表面官能化碳纳米管^(13)C NMR参数的理论研究

Theoretical Investigations of ^(13)C NMR Parameters of the Functionalized Carbon Nanotubes

碳纳米管表面化学修饰是当前研究的一大热点,修饰后由于极性基团的存在,碳纳米管在极性溶液环境中的分散度得到明显改善,这在很大程度上扩展了纳米管研究的应用范围.本文采用C80H20模型来表示(10,0)碳纳米管,基于此模型计算了一系列氮烯、卡宾和氟化的单壁纳米管的结构、偶极矩,以及核磁共振参数.研究表明高精度的密度泛函理论(DFT)计算能够用来预测纳米管的13C化学位移,理论研究的结果揭示了氮烯、卡宾以及1,2和1,4氟化的单壁纳米管的若干13C信号特征化学位移值,为实验NMR谱图的归属提供了一定的依据,并且可通过与实验相结合来监测表面官能化碳纳米管加成反应是否发生以及确认其加成方式.

Surface chemical modification of carbon nanotubes has become a hot research topic nowadays. The dispersion of carbon nanotubes in polar solvents can be greatly improved by attaching hydrophilic groups onto their surfaces, increasing the range of their application. In this study, a C80H20 model was used to represent the （10, O） zig-zag carbon nanotube. Based on this model, the structures, dipole moments and the nuclear magnetic resonance parameters were calculated for a series of funetionalized nanotubes, including nitrene and carbene modification, as well as 1, 2- and 1, 4-fluorination. The results indicated that the high level density functional theory （DFT） calculations can be used to predict the laC chemical shifts of the modified nanotubes. The calculated results also provided the characteristic chemical shifts values of nitrene-, carbene- and 1, 2- and 1,4-fluorinated nanotubes, which would be helpful for experimental spectrogram assignments. Combined with NMR experiments, these predicted characteristic chemical shifts can be further used to monitor the addition mechanism and the extent of surface modifications on nanotubes.