Red light intensity modulation, temperature sensing and bioimaging of NaLuF4:Er3+/Tm3+/Yb3+ microcrystals under 1532 nm laser excitation

This paper reports on microcrystals with deep tissue penetration depth, strong red light emission, and thermometric function. The red light emission of NaLuF ₄:20 % Er ³⁺/1 % Tm ³⁺/10 % Yb ³⁺ microcrystals is exceptionally strong, thanks to the introduction of Tm ³⁺ and Yb ³⁺ ions energy capture centers. In bioimaging, the 1532 nm laser exhibits deeper imaging depth due to weak photon scattering and autofluorescence. Furthermore, red light emission has the greatest tissue penetration depth in the visible region. The luminescence intensity and tissue penetration depth of both the excitation and emission light make them suitable for deep tissue imaging. We investigated temperature sensing performance of NaLuF ₄:20 % Er ³⁺/1 % Tm ³⁺/10 % Yb ³⁺ microcrystals, and found that the maximum relative sensitivity of LIR (I ₅₂₁/I ₅₄₀) reaches 0.92 %K ⁻¹. The microcrystals NaLuF ₄:20 % Er ³⁺/1 % Tm ³⁺/10 % Yb ³⁺ are anticipated to have application in deep tissue imaging and temperature sensing.