Functionalized multi-walled carbon nanotubes with strong fluorescence emission

Multi-walled carbon nanotubes (MWCNTs) with strong visible fluorescence were synthesized via oxidation and amination. A large number of oxygen-containing surface functional groups contributing to fluorescence emission have been found, and the novel structure of carbon nanoclusters with the diameter of 20-30 nm are formed at the tips of MWCNTs. The fluorescent MWCNTs exhibit distinct excitation-wavelength dependence and pH response. Furthermore, the temperature sensitivity of fluorescence has been described carefully. The fluorescence intensity first increases and then decreases upon increasing temperature, and the maximum emission is achieved when the functionalized MWCNTs are dried at 150 degrees C. (C) 2020 Elsevier B.V. All rights reserved.