Syntheses and Study Structure, Morphology and Optical Properties of Carbon Nanotubes Doping by Cobalt Oxide (CoO) and Titanium Dioxide (TiO2)

Abstract

In this research two types of carbon nanotubes (CNTs) doping by cobalt oxide and carbon nanotubes doping by titanium dioxide were synthesized by chemical vapour deposition (CVD), the main objective of this research was to synthesize and determine structure, morphology and optical properties of carbon nanotubes doping by cobalt oxide (CoO) and titanium dioxide (TiO2) at different concentrations. Tenth samples of CNTs were prepared, five samples were doped by cobalt oxide at different concentrations (0.5, 0.75. 1.00, 1.25 and 1.50) and other five were doped by titanium dioxide at different concentrations (0.5, 0.75. 1.00, 1.25 and 1.50) in addition to the reference sample. X-ray diffraction (XRD) was used to obtain crystal structure and lattice parameters of samples, Scanning electron microscope (SEM) analysis was used to study surface morphology of the samples. UV-visible used to evaluate the optical parameters. The increasing on concentration on cobalt oxide and titanium dioxide leads to change structure parameter of carbon nanotubes samples (grain size, d-space, density and miller indices), the crystal types for all samples also changed due to concentration and molecular weight for doping element. For the optical properties the maximum value of absorbance is 1.83 (a.u) for CNTs + CoO (1.5) and the minimum value is 1.002 (a.u) at the same wavelength for reference sample while the maximum value of absorbance is 1.82 (a.u) at wavelength (258) nm for CNTs +TiO2 (1.5) and the minimum value is 0.99 (a.u) at the same wavelength for reference sample. CNTs+CoO and CNTs+TiO2 when to compare with the reference have same value of reflection 0.2 at different wavelengths in red shift because they have the same value of the polarization in different wavelengths. The optical energy band gap decrease with concentration increase according to atomic level convergence and this confirm with XRD results, the value of Eg for reference samples is 4.298 eV, CNTs+Co(1.50) is 3.613 eV and for CNTs+ TiO2 (1.50) is 3.333 eV. Finally, the average diameter of CNTs+CoO decreased from 29.736 nm for CNTs+CoO (0.5 molar) to 13.486 for CNTs+CoO (1.5 molar) and for CNTs+TiO2 decreased from 45.032nm for CNTs+TiO2 (0.5molar) to 21.951 nm for CNTs+TiO2 (1.5molar) while the diameter of reference sample is 51.21 nm, cobalt oxide reduced the average diameter of carbon nanotubes more than titanium dioxide.