Facile synthesis of pure TiO2(B) nanofibers doped with gold nanoparticles and solar photocatalytic activities
Pure and highly crystallized gold nanoparticles-doped-TiO2(B) nanofibers (Au-TBNFs), with thickness of 50–200 nm and length of several microns, were successfully synthesized by combination of low-temperature (150 °C) hydrothermal reaction of titanium (IV) isopropoxide (Ti[OC3H7]4) and sonication of the ensued precipitate with gold nanoparticles followed by post-heat treatment at 300 °C. Formation of pure TiO2(B) was confirmed by X-ray diffraction, high resolution transmission electron microscopy and Raman spectroscopy. The UV–vis diffuse reflectance spectra (DRS) of Au–TiO2(B) nanofibers exhibited surface-state absorption beyond 400 nm with band gap energy at 2.94 eV and broad gold plasma resonance band around 550 nm. The photoluminescence (PL) emission spectra of the Au-TBNFs exhibited structural emission band around 410 nm with shoulders around 464 nm and 540 nm. Analysis of these optical properties revealed that the surface state absorption is attributed to the indirect transition. These results suggest that coupling of the surface charge carriers with the lattice phonon of Au-TBNFs is so strong that the charge recombination is mostly nonradiative as supported by the significantly quenched emission of Au-TBNFs as compared to that of free TBNFs. These optoelectronic properties were well correlated with highly efficient solar photocatalytic activities of Au-TBNFs for oxidation of methylene blue (MB).
Graphical abstract.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We develop a new facile synthetic route for purely crystallized TiO2(B) nanofibers. ► We examine the optoelectronic natures of free and Au-doped TiO2(B) nanofibers (Au-TBNF). ► Au-doping increases visible light absorption and long-lived charge-separation. ► The solar photocatalytic efficiency of Au-TBNF is greater than that of anatase analogs. ► Au-TBNF would be very useful as an environmentally sustainable solar photocatalysts.
Journal: Applied Catalysis B: Environmental - Volumes 111–112, 12 January 2012, Pages 502–508