Preparation of carbon nanotubes with high filling rate of copper nanoparticles

Performance of carbon nanotubes (CNTs) can be adjusted by filling their cavities with guest materials. In this study, Cu nanoparticles are filled into CNTs via wet chemical method. To improve the filling efficiency, oxygen-containing functional groups (OCFGs) are introduced onto the tube walls of CNTs by acid treatment. The defects and pore size distribution on CNTs are detected and quantified by N2 adsorption-desorption experiment, Raman spectra, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Morphologies of CNTs before and after filling treatment are observed by transmission electron microscope (TEM). The filling rate is characterized by inductively coupled plasma emission spectrometer (ICP) and thermal gravimetric analysis (TGA). The results indicate that the OCFGs can not only improve the hydrophilicity of CNTs, but also greatly affect the filling rate of CNTs. The filling rate of CNTs acid-treated for 24 h (1.99 wt% tested by TGA) is significantly lower than that of acid-treated for 8 h (12.11 wt% tested by TGA), which can be ascribed to the fact that excessive OCFGs could hinder Cu2+ ions from entering the cavity of CNTs. The obtained results can provide a new perspective for the application of CNTs in composite preparation and related fields.