研究目的
Investigating the improvement of graphene quantum dots' sensitivity towards toxic heavy metals (Cd, Hg, Pb) through nitrogen doping at vacant site defects for potential sensor applications.
研究成果
The study demonstrates that nitrogen doping at vacant site defects significantly improves the sensitivity of graphene quantum dots towards toxic heavy metals, with lead showing the highest adsorption energy. The findings suggest that nitrogen-coordinated defective GQDs could be promising materials for the development of sensors for heavy metal detection. The study provides a theoretical foundation for future experimental work in this area.
研究不足
The study is purely computational, and the findings need experimental validation. The model used (circumcoronene) may not fully represent the complexity of real-world graphene quantum dots. The study focuses on only three toxic heavy metals (Cd, Hg, Pb), and the findings may not be generalizable to other metals.
1：Experimental Design and Method Selection
Density functional theory (DFT) calculations were employed to investigate the adsorption of toxic heavy metals (THMs) on graphene quantum dots (GQDs) and nitrogen-coordinated defective GQDs. The M06-2X level of DFT with a 6-311G(d,p) basis set for carbon, nitrogen, and hydrogen atoms, and Def2-TZVPP basis set for the THMs was used. Grimme’s empirical dispersion correction (D3) was added to the M06-2X functional to investigate dispersion effects.
2：Sample Selection and Data Sources
A circumcoronene (C54H18) model was chosen as a model structure of GQDs. The GQD@1N, GQD@2N, GQD@3N, and GQD@4N models were constructed by removing carbon atoms from the basal plane and replacing them with nitrogen atoms at the created vacant sites.
3：List of Experimental Equipment and Materials
Computational simulations were performed using the Gaussian 09 package. No physical equipment was used as the study was computational.
4：Experimental Procedures and Operational Workflow
Initial structures for the interaction of THMs with the GQD and nitrogen-coordinated defective GQDs were constructed by placing the THMs directly on top of the surfaces. These complexes were allowed to relax without any force restraints. The adsorption energy, charge transfer, and other electronic properties were calculated post-optimization.
5：Data Analysis Methods
The adsorption energy was calculated using the counterpoise method to account for basis set superposition errors. Charge transfer was analyzed using ChelpG charge analysis. The nature of interaction was analyzed using the theory of atoms in molecules (AIM) and non-covalent interaction (NCI) plots. Time-dependent density functional theory (TDDFT) calculations were performed to analyze UV–visible absorption spectra.
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