Computational studies on the interaction of vitamin C (ascorbic acid) with nitrogen modified TiO2 anatase nanoparticles

Density functional theory calculations were performed to investigate vitamin C interaction with N-doped TiO2 anatase nanoparticles. The adsorption of vitamin C on the energy favorable fivefold coordinated titanium sites was investigated. Various adsorption geometries of vitamin C towards the nanoparticle were examined. Since the adsorption energies of N-doped nanoparticles are higher than those of undoped ones, the N-doped TiO2 nanoparticles can interact with vitamin C molecule more strongly. Besides, adsorption on the pristine nanoparticle is less favorable, whereas on the N-doped one, the adsorption process is more energy favorable. The electronic structure analysis was performed in view of the density of states and molecular orbitals of the considered nanoparticles with the adsorbed vitamin C molecule. The significant overlaps between the PDOS spectra of the oxygen atom of vitamin C molecule and titanium atom of TiO2 confirm the chemisorption of vitamin C on the TiO2 nanoparticle. After the adsorption, the electronic densities in the HOMOs of the adsorption systems were mainly distributed over the vitamin C molecule, while the LUMOs were dominant at the TiO2 nanoparticle. Our calculations shed light on understanding the interaction between vitamin C and TiO2 nanoparticles, which provides an efficient outline for future experimental studies.