Multifunctional nanoparticles based on the Nd³⁺/Yb³⁺ codoped NaYF₄

Broadband near-infrared luminescence (NIR) from 720 to 950 nm, which is located in the biological window, has been successfully achieved from Nd³⁺/Yb³⁺ codoped hexagonal NaYF₄ nanoparticles when excited by 980 nm diode laser. Using the fluorescence intensity ratio technique, the temperature sensing behavior of Nd NIR emissions exhibits various advantages over other rare earth ion based nanothermometers. The light-induced thermal loading for the 980 nm excited NaYF₄:Nd³⁺/Yb³⁺ was also investigated. The results illustrate the multifunctionality of such fluoride nanoparticles, which could simultaneously act as the luminescent nanothermometers and nanoheaters and find potential application in photothermal therapy.