Mixed phase, sp2–sp3 bonded, and disordered few layer graphene-like nanocarbon: Synthesis and characterizations

We report on a method for the synthesis of Graphene-like nanocarbon (GNC) sheets. The obtained GNC contain mixed phase, sp2–sp3 bonded, and few atom layer of disordered carbon network. Initially, the mixture of soft wood charcoal (C), potassium nitrate (KNO3), and sulfur (S) was subjected to the combustion process. The obtained (as-synthesized) samples were intercalated (in H2SO4 (98%): HNO3 (60%), 48 h at 300 K) and subsequently annealed at 1000 °C for ∼60 s. The as-synthesized, intercalated, and annealed samples were studied using number of characterization techniques. The Raman spectra (at λ = 514 nm) recorded for the as-synthesized samples showed five prominent peaks, namely, for amorphous–Carbon (a–C), D doublet, small G, and 2D band. The position and intensity of the recorded peaks were varied for the intercalated and annealed samples. Our SEM analysis revealed that, the area of the GNC sheets varied typically in the range of 10 to 20 μm2. The analysis of HRTEM/SAED together showed that the intercalated samples contained a–C phase, whereas, short range ordering was observed for the annealed samples. The tunneling spectra recorded for the annealed GNC sheets showed V-shaped local density of states with the peak present near the minima. Our analysis revealed that, the sp2 chains and the polycyclic carbon rings (PCR) could be formed in the host ta–C matrix generating mixed sp2–sp3 bonded carbon network along with the local disorder. Details are presented.