聚乙烯醇修饰的碳纳米管在缓冲溶液中的溶解过程

采用水溶性的聚乙烯醇修饰多壁碳纳米管表面,研究了聚乙烯醇修饰的碳纳米管在水浴摇床Tris-HCl缓冲溶液中的溶解过程.通过红外光谱,差示扫描量热仪,透射电镜及X光衍射的方法对聚乙烯醇修饰的碳纳米管在溶解过程中的显微结构变化进行了研究.结果表明:浸泡21d后,聚乙烯醇修饰的碳纳米管部分溶解于缓冲溶液,形成无定形碳碎片;但大部分碳纳米管没有溶解,仍然保持管状结构.揭示出聚乙烯醇修饰的碳纳米管的溶解过程为:碳-碳键在浸泡过程中发生断裂,碳纳米管的部分溶解产生了无定形碳碎片与残留纳米管层片,残留纳米管层片进一步溶解最终成为无定形碳.提出与讨论了聚乙烯醇修饰的碳纳米管在Tris-HCl缓冲溶液中可能的溶解机理是:修饰后的碳纳米管表面具有很多缺陷和断裂的碳键,在缓冲溶液中聚乙烯醇的溶解导致嫁接位置的碳管壁的碳原子的释放,最终导致其管状结构的破坏.

Dissolution of poly(vinyl alcohol)-modified carbon nanotubes in a buffer solution

Multiwalled carbon nanotubes(MWCNTs)were modified with a water-soluble poly(vinyl alcohol)(PVA)polymer(MWCNTs-PVA). The dissolution of the MWCNTs-PVA in Tris-HCl buffer solution was carried out in a shaking water bath by a soaking method. The microstructural changes of the MWCNTs-PVA during soaking was investigated using Fourier transform-infrared spectroscopy, differential scanning calorimetry, transmission electron microscopy, and X-ray diffraction. It is found that part of the MWCNTs-PVA was dissociated into amorphous carbonaceous debris, but most of tubular structures were retained after 21d of soaking. The dissolution process revealed that the C-C bonds of the MWCNTs-PVA were broken-down with the generation of carbonaceous debris and residual carbon nanotube la-yers, and the latter can be further dissociated into amorphous carbonaceous debris. A possible dissolution mechanism of the MWCNTs-PVA in the buffer solution was proposed and discussed. The surface modified MWCNTs have many defects and open C-C bonds on the surfaces of the CNTs. The dissolution of the PVA in the buffer solution leads to a release of carbon atoms on the outer surface of the MWCNTs. It results in a further rupture of the C-C bonds and destroys the tubular structure.