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Issue 28, 2015
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Non-ultraviolet photocatalytic kinetics of NaYF4:Yb,Tm@TiO2/Ag core@comby shell nanostructures

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Abstract

An effective near-infrared (NIR) active photocatalyst, NaYF4:Yb,Tm@TiO2/Ag (UC@TiO2/Ag) core@comby shell composite, was synthesized by a simple three-step hydrothermal process. Under the full-spectrum light of a Xe lamp in UV-Vis absorbance experiments, about 96% of R6G dyes in solution were degraded by UC@TiO2/Ag in 120 minutes, while only about 64% of the dyes were degraded by pure TiO2 under the same conditions. Under a UV-filtered Xe lamp, about 35% of the dyes were degraded by UC@TiO2/Ag in 120 minutes; interestingly, only about 8% of the dyes were degraded by pure TiO2. Under irradiation by a 785 nm laser in surface enhanced Raman scattering (SERS) experiments, the photodegradation rate constants were 0.02612 s−1 for UC@TiO2/Ag and 0.00046 s−1 for TiO2/Ag, indicating a nearly 58 fold improvement. After deducting the photobleaching effect, the photodegradation rate constants for UC@TiO2/Ag under 633 and 532 nm lasers were 0.00715 s−1 and 0.00565 s−1, respectively, revealing a sharp decrease under irradiation at shorter wavelengths. Electron spin resonance (ESR) analysis revealed that the presence of UC in this photocatalytic system certainly induced the increase of ˙OH free radicals with NIR irradiation, i.e. the UC core converts NIR light into ultraviolet (UV) light and initiates excellent photocatalytic activity of the TiO2/Ag comby shell. Furthermore, the decorating of Ag nanoparticles not only enhances the photocatalytic ability, but also provides a structural basis for monitoring the photocatalytic kinetics by the SERS technique. By virtue of monochrome laser lines, SERS analysis provides direct evidence to prove the capability of UC-initiated non-UV photocatalysis and the improvement of the utilization of non-UV lights on TiO2. The results revealed that this new photocatalytic platform can efficiently utilize different bands of the solar spectrum and also find new applications in SERS fields.

Graphical abstract: Non-ultraviolet photocatalytic kinetics of NaYF4:Yb,Tm@TiO2/Ag core@comby shell nanostructures

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Publication details

The article was received on 29 Apr 2015, accepted on 06 Jun 2015 and first published on 08 Jun 2015


Article type: Paper
DOI: 10.1039/C5TA03143E
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J. Mater. Chem. A, 2015,3, 14642-14650

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    Non-ultraviolet photocatalytic kinetics of NaYF4:Yb,Tm@TiO2/Ag core@comby shell nanostructures

    Y. Ma, H. Liu, Z. Han, L. Yang and J. Liu, J. Mater. Chem. A, 2015, 3, 14642
    DOI: 10.1039/C5TA03143E

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