Temperature-Dependent Over-1000 nm Near-Infrared Ho3+/Er3+ Luminescence Intensity Ratio of NaYF4: Yb3+, Ho3+, Er3+ Nanothermometer in Deeper Abdominal Region in Mice
Description
We investigated in vivo deep temperature sensing using β-NaYF4 nanoparticles co-doped with Yb3+, Ho3+, and Er3+ displaying two emission peaks in the >1000 nm near-infrared wavelength region, (i) Ho3+ emission at 1150 nm and (ii) Er3+ emission 1550 nm, where the scattering and absorption of light by biological tissues are at the minimum. The temperature sensing is based on the change in the luminescence intensity ratio (LIR) of the Ho3+ and Er3+ emission peaks (IHo/IEr) under 980-nm laser excitation as a function of temperature. The LIR of the NaYF4: Yb3+, Ho3+, Er3+ nanothermometer was found to differ according to the thickness of the tissue, necessitating the calibration of the relationship between IHo/IEr ratio and temperature according to the depth of the nanothermometer in vivo. Further, we demonstrate the temperature-dependent change in the IHo/IEr at the peritoneal cavity level, which is deeper than the subcutaneous tissue level, for the first time.