DFT insights into indole detection and removal using aluminum and zinc doped coronene

Moteb Khobrani, Mohammed Ghazwani, Umme Hani, Yahia Alghazwani

Abstract The detection of Indole (IND) is crucial due to its biological and environmental significance. This study employs density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to investigate the adsorption behavior, electronic structure modifications, and sensing performance of pristine coronene (CRN) versus aluminum-doped (Al-CRN) and zinc-doped (Zn-CRN) coronene toward IND. All calculations were performed using ωB97XD and M06-2X functionals with the 6-311G(d) basis set, incorporating CPCM solvation (water) and gas-phase models for comparative analysis. Metal doping significantly reduced the HOMO-LUMO gap from 7.34 eV (CRN) to 6.00 eV (Al–CRN) and 4.95 eV (Zn-CRN), enhanced electron-accepting capability, and increased chemical softness. The adsorption energies followed the following order: CRN@IND (– 11.47 kcal/mol) < Al-CRN@IND (– 42.10 kcal/mol) < Zn-CRN@IND (– 82.51 kcal/mol), where Zn-CRN showed a stronger interaction. QTAIM analysis revealed increased electron density at metal-N bond critical points (ρ = 0.049 a.u. for Al-N; ρ = 0.080 a.u. for Zn-N) compared to weak CRN-IND interactions (ρ ≈ 0.006–0.007 a.u.). NCI/RDG, ELF, and LOL analyses confirmed the transition from weak van der Waals forces in CRN@IND to strong dative coordination interactions in doped systems. TD-DFT analysis showed that Al-CRN, after absorbing IND, produces a significant color change from the UV region (307 nm) to the visible region (415 nm), which can allow detection with the naked eye. Electrical conductivity analysis showed that Zn-CRN exhibits significant electronic disorder after IND binding, which can be considered for further investigation as an electrochemical sensor in the future. The calculated recovery times indicate effectively irreversible adsorption on doped surfaces, positioning these materials as promising candidates for single-use sensing, irreversible capture, and analyte removal applications rather than reusable sensors. These findings provide a theoretical basis for the synthesis of CRN-based nanomaterials for IND detection and environmental remediation.