ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

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

Vadim V. Bakhmetyev, Anastasia M. Dorokhina, Mariia V. Keskinova, Segrey V. Mjakin, Anna B. Vlasenko, Lev A. Lebedev, Vitalii V. Malygin, and Maxim M. Sychov

Department of Theory of Materials Science, Saint-Petersburg State Institute of Technology (Technical University), St Petersburg, Russia

E-mail: vadim_bakhmetyev@mail.ru

Received: 9 April 2019  Accepted: 13 August 2019

Abstract:

Finely dispersed NaBaPO₄:Eu²⁺, NaGdF₄:Eu³⁺, BaGdF₅:Eu³⁺, GdF₃:Yb³⁺, Er³⁺ and YF₃:Yb³⁺, Er³⁺ phosphors are synthesized using a sol–gel procedure and hydrothermal method. A process is developed for obtaining NaBaPO₄:Eu²⁺ 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 Eu²⁺ ions located in NaBaPO₄ lattice sites with coordination numbers 10 and 12, these phosphors are found to contain two more types of luminescence centers supposedly corresponding to Eu²⁺ ions in the same positions locating on the phosphor particle surface. According to the obtained data, the energy levels of luminescence centers in the NaBaPO₄:Eu²⁺ phosphor are summarized in a chart. NaGdF₄:Eu³⁺ phosphor is shown to be mostly appropriate for X-ray stimulated photodynamic therapy (PDT), while GdF₃:Yb³⁺, Er³⁺ phosphor is promising for IR-activated PDT. The efficiency of 980 nm IR laser-induced generation of active oxygen by a medicine involving the YF₃:Yb³⁺, Er³⁺ phosphor, and Radachlorin photosensitizer is studied.

Graphic Abstract:

A finely dispersed NaBaPO₄:Eu²⁺ 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) YF₃:Yb³⁺,Er³⁺ 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.

Keywords: Nanosized phosphors; Sol–gel method; Hydrothermal synthesis; Mixed phosphates; Fluorides; Photodynamic therapy; Active oxygen

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-019-00904-9

Chemical Papers 74 (3) 787–797 (2020)