Enhanced X-ray-induced luminescence and persistent luminescence of NaLuF4:Tb3+ nanoparticles with Li+ and Gd3+ co-doped

X-ray excitation photodynamic therapy is a new photodynamic therapy mode that induces tumor cell apoptosis by indirectly stimulating photosensitizer on nanoparticles with X-ray as excitation light source and generating singlet oxygen. It solves the problem of light penetration in traditional photodynamic therapy and realizes the treatment of deep tumors. At present, the weak X-ray-induced luminescence restricts further development of X-ray photodynamic therapy. NaLuF4:Li+/Gd3+/Tb3+ rare-earth nanoparticles with uniform size and regular morphology were synthesized by solvothermal method. The X-ray-induced luminescence intensity of NaLuF4:Li+/Gd3+/Tb3+ NPs was improved by Li+ and Gd3+ ions co-doping. The light yield of NaLuF4:Li+/Gd3+/Tb3+ NPs with 5% Li+ ions doping was 1.4 times than that of reference sample due to the change of crystal field symmetry. Furthermore, the effective lifetime of persistent luminescence increased from 221.5 s to 251.9 s after 15% Li+ ions doping. The thermoluminescence curves confirmed that the trap concentration was increased after Li+ ions doping, which was responsible for enhancing persistent luminescence lifetime. Long persistent luminescence emission laid a foundation for further application in photodynamic therapy.