Er3+-to-Yb3+ and Pr3+-to-Yb3+ energy transfer for highly efficient near-infrared cryogenic optical temperature sensing

Nanothermometers based on Er³⁺-to-Yb³⁺ and Pr³⁺-to-Yb³⁺ energy transfer show very high performance in the near-infrared region in the cryogenic temperature regime.