Table_1_Effect of Mn2+ on Upconversion Emission, Thermal Sensing and Optical Heater Behavior of Yb3+ - Er3+ Codoped NaGdF4 Nanophosphors.DOCX

In thiswork, we investigate the influence of Mn²⁺ on the emission color, thermal sensing and optical heater behavior of NaGdF₄: Yb/Er nanophosphors, which the nanoparticles were synthesized by a hydrothermal method using oleic acid as both a stabilizing and a chelating agent. The morphology and crystal size of upconversion nano particles (UCNPs) can be effectively controlled through the addition of Mn²⁺ dopant contents in NaGdF₄: Yb/Er system. Moreover, an enhancement in overall UCL spectra of Mn²⁺ doped UCNPs for NaGdF₄ host compared to the UCNPs is observed, which results from a closed back-energy transfer between Er³⁺ and Mn²⁺ ions (⁴S_3/2 (Er³⁺) → ⁴T₁ (Mn²⁺) → ⁴F_9/2 (Er³⁺)). The temperature sensitivity of NaGdF₄:Yb³⁺/Er³⁺ doping with Mn²⁺ based on thermally coupled levels (²H_11/2 and ⁴S_3/2) of Er³⁺ is similar to that particles without Mn²⁺ in the 303–548 K range. And the maximum sensitivity is 0.0043 K⁻¹ at 523 K for NaGdF₄:Yb³⁺/Er³⁺/Mn²⁺. Interestingly, the NaGdF₄:Yb³⁺/Er³⁺/Mn²⁺ shows preferable optical heating behavior, which is reaching a large value of 50 K. These results indicate that inducing of Mn²⁺ ions in NaGdF₄:Yb³⁺/Er³⁺ nanophosphors has potential in colorful display, temperature sensor.