Electronic and optical properties of the express purified SWCNTs produced by HiPCO process
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Single-walled carbon nanotubes have been synthesized by a gas-phase CO decomposition (HiPCO) process, involving high-pressure disproportionation of CO as carbon feedstock and catalytic iron particles were obtained from pyrolysis of Fe(CO)5. The diameter and diameter distribution of as grown material dependents on various parameters, the strong is the pressure of CO cold transverse the Fe(CO)5, nozzle geometry and position for the injection of the reactant in the reaction chamber to produce smaller diameter (about 0.9 nm) at higher CO pressure. The HiPCO materials containing iron were purified by a two-step process of oxidation in oxygen atmosphere and successive washing the mixture of hydrochloric and nitric acids neutralised and distilled water (1:1:1). The optical and electronic properties were studied using optical absorption and infrared spectroscopy; in addition, high-resolution transmission electron energy-loss spectroscopy was used to analyse the loss function, electron diffraction and core level excitations. The degree of purification achieved was estimated using transmission electron microscopy. Furthermore, the present procedure has a no sufficiently change in the diameter and diameter distribution after Gaussian fit of the optical absorbance spectra. The estimation of the degree of purification is possible by the analysis of core level excitation; finally high purity SWCNTs were obtained.