Bi₂₀TiO₃₂ Nanoparticles Doped with Yb³⁺ and Er³⁺ as UV, Visible, and Near-Infrared Responsive Photocatalysts

In this work, we employed Yb3+ and Er3+ ions doped in a narrow bandgap oxide Bi20TiO32 to fabricate Bi20TiO32:Yb,Er, which can achieve near-infrared (NIR) responsive upconversion (UC) photocatalysis and produce a strong single red light. Because of the suitable bandgap of Bi20TiO32, strong green UC emission of Er3+ ions can be effectively absorbed by Bi20TiO32; thus, Bi20TiO32:Yb,Er can not only produce an intense single red emission but also generate electron–hole pairs with NIR irradiation. As a result, the as-prepared Bi20TiO32:Yb,Er exhibits excellent NIR photocatalytic activity, though Bi20TiO32 has no NIR response. The UC luminescence and the photocatalytic performances of as-prepared Bi20TiO32:Yb,Er can be optimized via changing the doping content of Yb3+ ions. Bi20TiO32:0.10Yb,Er exhibits the strongest single red emission and the highest NIR photocatalytic property. Under visible–NIR light (>420 nm) irradiation, the photocatalytic property of Bi20TiO32:0.10Yb,Er is almost twice of that for pristine Bi20TiO32. Our work demonstrates that Yb3+- and Er3+-doped narrow bandgap metal oxides could be potential candidates as intense single red light materials and highly efficient NIR responsive UC photocatalysts.