Synthesis and characterization of finely dispersed phosphors doped with rare-earth metal ions for enhanced photodynamic therapy of cancer

Finely dispersed NaBaPO 4 :Eu 2+ , NaGdF 4 :Eu 3+ , BaGdF 5 :Eu 3+ , GdF 3 :Yb 3+ , Er 3+ and YF 3 :Yb 3+ , Er 3+ phosphors are synthesized using a sol–gel procedure and hydrothermal method. A process is developed for obtaining NaBaPO 4 :Eu 2+ phosphors with enhanced dispersion via sol–gel precipitation followed by a high-temperature annealing in molten NaCl. The applied annealing technique provided a 3.8-fold decrease in the phosphor particle size and 11-fold increase in the finely dispersed (less than 1 μm) fraction compared with the phosphors prepared using a conventional sol–gel method. In addition to already known luminescence centers comprising Eu 2+ ions located in NaBaPO 4 lattice sites with coordination numbers 10 and 12, these phosphors are found to contain two more types of luminescence centers supposedly corresponding to Eu 2+ ions in the same positions locating on the phosphor particle surface. According to the obtained data, the energy levels of luminescence centers in the NaBaPO 4 :Eu 2+ phosphor are summarized in a chart. NaGdF 4 :Eu 3+ phosphor is shown to be mostly appropriate for X-ray stimulated photodynamic therapy (PDT), while GdF 3 :Yb 3+ , Er 3+ phosphor is promising for IR-activated PDT. The efficiency of 980 nm IR laser-induced generation of active oxygen by a medicine involving the YF 3 :Yb 3+ , Er 3+ phosphor, and Radachlorin photosensitizer is studied. Graphic abstract A finely dispersed NaBaPO 4 :Eu 2+ phosphor is synthesized using a modified sol-gel method and studied to make a detailed energy chart of luminescence centers, including specific energy levels of surface sites. A nanosized (particles below 100 nm) YF 3 :Yb 3+ ,Er 3+ phosphor synthesized via hydrothermal technique is found to be useful for photodynamic therapy of abdominal cancer in couple with Radachlorin photosensitizer by generating active oxygen upon IR stimulation.