A computational dive into tuning nitrosourea adsorption on T-graphene nanosheets

This study examines the adsorption of a nitrosourea (NU) drug molecule onto pristine and doped T-graphene (TG) nanosheets, specifically those doped with boron (BTG) and aluminum (AlTG), utilizing density functional theory (DFT) at the M06-2X/6-31 + G(d,p) level of theory. We investigated the geometric, electronic, and energetic properties of the resulting complexes, focusing on adsorption energies, HOMO-LUMO gaps (E_g), molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis, and quantum theory of atoms in molecules (QTAIM). Our findings indicate that aluminum doping significantly enhances the adsorption of NU onto the TG nanosheet, exhibiting strong chemisorption as evidenced by a high adsorption energy (E_ads) of - 41.46 kcal mol^-1 and substantial charge transfer. However, this high adsorption energy results in a very lengthy desorption time of 2.3 × 10¹⁸ s. In contrast, boron doping increases the E_ads to a more manageable level (- 14.91 kcal mol^-1), leading to a recovery time of 8.3 × 10^-2 s, which is advantageous from a drug delivery perspective. Frontier molecular orbitals analysis revealed that the most prominent E_g change upon adsorption of NU occurs in the case of BTG with a 10.46% reduction. While the variations of E_g for TG-NU and AlTG-NU are - 1.31% and 5.20%, respectively. NBO analysis confirmed substantial donor-acceptor interactions in the AlTG-NU complex, while QTAIM indicated the presence of partially covalent interactions. Pristine TG and BTG exhibited weaker interactions with NU; however, the bonding nature remained partially covalent in both cases. The calculated recovery times further suggest that BTG provides a more favorable drug release profile compared to TG and AlTG. This study highlights the potential of boron-doped TG as an effective nanocarrier for drug delivery, underscoring the essential role of doping in tailoring the electronic and adsorption properties of graphene-based materials.