Efficient visible-light-induced photocatalytic activity of a 3D-ordered titania hybrid photocatalyst with a core/shell structure of dye-containing polymer/titania

Photostable 3D-ordered titania hybrid photocatalyst with the core/shell structure of dye-containing polymer/titania was prepared by layer-by-layer coating of adsorption and hydrolysis of Ti(OBu)(4) on fluorescent polystyrene microspheres (YG), in which a sensitized dye of fluorescein isothiocyanate with a strong absorption in the visible light region of 400-500 nm is fixed. Photocatalytic tests show that the nanostructured titania hybrid photocatalyst exhibited efficient and stable photocatalytic activity for the photodegradation of crystal violet (CV) under visible light irradiation. The titania hybrid photocatalyst was characterized by UV-visible spectroscopy, SEM, TEM, XRD, photoluminescence (PL), time-resolved fluorescence, and electrochemical measurement. The characterization results show that the dye in YG spheres acts as a sensitizer for titania. By absorbing a visible photon it is promoted to an excited electronic state YG*, from which an electron can be injected into the conduction band of titania on the interface of YG spheres and titania shell. The electron subsequently induces the generation of active oxygen species, which result in the degradation of CV. The produced YG(+) radical cation can react with CV to realize the recycling of the photosensitized dye. The photodegradation of CV on TiO2-YG undergoes two competitive mechanisms: N-demethylation and destruction of the conjugated structure. The N-demethylation process predominates during the initial irradiation period. Later, the process of ring rupture is significant. It is evidenced that the N-didemethylated intermediate and the N-tridemethylated intermediate of CV undergo a direct cleavage of their conjugated structures.