Molecules Immobilization in Titania Nanotubes: A Solid-State NMR and Computational Chemistry Study

Molecule immobilization in hydrothermally synthesized titania nanotubes is investigated by ¹³C solid-state NMR aided density functional theory calculations. The changes of ¹³C NMR spectra before and after immobilization indicate that phenols are chemisorbed and that aliphatic acid is possibly physisorbed in titania nanotubes. Hydroquinone exhibits monodentate bonds, and catechol exhibits bidentate bonds to accessible surface Ti sites in titania nanotubes. Immobilization of anthrarobin confirms that bidentate bonding is favored over monodentate bonding. Density functional calculations at the B3LYP/6-311+G(2d,p) level suggest that catechol is immobilized dissociatively via bridge bidentate bonding to neighboring surface Ti sites rather than chelate bidentate bonding to single surface Ti sites.