Extremely intense red upconversion luminescence in Bi2O3:Yb3+/Er3+ for deep-tissue penetration along with photocatalytic performance

The upconversion luminescence (UCL) materials have the substantial advantages for deeper penetration and detection in tissue imaging and therapy owing to the dominant UCL wave located within the tissue optical transmission window. However, this application is limited by low red UCL efficiency. In this work, we synthesized Bi 2 O 3 : Yb 3+ /Er 3+ that exhibits intense red UCL under 980 nm excitation, which is about 5 times as that in conventional Y 2 O 3 sample. The red and green UCL intensity ratio is up to 229.6. Moreover, the red UCL can penetrate 8 mm fresh chicken breast tissue. Not only Bi 2 O 3 host exhibits excellent photocatalytic activity, Bi 2 O 3 : Yb 3+ /Er 3+ material also shows enhanced catalytic performance, achieving 91% degradation of methyl orange in 2 h under visible light (VIS). When combined with TiO 2 owned ultraviolet (UV) dominant activity, TiO 2 -modified Bi 2 O 3 : Yb 3+ /Er 3+ retains 96% activity under VIS. Furthermore, the degradation efficiency of Bi 2 O 3 : Yb 3+ /Er 3+ in the near-infrared (NIR) region can also reach 36% within 3 h, implying it is a promising candidate for UV–VIS–NIR broad-spectrum photocatalytic activity. Our study indicates that Bi 2 O 3 : Yb 3+ /Er 3+ is an outstanding multifunctional material that integrate strong red emission with capabilities for deep-tissue imaging and broad-spectrum-responsive photocatalysis.