elsevier B.V. 保留所有权利。
A membrane structure consisting of an aligned array of open ended carbon nanotubes (similar to 7 nm i.d.) spanning across an inert polymer matrix allows the diffusive transport of aqueous ionic species through CNT cores. The plasma oxidation process that opens CNTs tips inherently introduces carboxylic acid groups at the CNT tips, which allows for a limited amount of chemical functional at the CNT pore entrance. However for numerous applications, it is important to increase the density of carboxylic acid groups at the pore entrance for effective separation processes. Aqueous diazonium-based electrochemistry significantly increases the functional density of carboxylic acid groups. pH dependent dye adsorption-desorption and interfacial capacitance measurements indicate similar to 5-6 times increase in functional density. To further control the spatial location of the functional chemistry, a fast flowing inert liquid column inside the CNT core is found to restrict the diazonium grafting to the CNT tips only. This is confirmed by the increased flux of positively charged Ru(bipy)(3)(+2) with anionic functionality. The electrostatic enhancement of ion diffusion is readily screened in 0.1 M electrolyte solution consistent with the membrane pore geometry and increased functional density. (C) 2007 Elsevier B.V. All rights reserved.