Abstract
The Ag-nanoparticles (Ag-NP)/TiO2 composite thin films with various amounts of Ag (10 mol% ≤ n ≤ 80 mol%) were examined as a potential photocatalyst by decoloration reaction of methylene blue (MB) in an aqueous solution. These composite thin films of ca. 100 nm thickness were fabricated by the MPM at 600 °C in air. The decoloration rates monitored by the absorption intensity of the MB solution indicated that the composite thin films of Ag with an amount less than 40 mol% are not effective under vis-irradiation, though they can work as a photocatalyst under UV-irradiation. Further, the UV-sensitivity of the composite thin films gradually decreased to almost half the level of that of the TiO2 thin film fabricated under the identical conditions when the Ag amount increased from 10 to 40 mol%. Contrarily, the composite thin films of Ag content larger than 50 mol% showed the vis-responsive activity, whose level was slightly lower than the decreased UV-sensitivity. Diffuse reflectance spectra suggested that the vis-responsive activity of the composite thin films is due to the conductivity, localized surface plasmon resonance and surface plasmon resonance of Ag-NP. It was also elucidated that the vis-responsive level of the composite thin films corresponds to their electrical conductivity that depends on the Ag content.
Highlights
Metal oxide photocatalytic degradation of organic pollutants has attracted significant attention by researchers because of its usefulness in tackling environmental contaminants [1]
We report the photocatalytic activity of Ag-NP/TiO2 composite thin films with various amounts of Ag (10≤ Ag mol% ≤ 80) in titania and compare them with pure TiO2 thin film, both fabricated by the molecular precursor method (MPM)
The photocatalytic activity of the Ag-NP/TiO2 composite thin films including those of unprecedentedly high Ag amounts was quantitatively examined by the decoloration reaction of methylene blue (MB) in an aqueous solution
Summary
Metal oxide photocatalytic degradation of organic pollutants has attracted significant attention by researchers because of its usefulness in tackling environmental contaminants [1]. Its utilization remains typically confined to UV light because of its wide band gap (3.2 eV for anatase and 3.0 eV for rutile) [2] This limits the efficient utilization of solar energy for TiO2 because TiO2 cannot efficiently utilize solar light since UV light accounts for only 4–6% of solar radiation. One of the alternative approaches for achieving the threshold of the photo-response of TiO2 into the visible region is to make a composite semiconductor by modifying TiO2 with noble metals. These noble metals act separately or simultaneously depending on the photoreaction conditions, experimental methods used and they may (i) enhance the electron-hole separation by acting as electron traps [8,9,10,11],
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