Exploring the Potential of Chemically Modified Graphyne Nanodots as an Efficient Adsorbent and Sensitive Detector of Environmental Contaminants: A First Principles Study.

In this study, we investigated the reactivity of γ-graphyne (Gp) and its derivatives, Gp-CH ₃ , Gp-COOH, Gp-CN, Gp-NO ₂ , and Gp-SOH, for the removal of toxic heavy metal ions (Hg ^+ 2 , Pb ^+ 2 , and Cd ^+ 2 ) from wastewater. From the analysis of the optimized structures, it was observed that all the compounds exhibited planar geometry. The dihedral angles (C9-C2-C1-C6 and C9-C2-C1-C6) were approximately 180.00°, indicating planarity in all molecular arrangements. To understand the electronic properties of the compounds, the HOMO (E _H ) and LUMO (E _L ) energies were calculated, and their energy gaps (E _g ) were determined. The E _H and E _L values ranged between - 6.502 and - 8.192 eV and - 1.864 and - 3.773 eV, respectively, for all the compounds. Comparing the E _H values, Gp-NO ₂ exhibited the most stable HOMO, while Gp-CH ₃ had the least stable structure. In terms of E _L values, Gp-NO ₂ had the most stable LUMO, while Gp-CH ₃ was the least stable. The E _g values followed the order: Gp-NO ₂  < Gp-COOH < Gp-CN < Gp-SOH < Gp-CH3 < Gp, with Gp-NO ₂ (4.41 eV) having the smallest energy gap. The density of states (DOS) analysis showed that the shape and functional group modifications affected the energy levels. Functionalization with electron-withdrawing (CN, NO ₂ , COOH, SOH) or electron-donating (CH ₃ ) groups reduced the energy gap. To specifically target the removal of heavy metal ions, the Gp-NO ₂ ligand was selected for its high binding energy. Complexes of Gp-NO ₂ -Cd, Gp-NO ₂ -Hg, and Gp-NO ₂ -Pb were optimized, and their properties were analyzed. The complexes were found to be planar, with metal-ligand bond distances within the range of 2.092→3.442 Å. The Gp-NO ₂ -Pb complex exhibited the shortest bond length, indicating a stronger interaction due to the smaller size of Pb ^+ 2 . The computed adsorption energy values (E _ads ) indicated the stability of the complexes, with values ranging from - 0.035 to -4.199 eV. Non-covalent interaction (NCI) analysis was employed to investigate intermolecular interactions in Gp-NO ₂ complexes. The analysis revealed distinct patterns of attractive and repulsive interactions, providing valuable insights into the binding preferences and steric effects of heavy metals.
(© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)