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.