Abstract
The core-shell NaYb0.99F4:Tm0.01@NaYF4 upconverting particles (UCPs) with a high UV emission to apply in NIR-driven photocatalysis were synthesized. The influence of the Yb3+ doping concentration in NaYxF4:Yb0.99−xTm0.01 core particles, and the role of the NaYF4 shell on the upconversion emission intensity of the UCPs were studied. The absorption of NIR light by the obtained UCPs was maximized by increasing the Yb3+ concentration in the core, reaching the maximum for Y3+-free particles (NaYb0.99F4:Tm0.01). Additionally, covering the NaYb0.99F4:Tm0.01 core with a protective layer of NaYF4 minimized the surface luminescence quenching, which significantly improved the efficiency of upconversion emission. The high intensity of the UV light emitted by the NaYb0.99F4:Tm0.01@NaYF4 under NIR irradiation resulted in a high photocatalytic activity of TiO2 (P25) mixed with the synthesized material.
Highlights
Photocatalysis is a feasible solution for the emerging environmental and economic issues of humankind
4 29% to 99%) in the structure of the core particles on the emission intensity of the upconverting this work, we demonstrate the influence of the molar concentration of the Yb3+ ions
The crystals with the highest upconversion photoluminescence intensity were chosen to be coated with a protective NaYF4 layer in order to assess the outer shell influence on their luminescent properties
Summary
Photocatalysis is a feasible solution for the emerging environmental and economic issues of humankind. Most of the solar radiation that reaches the Earth’s surface lies within the visible and infrared region. Conventional photocatalysts, such as TiO2 or ZnO, while cheap, non-toxic, and chemically stable, absorb only ultraviolet (UV) light, which constitutes less than 5%. The photocatalytic systems based on the upconverting particles (UCPs) suffer from a low efficiency [11]. This is because the upconversion (UC) is a multiphoton nonlinear process that requires high power density of the incident light and is sensitive to any luminescence quenching and cross de-excitation [12,13]. Much effort is put into research to increase the efficiency of the UC processes occurring in materials suitable for photocatalytic applications
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