浓硝酸处理前后多壁碳纳米管的荧光特性研究

Studies on Fluorescent Properties of Multi-Walled Carbon Nanotubes before and after Concentrated Nitric Acid Treatment

对浓硝酸处理前后多壁碳纳米管的荧光特性进行了研究,结果发现多壁碳纳米管在浓硝酸处理前后都能产生荧光;与浓硝酸处理前相比,浓硝酸处理后的多壁碳纳米管的荧光有所增强,且荧光谱峰向短波长方向发生蓝移。碳纳米管产生的荧光与碳纳米管在其缺陷处捕获激发光的能量以及最低空轨道和最高占有轨道之间的能隙有关。多壁碳纳米管在浓硝酸处理前后都有缺陷,因而都能在其缺陷处捕获激发光能量而产生荧光;浓硝酸处理引起多壁碳纳米管的缺陷增多、捕获激发光能量增加因而荧光也随之增强。碳纳米管的最低空轨道和最高占有轨道之间的能隙随其长度减小而增大,浓硝酸处理引起多壁碳纳米管被削短导致其最低空轨道和最高占有轨道之间的能隙增大,因而引起多壁碳纳米管的荧光谱峰向短波方向蓝移。

Fluorescent properties of multi-walled carbon nanotubes (MWNTs) before and after concentrated nitric acid treatment were studied. The results show that both multi-walled carbon nanotubes (MWNTs) and treated multi-walled carbon nanotubes (t-MWNTs) could emit fluorescence; compared with MWNTs, fluorescence from t-MWNTs is stronger and fluorescent emission peak from t-MWNTs blue shifts slightly to short-wavelength. Luminescence from MWNTs could be related to the trapping of excitation energy at defect sites and the energy bandgap between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). Treating MWNTs with concentrated nitric acid could introduce more defects on MWNTs and make MWTNs trap more excitation energy, leading to a fluorescence enhancement of t-MWTNs; in addition, the energy bandgap between LUMO and HOMO increases with length decreasing of MWNT, and the shortening of MWNT caused by concentrated nitric acid treatment could make energy bandgap between LUMO and HOMO increase, resulting in a slight blue shift of fluorescent emission peak of t-MWTNs to short wavelength.