Influence of Surface Oxides on the Colloidal Stability of Multi-Walled Carbon Nanotubes: A Structure-Property Relationship
Influence of Surface Oxides on the Colloidal Stability of Multi-Walled Carbon Nanotubes: A Structure-Property Relationship
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DOI：
10.1021/la901128k
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发表时间：
2009-09-01
期刊：
影响因子：
3.9
通讯作者：
Fairbrother, D. Howard
中科院分区：
文献类型：
--
作者：
Smith, Billy;Wepasnick, Kevin;Fairbrother, D. Howard
与所有纳米材料一样，碳纳米管 (CNT) 中的大部分原子位于表面或表面附近。因此，表面化学泔水在决定碳纳米管在水生环境中的命运和运输方面发挥着至关重要的作用。通常，含氧官能团（表面氧化物）被有意接枝到 CNT 表面以促进胶体稳定性。研究氧浓度和氧官能团分布对多壁碳纳米管（MWCNTs）胶体稳定性的影响。使用不同的氧化剂和反应条件创建了一套氧化多壁碳纳米管（O-MWCNT）。通过对 Milli-Q 水中的 O-MWCNT 粉末进行低功率超声处理，制备稳定的胶体悬浮液。 TEM、A FM、DLS 和 XPS 测量结果表明，无论表面化学性质如何，。胶体悬浮液由具有相当长度分布的单个纳米管组成。使用 NaCl 作为电解质，通过时间分辨动态光散射 (TR-DLS) 测量表现出不同表面化学性质的 O-MWCNT 的临界凝固浓度 (CCC)。在一系列与环境相关的 pH 值范围内，我们发现 CCC、总氧浓度和 O-MWCNT 的表面电荷之间存在线性相关性。与表面电荷相反，电泳迁移率并未被证明是衡量胶体稳定性的有用指标。从化学衍生化研究中获得的信息。与XPS结合进行的研究表明，含氧官能团的分布也会影响O-MWCNT的胶体稳定性，其中羧酸基团起着最重要的作用。这项研究强调了这样一个事实：可以开发定量关系来合理化表面化学对水生环境中纳米材料行为的影响。
As with all nanomaterials, a large fraction of the atoms in carbon nanotubes (CNTs) reside at or near the surface. Consequently, surface chemistry swill play a crucial role in determining the fate and transport of CNTs in aquatic environments. Frequently, oxygen-containing functional groups (surface oxides) are deliberately grafted into the CNT surface to promote colloidal stability. To study the influence that both the oxygen concentration and the oxygen functional-group distribution have on the colloidal stability of multiwalled carbon nanotubes (MWCNTs). a suite of oxidized MWCNTs (O-MWCNTs) were created using different oxidizing agents and reaction conditions. Stable colloidal suspensions were prepared by low-power sonication of O-MWCNT powders in Milli-Q water. Results from TEM, A FM, DLS, and XPS measurements revealed that, irrespective of the surface chemistry, the. colloidal suspensions were composed of individual nanotubes with comparable length distributions. The critical coagulation concentrations (CCC) of O-MWCNTs that exhibited different surface chemistries were measured with time-resolved dynamic light scattering (TR-DLS) using NaCl as the electrolyte. Over a range of environmentally relevant pH values, linear correlations were found to exist between the CCC, total oxygen concentration, and surface charge of O-MWCNTs. In contrast to surface charge, electrophoretic mobility did not prove to be a useful metric of colloidal stability. Information obtained from chemical derivatization studies. carried out in conjunction with XPS, revealed that the distribution of oxygen-containing functional groups also influences the colloidal stability of O-MWCNTs, with carboxylic acid groups playing the most important role. This study highlights the fact that quantitative relationships can be developed to rationalize the influence of surface chemistry on the behavior of nanomaterials in aquatic environments.