Synthesis, Cytotoxicity Assessment and Optical Properties Characterization of Colloidal GdPO₄:Mn²⁺, Eu³⁺ for High...

Herein, a novel synthesis method of colloidal GdPO₄:Mn²⁺,Eu³⁺ nanoparticles for luminescent nanothermometry is proposed. XRD, TEM, DLS, and zeta potential measurements confirmed the crystallographic purity and reproducible morphology of the obtained nanoparticles. The spectroscopic properties of GdPO₄:Mn²⁺,Eu³⁺ with different amounts of Mn²⁺ and Eu³⁺ were analyzed in a physiological temperature range. It was found that GdPO₄:1%Eu³⁺,10%Mn²⁺ nanoparticles revealed extraordinary performance for noncontact temperature sensing with relative sensitivity S_R = 8.88%/°C at 32 °C. Furthermore, the biocompatibility and safety of GdPO₄:15%Mn²⁺,1%Eu³⁺ was confirmed by cytotoxicity studies. These results indicated that colloidal GdPO₄ doped with Mn²⁺ and Eu³⁺ is a very promising candidate as a luminescent nanothermometer for in vitro applications.