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In-situ Raman experiments together with transport measurements have been carried out on carbon nanotubes as a function of gate voltage. In metallic tubes, a large increase in the Raman frequency of the $G^-$ band, accompanied by a substantial decrease of its line-width, is observed with electron or hole doping. In addition, we see an increase in Raman frequency of the $G^+$ band in semiconducting tubes. These results are quantitatively explained using ab-initio calculations that take into account effects beyond the adiabatic approximation. Our results imply that Raman spectroscopy can be used as an accurate measure of the doping of both metallic and semiconducting nanotubes.
By heating H 3 BO 3 with urea in 1 : 6 molar ratio, nanoparticles and nanotubes of BN are obtained. The urea–boric acid reaction can also be exploited to obtain graphene analogues of BN, with the number of layers depending on the relative proportions of the two reactants. Synthesis with a high proportion of urea yields a product containing graphene analogues of BN with an average of 2 layers. The surface area of BN increases with the decreasing number of layers, and the high‐surface‐area BN also exhibits high CO 2 adsorption. Few‐layer BN can be solubilized by interaction with Lewis bases. Nanopans and nanosheets formed by graphene‐like BN are generated by the vapor phase reaction of NH 3 and BBr 3 at 1223 K. Nanopans of BN, being reported for the first time, have a bottom comprising single‐layer BN and a wall of 0.7 nm height. The average inner volume of the nanopan is around 400 nm 3 .
