Signature of aromatic carbons in the terahertz spectroscopy of bio-chars

The potential of terahertz spectroscopy in distinguishing aromatic carbon compounds in bio-chars is demonstrated. Several types of biochar samples were measured and compared with the THz spectra of pure aromatic compounds. Infrared spectra were modeled with B3LYP and mP2PLYP methods. Modeling could not identify accurately each of the absorption lines. However modeling shows that one of the lines close to 500 cm^-1 is due to vibrations of carbon rings, which can be used for identification of aromatic carbons in biochars.