Norfloxacin Adsorption on the Surface of Pristine and Si-Doped Fullerenes [C24 and SiC23]: A Comparative Theoretical Study

The performance of pristine and Si-doped fullerenes (C-24 and SiC23) as an adsorbent and sensing material for the removal and electrochemical detection of norfloxacin (NFX) was studied through density functional theory computations. The obtained adsorption energies showed NFX interaction with both adsorbents is experimentally feasible. The calculated thermodynamic parameters including triangle H-ad, triangle G(ad), triangle S-ad and K-th demonstrated NFX adsorption process on C-24 is spontaneous, exothermic, and one-sided but its interaction with SiC23 is also thermodynamically possible, two-sided, and equilibrium. The NBO results exhibited during the NFX adsorption process on C-24 some monovalent bonds have been created between the drug molecule and nanostructure and the interactions have a chemisorption nature. But in the case of SiC23, the NFX adsorption process was physisorption. The influences of temperature and solvent on the interactions were also scrutinized and the results showed NFX adsorption on the surface of both nanoadsorbents is more favorable at lower temperatures and the presence of solvent does not affect the interactions tangibly. The obtained DOS spectra demonstrated the bandgap of pristine fullerene increased +26.7% from 5.760 to 7.300 eV but in the case of Si-doped fullerene the bandgap of nanostructure experienced a -50.4% decline from 7.500 to 3.715 eV. The sharper changes of the bandgap for SiC23 indicated the Si-doped fullerene is a more suitable sensing material for the electrochemical detection of NFX and the very strong interactions that exist between C-24 and NFX showed the pristine fullerene is an appropriate adsorbent for the removal of this antibiotic.