Purification of Single Wall Carbon Nanotubes

选用聚醚砜制成的0.3微米孔径的膜过滤器，用于将单壁碳纳米管(SWNTs)与含有单壁碳纳米管(SWNTs)的弧形或激光蒸发碳烟分离。在微滤前，使用常规的超声波振荡浴将烟尘分散在0.1%的阳离子表面活性剂(苯扎氯铵)的水溶液中。如果起始烟尘中含有大量的无定形碳纳米球和其他纳米粒子，则需要进行前处理以增加烟尘中的单壁碳纳米管含量。因为，纳米球很容易粘在膜过滤器的表面/或孔内。离心分离的样品溶液与微滤的样品溶液相同。对于多壁碳纳米管(MWNTs)和单壁碳纳米管(…)，选择转子半径为8 cm的离心机的转速分别为5000rpm和12000-15000 rpm，以分离小管和碳纳米管更多的纳米球。通过这种离心法，MWNTs和SWNTs的含量可以分别从几十个(MWNTs)到几个(SWNTs)%的管状含量分别增加到超过85%和40%以上(Fe/Ni或Co/Ni双金属催化剂)。在增加了单壁碳纳米管的微管含量后，采用微滤分离，成功地将单壁碳纳米管的微管含量提高到了70-80%。进一步的提纯是在420-450ﾟC的干燥空气中燃烧20-40分钟。然后在浓盐酸溶液中浸泡，以去除无定形碳和金属残留物。在这里，重要的是在干燥的空气中进行燃烧，因为空气中的水分在低得多的温度下很容易攻击管子的碳网。最终得到的单壁碳纳米管纯度在90%以上。目前，每一种提纯过程中，大约有10到30毫克的提纯单壁碳纳米管可用于制备。电子自旋共振、拉曼散射和碱金属掺杂的研究正在进行中。将安排一项研究单壁碳纳米管束中氢吸附的研究计划。较少

0.3 mum pore sized membrane filter made by poly-ether sulfone was selected for a filter separating the single wall carbon nanotubes (SWNTs) from the arc or laser vaporized carbon soot containing SWNTs. In prior to the microfiltration, the soot was dispersed in an aqueous solution of 0.1% cationic surfactant (benzalkonium chloride) using a conventional ultrasonic vibration bath.If a starting soot contains numerous number of amorphous carbon nanospheres and other nanoparticles, it was necessary to carry out a pre-treatment to increase the SWNT content in the soot using a centrifugal separation. Because, the nanospheres easily stick on the surface /or in the pore of the membrane filter. The sample solution for the centrifugal separation is the same as that for the microfiltration. The spinning speeds of centrifuge with a 8 cm of rotor radius were selected at 5000 rpm and 12000-15000 rpm, respectively, for multiwall carbon nanotubes (MWNTs) and SWNTs to separate the tubules and the carbon … More nanospheres. By this centrifugal process, the contents of MWNTs and SWNTs could be increased, respectively, to in excess of 85 % and 40 % from a few tens (MWNTs) to a few (SWNTs) % of tubule content in the arc derived as-prepared soot (from an Fe/Ni or Co/Ni bimetallic catalyst). After increasing the tubule content, we applied the mictofiltration separation and succeed to increase the tubule content up to 70-80 %.Futher purification for SWNTs was carried out by using a combustion at 420-450ﾟC in dry air for 20-40 min. followed by a soaking in concentrated HCl solution to remove amorphous carbons and metal residua. Here, it is important to carry out the combustion in dry air, since the moisture in air easily attack the carbon network of the tubule at much lower temperature. Purity of the final SWNT product was in excess of 90 %. About 10 to 30 mg of purified SWNTs are now available to prepare per one purification procedure stated above.The electron spin resonance, Raman scattering and alkaline metal doping studies are now progressing. A researching plan for the study of hydrogen adsorption into the SWNT bundles will be scheduled. Less