Double-Mode Thermometer Based on Photoluminescence of YbGd2Al2Ga3O12: Cr3+ Operating in the Biological Windows

A Near-Infrared (NIR) ratiometric luminescence thermometer with the composition of Yb1Gd2Al1.98Cr0.02Ga3O12 was prepared and studied. When excited by 660 nm in the first biological transparent window (BTW), the sample shows a peak structure of around 1000 nm due to the 2F5/2 → 2F7/2 transitions of Yb3+ via the energy transfer process from Cr3+. Due to the Boltzmann distribution, the Yb3+ PL intensities in the shorter wavelength side (i.e., 1st BTW) and longer wavelength side (i.e., 2nd BTW) exhibit opposite temperature dependencies. The luminescence intensity ratio (LIR) of Yb3+ in shorter and longer wavelength ranges works as a luminescence thermometer with a relative sensitivity of 0.55% K−1 at 310 K. In addition, YbGd2Al1.98Cr0.02Ga3O12 can also be employed for temperature sensing based on the LIR of Cr3+ (2E → 4A2) at around 700 nm and Yb3+ (2F5/2 → 2F7/2) at around 1000 nm, achieving a remarkable relative sensitivity of 2.69% at 100 K. This study confirms that the YbGd2Al1.98Cr0.02Ga3O12 thermometer fulfills the requirements for biological temperature measurements.

本研究制备并研究了组成为Yb₁Gd₂Al₁.₉₈Cr₀.₀₂Ga₃O₁₂的近红外（Near-Infrared, NIR）比率型发光温度计。当以第一生物透明窗口（Biological Transparent Window, BTW）内的660 nm光激发时，该样品通过Cr³+向Yb³+的能量传递过程，呈现出源于Yb³+²F₅/₂ → ²F₇/₂跃迁的约1000 nm处的发射峰结构。基于玻尔兹曼分布，Yb³+的光致发光（Photoluminescence, PL）强度在短波侧（即第一生物透明窗口）与长波侧（即第二生物透明窗口）呈现相反的温度依赖性。Yb³+在短波与长波波段的发光强度比（Luminescence Intensity Ratio, LIR）可作为发光温度计，在310 K时的相对灵敏度可达0.55% K⁻¹。此外，Yb₁Gd₂Al₁.₉₈Cr₀.₀₂Ga₃O₁₂还可基于Cr³+在约700 nm处的²E → ⁴A₂跃迁与Yb³+在约1000 nm处的²F₅/₂ → ²F₇/₂跃迁的发光强度比实现温度传感，在100 K时可获得高达2.69%的相对灵敏度。本研究证实，该Yb₁Gd₂Al₁.₉₈Cr₀.₀₂Ga₃O₁₂基温度计可满足生物体内温度测量的相关要求。