Structural, morphological, and photoluminescence properties of nitrogen-doped CNTs and graphitic carbon nanostructures.

Graphitic carbon nitride (g-C₃N₄) and carbon nitride nanotube (CNNTs) were synthesized by the pyrolysis-assisted chemical vapor deposition (PA-CVD)—pyrolysis method. The crystal structure, surface morphology, and photoluminescence properties of these materials were influenced by the deposition temperature and the choice of metal substrate. This study provides a detailed discussion of the structural growth of CNNTs and graphitic carbon nitride. As the temperature increases to 800 °C, the quantity of amorphous nature in the carbon structures increases along with an increase in the defect states. The d-spacing of interlayers of g-C₃N₄ and carbon nitride nanotubes (CNNTs) obtained from X-ray diffraction are 3.2 Ȧ and 3.3 Ȧ, respectively. The calculated crystallite size is about 87 nm for g-C₃N_4, and the lattice strain is 3.14. FESEM analysis shows a clear difference in the nanotube structures, CNNTs prepared at 600 °C have linear structures with a minimum of 60 nm diameters, whereas CNNTs prepared at 800 °C show spiral, knot, and irregular structures with a minimum of 40 nm diameter. In addition, the nano-level features and interplanar spacings are confirmed by HRTEM and SAED investigations. The maximum photoluminescence intensity observed at 574 nm and 579.5 nm for g-C₃N₄ on Cu substrate at 800 °C lies in the yellow light region. Additionally, smaller peaks were noted at higher wavelengths in the visible light spectrum. The estimated optical bandgap from the prepared samples from photoluminescence studies lies around 2.14 eV. [ABSTRACT FROM AUTHOR]