SEM images of the as-grown MWNTs: (a) and (b) Undoped tubes of approximately 100 μm length. (c) and (d) Corrugated and shorter phosphorus doped MWNTs prepared with 0.2 wt. % of triphenylphosphine.
(a) TEM image of P-MWNTs obtained by the pyrolysis of ferrocene and triphenylphosphine in toluene showing a carbon necklace morphology. (b) HRTEM image of the graphitic planes responsible for the morphology of the nanotubes.
(Color online) X-ray diffraction pattern of (a) undoped MWNTs, (b)and (c) P-MWNTs at 0.2 and 0.3 wt. %, respectively.
(Color) Chemical elemental mapping of P-MWNTs by STEM-EDS. (a) STEM-HAADF image showing the presence of nanoparticles trapped in the inner part of the P-MWNTs. (b) Chemical elemental map showing the presence of P in the particles, and (c), (d) chemical elemental maps showing the presence of Fe and O in the particles, respectively.
(Color) Raman spectra of MWNTs. (a) The I D /I G ratio for the doped tubes at 0.15, 0.2, 0.25, 0.3, and 0.65 wt. % of triphenylphosphine. (b) G′ band of P-MWNTs obtained at a low laser power of 0.14 mW to avoid peak shifts by sample heating.
(Color) (a) XPS spectra of the phosphorus P 2p binding energy of the MWNTs produced at 0.3 wt. % of Ph3P. The inset shows the carbon C 1s binding energy of the same sample. (b) Deconvolution of the Fe 2p3/2 peak.
Comparison between the XPS spectra corresponding to P-MWNTs, triphenilphosphine and metallic red phosphorus (P-red), showing the different phosphorus binding energy for phosphorus atoms in different chemical environment.
XPS data of substitutional phosphorus on P-MWNTs.
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