Abstract：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.
Key words：Carbon nanotubes;Concentrated nitric acid;Fluorescence spectra;Infra red spectra;Raman spectrum;Defect
