Rapidly functionalized, water-dispersed carbon nanotubes at high concentration
Rapidly functionalized, water-dispersed carbon nanotubes at high concentration
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DOI：
10.1021/ja053003q
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发表时间：
2006-01-11
影响因子：
15
通讯作者：
Mitra, S
中科院分区：
文献类型：
--
作者：
Wang, YB;Iqbal, Z;Mitra, S
以硝酸和硫酸为介质，采用微波辅助功能化法对单壁碳纳米管进行功能化，制备了高水分散性的碳纳米管。在去离子水中获得了高达10 mg/mL的稳定浓度，比先前报道的高出近2个数量级。这是在仅3分钟的官能化反应之后。傅里叶变换红外光谱表明，存在的羧基（-COOH）和酸磺化（-SO2中心点OH或-SO 3- H+）的单壁碳纳米管的基团。在元素分析的基础上，估计三个碳原子中有一个被羧基化，而十个碳原子中有一个被磺化。在水性分散体和固相中拍摄的拉曼光谱表明电荷从SWNT骨架转移到官能团。从水悬浮液沉积的薄膜的扫描电子显微镜图像显示，单壁碳纳米管在基板上彼此平行排列。图像还表明纳米管的平均长度有所减少。从稀甲醇分散液的薄膜的透射电子显微镜图像显示，单壁碳纳米管被广泛地解开。激光散射粒度测量没有显示存在3-800 nm尺寸范围内的颗粒的证据，表明官能化的SWNT可能已经分散以形成真正的溶液。此外，微波处理的单壁碳纳米管被发现含有显着更少量的原始铁催化剂相对于存在于起始纳米管。发现从微波官能化的单壁碳纳米管获得的热退火薄膜的电导率与从起始纳米管的悬浮液获得的类似膜的电导率相同。
Microwave-assisted functionalization of single-wall carbon nanotubes (SWNTs) in a mixture of nitric and sulfuric acids was carried out to synthesize highly water-dispersible nanotubes. Stable concentrations as high as 10 mg/mL were obtained in deionized water that are nearly 2 orders of magnitude higher than those previously reported. This was after only 3 min of functionalization reaction. Fourier transform infrared spectra showed the presence of carboxylated (-COOH) and acid sulfonated (-SO2 center dot OH or -SO3- H+) groups on the SWNTs. On the basis of elemental analysis, it was estimated that one out of three carbon atoms was carboxylated, while one out of 10 carbon atoms was sulfonated. The Raman spectra taken both in aqueous dispersion and in the solid phase indicated charge transfer from the SWNT backbone to the functional groups. Scanning electron microscope images of thin films deposited from an aqueous suspension showed that the SWNTs were aligned parallel to one another on the substrate. The images also indicated some reduction in average length of the nanotubes. Transmission electron microscope images of thin films from a dilute methanol dispersion showed that the SWNTs were extensively debundled. Laser light scattering particle size measurements did not show evidence for the existence of particles in the 3-800 nm size range, indicating that the functionalized SWNTs might have dispersed to have formed a true solution. Moreover, the microwave-processed SWNTs were found to contain significantly smaller amounts of the original iron catalyst relative to that present in the starting nanotubes. The electrical conductivity of a thermally annealed thin membrane obtained from the microwave-functionalized SWNTs was found to be the same as that of a similar membrane obtained from a suspension of the starting nanotubes.