Quantitative Assessment of the Amount of Material Encapsulated in Filled Carbon Nanotubes

In this paper, we present the first methodology for the quantitative assessment of the amount of material encapsulated in filled carbon nanotubes. Samples of single-walled carbon nanotubes have been filled by molten-phase capillary wetting with CuI, FeCl2, and CuBr. A suitable solvent has been used in each case to remove the large amount of external material present after the filling step. Thermogravimetric analyses in air have been performed to the empty and filled nanotubes, and the data have been used to obtain the filling yield for each sample. By using different starting nanotube samples, we stress the importance of the correct analysis of the data, which becomes more crucial for samples with larger quantities of metal catalyst impurities. High-resolution transmission electron microscopy and X-ray electron dispersive spectroscopy experiments confirm the encapsulation of the desired compounds into the single-walled carbon nanotubes and the absence of external metal halides. The method proposed herein is accurate, simple, and can be easily implemented for a large variety of materials.