Polycyclic aromatic hydrocarbons (PAHs) persist in the environment due to their chemical stability, toxicity, and resistance to conventional remediation processes. This study investigates the electronic reactivity and adsorption potential of selected PAHs such as anthracene, benzo[a]pyrene, fluorene, naphthalene, and pyrene using density functional theory (DFT) and molecular docking approaches. Frontier molecular orbital calculations revealed that PAHs with smaller HOMO–LUMO gaps exhibited greater reactivity and more negative Gibbs free energy values, indicating enhanced thermodynamic favorability for adsorption. Benzo[a]pyrene showed the highest reactivity (HOMO–LUMO gap = 7.26 eV) and the most negative Gibbs free energy (–25.60 kcal/mol), suggesting its strong electron-accepting tendency. Binding energy analysis of PAH adsorption onto amine-functionalized carbon nanotubes (CNT–NH₂) further confirmed benzo[a]pyrene as the most strongly adsorbed molecule (E_bind = − 29.8 kcal/mol). Molecular docking of PAHs with a CNT–enzyme (Bacillus spp. laccase, PDB: 9BD5) complex demonstrated high docking scores and extensive hydrophobic and π–π stacking interactions, indicating a synergistic remediation mechanism driven by nanoparticle adsorption and enzymatic affinity. The combined DFT and Molecular docking results demonstrate that functionalized CNTs coupled with bacterial enzymes offer a highly effective platform for PAH remediation through dual adsorption and catalytic pathways.

Polycyclic aromatic hydrocarbons (PAHs) persist in the environment due to their chemical stability, toxicity, and resistance to conventional remediation processes. This study investigates the electronic reactivity and adsorption potential of selected PAHs such as anthracene, benzo[a]pyrene, fluorene, naphthalene, and pyrene using density functional theory (DFT) and molecular docking approaches. Frontier molecular orbital calculations revealed that PAHs with smaller HOMO–LUMO gaps exhibited greater reactivity and more negative Gibbs free energy values, indicating enhanced thermodynamic favorability for adsorption. Benzo[a]pyrene showed the highest reactivity (HOMO–LUMO gap = 7.26 eV) and the most negative Gibbs free energy (–31.80 kcal/mol), suggesting its strong electron-accepting tendency. Binding energy analysis of PAH adsorption onto amine-functionalized carbon nanotubes (CNT–NH₂) further confirmed benzo[a]pyrene as the most strongly adsorbed molecule (E _bind = − 26.75 kcal/mol). Molecular docking of PAHs with a CNT–enzyme ( Bacillus spp . laccase, PDB: 9BD5) complex demonstrated high docking scores and extensive hydrophobic and π–π stacking interactions, indicating a synergistic remediation mechanism driven by nanoparticle adsorption and enzymatic affinity. The combined DFT and Molecular docking results demonstrate that functionalized CNTs coupled with bacterial enzymes offer a highly effective platform for PAH remediation through dual adsorption and catalytic pathways.

The research work based on computational studies of copper dimethyl-bipyridine complexes, a set of computational calculations were computed with orca program using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods for (Cu(bipyridine) ₂ ⁺ & Cu(bipyridine) ₂ ²⁺ ) complexes. The calculation outputs were visualized using Avogadro software and charge decomposition analysis was performed using multwfn software. The results showed that the Highest Occupied Molecular Obital (HOMO) is delocalized over the copper and nitrogen atom on the ligands for Cu(bipyridine) ₂ ⁺ and Cu(bipyridine) ₂ ²⁺ . The Lowest Unoccupied Molecular Orbital (LUMO) is delocalized over the bi-pyridine ligands. Each of the complexes are divided into two fragments: copper ion portion designated as fragment 1 and the dimethyl-bi-pyridine ligand portion designated as fragment 2. The results of intra-fragment analysis shows that all the peaks have hole and electron contributions concentrated on separate fragments for Cu(bipyridine) ₂ ⁺ . While for Cu(bipyridine) ₂ ²⁺ the results shows that peaks 6, 5 & 8 have hole and electron contributions concentrated on separate fragments. The electron excitation analysis revealed that all the first five transitions in Cu(bipyridine) ₂ ⁺ are in the visible region, while Cu(bipyridine) ₂ ²⁺ , the first five transitions are in the infrared region. The calculated LHE value of the Cu(bipyridine) ₂ ⁺ dye at ground state was 0.123, while at the oxidized state (Cu(bipyridine) ₂ ²⁺ ) the LHE was 0.561. Molecular engineering of the complexes towards optimum positioning of its LUMO and HOMO with respect to CB of TiO ₂ and standard potential of the iodide/triiodide redox couple, will enhance its suitability for DSSC application.