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 Nd3+ 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.