Cr3+掺杂F-修饰BaScO2F钙钛矿结构宽带近红外荧光粉

Broadband Near-Infrared Phosphors Based on Cr3+-Ddoped and Anionic F- Modified Perovskite BaScO2F

摘要:

Cr³⁺掺杂的近红外荧光材料，因具有高量子效率、可调的宽带发射及在蓝色光谱范围内的强吸收特性而备受关注。通过晶体场工程，可以调节Cr³⁺掺杂的近红外荧光材料的发射范围，但常规的阳离子取代对发射范围的调节通常限制在近红外I区（波长<1 000 nm）。在生物医学成像领域，由于生物组织的吸收、散射和自发荧光较低，在近红外II区，能够实现更高的穿透深度及无创或微创的深部组织成像。采用高温固相法，以Ba₂Sc₂O₅类钙钛矿型氧化物为基体，合成了一系列基于F^-修饰的近红外荧光粉BaSc_1-xO₂F∶xCr³⁺（x=0.001—0.01）。通过XRD图谱和容差因子计算，证明了合成的样品具有立方钙钛矿结构。另外，通过漫反射光谱(DRS)和X射线光电子能谱（XPS）等表征手段，确认了Cr离子的价态为Cr³⁺。利用电子顺磁共振（EPR）对Cr³⁺周围的晶体环境进行检测分析发现，样品在波长700—1 400 nm范围内表现出近红外宽带发射，发射中心约在1 040 nm处，半峰宽(FWHM)高达250 nm。表明，Cr³⁺的发射有效覆盖了近红外II区。同时，也证明了通过阴离子掺杂调节晶体场强度是可行的。由于PLE光谱和PL光谱在波长700—850 nm范围内存在重叠，随着Cr³⁺掺杂浓度的增加，发射部分被重吸收，导致发射中心出现明显的红移现象。由于BaSc_1-xO₂F∶xCr³⁺近红外荧光粉的吸收峰与蓝光LED芯片能够匹配，表明其具有商业化潜力。本研究为生物医学成像领域的近红外II区荧光粉转换LED器件提供了优异的宽带近红外光源材料。

Abstract:

Cr³⁺-doped near-infrared （NIR） luminescent materials have attracted significant attention due to their high quantum efficiency， tunable broadband emission， and strong absorption in the blue spectral range. The emission range of Cr³⁺ can be adjusted through crystal field engineering， but conventional cation substitution limits this turning to the NIR I-region （<1 000 nm）. In the field of biomedical imaging， the NIR II region offers lower absorption， tissue scattering， and autofluorescence， allowing for deeper tissue penetration and minimally or non-invasive imaging. In this study， a series of Cr³⁺ doped NIR phosphor materials BaSc_1-xO₂F∶xCr³⁺（x=0.001—0.01）， were synthesized by high-temperature solid-state reaction method based on Ba₂Sc₂O₅ oxides with anionic F substitution. The synthesized samples exhibited a cubic perovskite structure as confirmed by XRD patterns and tolerance factor calculations. The Cr ions were verified to be in the +3 valence state using diffuse reflectance spectroscopy （DRS） and X-ray photoelectron spectroscopy （XPS）. Electron paramagnetic resonance （EPR） was employed to analyze the crystal environment around Cr³⁺. The samples displayed broadband NIR emission in the wavelength range of 700—1400 nm， with a full width at half maximum （FWHM） of up to 250 nm and an emission center around 1 040 nm， effectively covering the NIR II region. The study demonstrates the feasibility of modulating the crystal field strength by anion doping based on the relationship between internal structure and optical properties. Due to the overlap between the photoluminescence excitation （PLE） and photoluminescence （PL） spectra （700—850 nm）， increasing doping concentration led to partial reabsorption and a significant redshift of the emission center. The absorption peaks of the phosphor roughly match with blue LED chips， indicating commercial potential. This work provides excellent broadband near-infrared light source materials for NIR II region phosphor-converted LEDs （pc-LEDs） in biomedical imaging applications.