Exploring the Potential of Chemically Modified Graphyne Nanodots as an Efficient Adsorbent and Sensitive Detector of...

In this study, we investigated the reactivity of γ-graphyne (Gp) and its derivatives, Gp-CH₃, Gp-COOH, Gp-CN, Gp-NO₂, 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-NO₂ exhibited the most stable HOMO, while Gp-CH₃ had the least stable structure. In terms of E_L values, Gp-NO₂ had the most stable LUMO, while Gp-CH₃ was the least stable. The E_g values followed the order: Gp-NO₂ < Gp-COOH < Gp-CN < Gp-SOH < Gp-CH3 < Gp, with Gp-NO₂ (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, NO₂, COOH, SOH) or electron-donating (CH₃) groups reduced the energy gap. To specifically target the removal of heavy metal ions, the Gp-NO₂ ligand was selected for its high binding energy. Complexes of Gp-NO₂-Cd, Gp-NO₂-Hg, and Gp-NO₂-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-NO₂-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-NO₂ complexes. The analysis revealed distinct patterns of attractive and repulsive interactions, providing valuable insights into the binding preferences and steric effects of heavy metals.