Exploring the Sensing Potential of g-C₃N₄ versus Li/g-C₃N₄ Nanoflakes toward Hazardous Organic Volatiles: A DFT...

Ab initio calculations were performed to determine the sensing behavior of g-C₃N₄ and Li metal-doped g-C₃N₄ (Li/g-C₃N₄) quantum dots toward toxic compounds acetamide (AA), benzamide (BA), and their thio-analogues, namely, thioacetamide (TAA) and thiobenzamide (TAA). For optimization and interaction energies, the ωB97XD/6-31G(d,p) level of theory was used. Interaction energies (E_int) illustrate the high thermodynamic stabilities of the designed complexes due to the presence of the noncovalent interactions. The presence of electrostatic forces in some complexes is also observed. The observed trend of E_int in g-C₃N₄ complexes was BA > TAA > AA > TBA, while in Li/g-C₃N₄, the trend was BA > AA > TBA > TAA. The electronic properties were studied by frontier molecular orbital (FMO) and natural bond orbital analyses. According to FMO, lithium metal doping greatly enhanced the conductivity of the complexes by generating new HOMOs near the Fermi level. A significant amount of charge transfer was also observed in complexes, reflecting the increase in charge conductivity. NCI and QTAIM analyses evidenced the presence of significant noncovalent dispersion and electrostatic forces in Li/g-C₃N₄ and respective complexes. Charge decomposition analysis gave an idea of the transfer of charge density between quantum dots and analytes. Finally, TD-DFT explained the optical behavior of the reported complexes. The findings of this study suggested that both bare g-C₃N₄ and Li/g-C₃N₄ can effectively be used as atmospheric sensors having excellent adsorbing properties toward toxic analytes.