{'fraction_non_alphanumeric': 0.03863751906456533, 'fraction_numerical': 0.0066090493136756485, 'mean_word_length': 5.074074074074074, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Chemically induced, thermally controlled peel-off of the external walls of double-walled carbon nanotubes.

Double-walled carbon nanotubes (DWNTs) bridge the gap between the much-explored materials of single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). DWNTs possess coaxial structures, containing two concentric graphene cylinders. Apparently, due to their unique morphology, and since the inner tube in a typical DWNT has a typical diameter of 0.7 nm, DWNTs are particularly attractive because the inner tube is well protected from the external environment, representing a shielded “fl awless” SWNT with a narrow diameter. Techniques for preparing DWNTs generally produce mixtures of DWNTs and SWNTs concomitant with residual metal particles, amorphous carbon, as well as MWNTs. [ 1 ] However, if the DWNTs are grown from a peapod precursor material, namely from C 60 -peapods (C 60 @SWNTs) transformed at elevated temperatures upon fusion of the encapsulated C 60 to DWNTs, they exhibit a high degree of perfection due to the apparent growth in a highly protected domain. [ 2 ] Recently, the controlled production of high-quality DWNTs with uniform lengths and diameters and, importantly, which were free from metal and/or carbonaceous impurities having minimized the presence of other types of nanotubes (i.e., SWNTs, MWNTs), was successfully performed. [ 3 ] This is an important improvement for the chemistry and physics of DWNTs as it allows the identifi cation without doubt of spectroscopic signals in the Raman and UV–vis–NIR spectra, corresponding to the material and not to impurities present in minor quantities [ 4 ] (i.e., SWNTs, amorphous carbons, and metal catalyst particles). In the same context, the electronic transport properties of DWNTs have been investigated by constructing them as fi eld-effect transistor devices, indicating both pand n-type behavior in contrast with the known p-type behavior of SWNTs. [ 5 ]