Modulating Reactivity and Stability of Graphene Quantum Dots with Boron Dopants for Mercury Ion Interaction: A DFT Perspective

The objective of this study was to use Density Functional Theory (DFT) calculations to examine how boron doping modulates the electronic properties of graphene quantum dots (GQDs) and their interaction with the Hg2+ ion. Boron doping decreases the HOMO-LUMO gap and increases the GQD’s electrophilic character, facilitating charge transfer to the metal ion. The adsorption energy results were negative, indicating electronic stabilization of the combined systems, without implying thermodynamic favorability, with the GQD@3B_Hg2+ system being the strongest at −349.52 kcal/mol. The analysis of global parameters (chemical descriptors) and the study of non-covalent interactions (NCIs) supported the affinity of Hg2+ for doped surfaces, showing that the presence of a single boron atom contributes to clear attractive interactions. In general, configurations doped with 1 or 2 boron atoms exhibit satisfactory performance, demonstrating that boron doping effectively modulates the reactivity and adsorption properties of GQD for efficient Hg2+ capture.