Enhancement of caffeine adsorption on boron nitride fullerene by silicon doping

The physicochemical interaction between undoped- (B24N36; BNF) and silicon-doped boron nitride (B24N35Si; Si-BNF) fullerenes with caffeine was studied in the frame of the density functional theory (DFT). The influence of chemical composition in the capability of the fullerene to interact with caffeine was analyzed in terms of its structural stability, adsorption energy and charge distribution. The obtained results show that caffeine adsorption is enhanced by Si doping. The adsorption energy of caffeine molecule onto the BNF was calculated to be -0.26eV, whereas it was -0.33eV after doping. This effect is attributed to a rearrangement of the charge density driven by the substitutional defect (Si-N). After caffeine adsorption, an electron density displacement from the Si-BNF to the sorbate which stabilizes the caffeine/Si-BNF system is identified. Moreover, Si doping decreases the chemical hardness, while it induces a net spin angular momentum in the fullerene. The magnetic moment of the Si-BNF was determined in 1.0 mu(B), which does not vanish after caffeine adsorption. The physico-chemical parameters of the Si-BNF, along with its magnetic behavior, could favor using it as nanovehicle for drug delivery.