Inorganic–organic core–shell titania nanoparticles for efficient visible light activated photocatalysis

Nanostructured modified TiO2 (m-TiO2) was synthesized using the gel combustion method based on the calcination of an acidified alkoxide solution mixed with urea. The materials were characterized by Raman, FT-IR and UV–vis diffuse reflectance spectroscopies, transmission (TEM) and scanning electron microscopies (SEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR), in comparison with reference material untreated with urea (ref-TiO2). The effect of both the urea content and calcination temperature were optimized, providing the optimal absorption threshold of 2.19 eV for solar light harvesting. The photocatalytic performance of the m-TiO2 powder was tested for the degradation of methylene blue (MB) azo dye under UVA (350–365 nm), visible (440–460 nm), and daylight (350–750 nm) illumination. The hybrid inorganic/organic material shows exceptional physicochemical properties and significant photocatalytic activity, especially in the visible, attributed to sensitization of the TiO2 by a thin porous layer of carbonacious species in controlled core–shell morphology.

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► Combustion gel synthesis of composite titania photocatalysts.
► Optimization of urea content and calcination temperature.
► Core crystalline TiO2 uniformly covered by thin porous carbonaceous shell.
► Visible light activated EPR signals from organic radicals.
► High photocatalytic performance under visible light illumination.