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, Gp-COOH, Gp-CN, Gp-NO, and Gp-SOH, for the removal of toxic heavy metal ions (Hg, Pb, and Cd) 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) and LUMO (E) energies were calculated, and their energy gaps (E) were determined. The E and E values ranged between - 6.502 and - 8.192 eV and - 1.864 and - 3.773 eV, respectively, for all the compounds. Comparing the E values, Gp-NO exhibited the most stable HOMO, while Gp-CH had the least stable structure. In terms of E values, Gp-NO had the most stable LUMO, while Gp-CH was the least stable. The E values followed the order: Gp-NO < Gp-COOH < Gp-CN < Gp-SOH < Gp-CH3 < Gp, with Gp-NO (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, COOH, SOH) or electron-donating (CH) groups reduced the energy gap. To specifically target the removal of heavy metal ions, the Gp-NO ligand was selected for its high binding energy. Complexes of Gp-NO-Cd, Gp-NO-Hg, and Gp-NO-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-Pb complex exhibited the shortest bond length, indicating a stronger interaction due to the smaller size of Pb. The computed adsorption energy values (E) 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 complexes. The analysis revealed distinct patterns of attractive and repulsive interactions, providing valuable insights into the binding preferences and steric effects of heavy metals.