Different Upconversion Properties of β-NaYF₄:Yb³⁺,Tm³⁺/Er³⁺ in Affecting the Near-Infrared-Driven Photocatalytic Activity of High-Reactive TiO₂

Abstract

Double-shell-structured β-NaYF4:Yb(3+),Tm(3+)/Er(3+)@SiO2@TiO2 upconversion photocatalysts have been successfully synthesized by a simple hydrothermal method. It is found that the double-shell-structured photocatalyst consists of uniform β-NaYF4:Yb(3+),Tm(3+)/Er(3+) nanocrystals, SiO2 as the media shell, and anatase TiO2 nanocrystals exposed with the high-reactive {001} facets as the outer shell. The TiO2 shell is modified to absorb both the UV and visible light in order to make sufficient use of the upconverted light from β-NaYF4:Yb(3+),Tm(3+)/Er(3+) for photocatalysis. Effective energy transfer from β-NaYF4:Yb(3+),Tm(3+)/Er(3+) to TiO2 and its importance are confirmed. The photocatalytic activity in the degradation of Rhodamine B (RhB) under the near-infrared (NIR) (980 nm laser) irradiation suggests that the NIR-driven photocatalytic activity of the double-shell-structured photocatalyst is significantly dependent on the properties of the upconversion materials and the irradiated NIR power density. Moreover, the NIR-driven photocatalyst shows stable photocatalytic degradation of RhB in the recycled tests. This study suggests a promising system and a new insight to understand the application of appropriate upconversion materials to effectively utilize the NIR for photocatalytic applications of TiO2-based photocatalysts, which may advance the application of solar energy in the future.

Synthesis of Reduced Grapheme Oxide as A Platform for loading β-NaYF4:Ho3+@TiO2Based on An Advanced Visible Light-Driven Photocatalyst

“…In order to efficiently utilize the valuable UC energy transferred from the excited UC core, a coupling model was proposed to increase the luminous efficiency, of which the core-shell structure has potential in protecting the UC core from surface quenching and in increasing the efficiency of transferring energy to the photocatalyst shell 25–28 . For examples, the preparation of (α, β)-NaYF 4 :Yb 3+ ,Tm 3+ @TiO 2 , YF 3 :Yb 3+ ,Tm 3+ @TiO 2 , and Y 2 O 3 :Yb 3+ has been reported, wherein the core-shell composite of UC@TiO 2 can emit UV and Vis and show an effective photocatalysis under NIR light 29–33 .…”

Extended Near-Infrared Photoactivity of Bi6Fe1.9Co0.1Ti3O18 by Upconversion Nanoparticles

“…Furthermore, compared with conventional fluorescent materials, such as organic dyes and quantum dots, upconversion nanoparticles have the following advantages: (i) High photostability and chemical stability; (ii) low toxicity to the human body; (iii) good biocompatibility by surface modification and functionalization; and (iv) good optical transparency over a wide wavelength range and low phonon energy [34,35,36,37]. Therein, coupling upconversion nanoparticles with photocatalysts is considered to bea very promising method to extend NIR photoactivity [38]. …”

Efficient up-conversion in Yb:Er:NaT(XO4)2 thermal nanoprobes. Imaging of their distribution in a perfused mouse

“…Within this approach, NPs with up-conversion (UC) properties are recognized fluorescence nanoprobes because they are free of photobleaching shown by organic dyes [1] or photoblinking of semiconductor quantum dots,[2] and their excitation in the near infrared (NIR) circumvent the problem of undesired tissue and cell autofluorescence typically observed under ultraviolet/blue photoexcitation. [3] Therefore, UCNPs have been extensively proposed for thermal nanosensing,[4,5] optical nanoencoding,[6] photocatalysis,[7] subcutaneous photodynamic therapy,[8,9] biosensing,[10] cancer cell recognition and treatment,[11] intracellular drug delivery,[9,12] as well as for in vitro and in vivo biomedical imaging. [9,13,14]…”