Intense Single Red Emission Induced by Near‐Infrared Irradiation Using a Narrow Bandgap Oxide BiVO₄ as the Host for Yb³⁺ and Tm³⁺ Ions

Abstract

As a new way of producing a single red emission under near‐infrared (NIR) irradiation, the possibility of using a narrow bandgap oxide as the host for the sensitizer Yb3+ ion as well as a suitable activator ion such as Ho3+, Er3+, or Tm3+ is considered, because the host can absorb the emissions of the activator ion higher in energy than the red emission. To verify this new concept, BiVO4:Yb3+,Tm3+ using a sol–gel method is prepared and its photoluminescence properties are characterized. BiVO4 has the bandgap of ≈2.4 eV so that, under NIR irradiation, it absorbs the blue and other higher‐energy emissions of Tm3+. As a consequence, BiVO4:Yb3+,Tm3+ exhibits an intense single red emission under the NIR irradiation. The high‐energy emissions absorbed by the host generate electron–hole pairs in the host, so that BiVO4:Yb3+,Tm3+ acts as a photocatalyst under NIR irradiation although the host alone cannot absorb the NIR light. NIR‐induced upconversion luminescence (UCL) and photocatalysis in the region of red lights can be achieved by employing a semiconducting oxide as the host for sensitizer and activator lanthanide ions.

Photocatalysis Driven by Near-Infrared Light: Materials Design and Engineering for Environmentally Friendly Photoreactions

“…BiVO 4 as the host for the dopants Yb 3+ and Tm 3+ to generate an intense single red emission and photocatalysis under NIR illumination. 105 As shown in Figure 7b, the experimental results show that nearly 90% of MB can be degraded by BiVO 4 :Yb 3+ ,Tm 3+ under NIR irradiation. Lozano-Sańchez et al prepared erbium-doped CaTiO 3 photocatalysts for photodegradation of MB.…”

“…Therefore, the latest research focuses on composite material based on NaYF 4 . Moreover, rare earth iondoped semiconductor photocatalysts have also aroused the extensive interest of researchers, such as Yb 3+ /Tm 3+ -codoped BiVO 4 , 105 erbium-doped CaTiO 3 , 106 and Yb 3+ /Tm 3+ -codoped In 2 S 3 . 107 Zheng et al prepared YF 3 :Yb 3+ ,Tm 3+ /TiO 2 core/shell NPs for photodegradation with NIR light.…”

“…(b) Photocatalytic degradation of MB in aqueous solution over various samples under NIR light. Reprinted with permission from Whangbo et al . Copyright 2018, Wiley-VCH.…”

“…Also, considering the appropriate band gap and the difficulty of synthesis, oxides and sulfides are also suitable candidates for host materials. Whangbo et al chose narrow band gap semiconductor BiVO 4 as the host for the dopants Yb 3+ and Tm 3+ to generate an intense single red emission and photocatalysis under NIR illumination . As shown in Figure b, the experimental results show that nearly 90% of MB can be degraded by BiVO 4 :Yb 3+ ,Tm 3+ under NIR irradiation.…”

Electronic Structure of Lanthanide-Doped Bismuth Vanadates: A Systematic Study by X-ray Photoelectron and Optical Spectroscopies

“…43 In a different context, Eu-doped BiVO 4 has attracted recent attention as materials for phosphor applications, 35 whereas Tm/Yb-co-doped BiVO 4 is of interest for up-conversion photoluminescence, whereby red emission from Tm 3+ is produced under near-infrared (NIR) excitation of the 2 F 7/2 → 2 F 5/2 transition in Yb 3+ . 44,45 Up-conversion has also been used to promote photocatalytic degradation of methylene blue under NIR irradiation using a Yb/Er/Tm co-doped BiVO 4 catalyst 46 and to increase the rate of photodegradation of rhodamine B by Nd/Er co-doped BiVO 4 . 47 Against this background, it is surprising that there has to date been no systematic study of the electronic properties of doped bismuth vanadate solid solutions across the whole lanthanide.…”