Facile synthesis of Er3+/Yb3+-codoped NaYF4 nanoparticles: a promising multifunctional upconverting luminescent material for versatile applications

Abstract

The Er³⁺/Yb³⁺-codoped NaYF₄ upconverting nanoparticles were prepared by a facile hydrothermal method. Under the excitation of 980 nm, the obtained compounds exhibited the featured emissions of Er³⁺ ions. The optical thermometric performance of the Er³⁺/Yb³⁺-codoped NaYF₄ nanoparticles based on the thermally coupled ²H_11/2 and ⁴S_3/2 levels of Er³⁺ ions in the temperature range of 93–673 K was investigated by the fluorescence intensity ratio technique. The maximum sensitivity was approximately 0.0029 K⁻¹, indicating that both low- and high-temperature detection can be synchronously achieved in Er³⁺/Yb³⁺-codoped NaYF₄ upconverting nanoparticles. Furthermore, the temperature-dependent emitting color was discussed and it was changed from yellow to red with raising the temperature from 93 to 673 K. In addition, the internal heating properties of the developed nanoparticles caused by laser excitation power were also analyzed. It is found that the temperature of nanoparticles was elevated from 255.03 to 372.03 K with the increment of pump power from 84 to 585 mW. These characteristics suggest that the Er³⁺/Yb³⁺-codoped NaYF₄ upconverting nanoparticles are a promising candidate for optical temperature sensors and safety signs as well as optical heaters.