Quantum Chemical Study on the adsorption of metformin drug on the surface of pristine, Si- and Al-doped (5,5) SWCNTs

Adsorption properties of metformin (MF) drug onto pristine, Si- and Al-doped (5, 5) armchair single-wall carbon nanotubes (SWCNTs) were studied using density functional theory (DFT) calculations at the B3LYP and omega B97XD methods with the standard 6-311 G** basis set. The most stable geometries of the MF drug molecule onto pristine, Si- and Al-doped (5, 5) CNTs were selected and evaluated in the gaseous and aqueous environments. We calculated the natural bond orbitals (NBO), Frontier molecular orbital (FMO), density of states (DOS) and molecular electrostatic potential (MEP) of systems upon adsorption of MF drug. It was found that the reaction of MF drug with pure SWCNT is physisorption in nature, while high chemisorption can be achieved by using Al- and Si-doped SWCNTs. Despite Al-doped SWCNT provides stronger adsorption, however the change in the energy gap of Si-doped SWCNT is more pronounced. It is predicted that MF drug incorporating Si-doped SWCNT can be extended as drug delivery system.