Doctoral defence: Sanu Bifal Maji „Synthesis and luminescence investigation of nanoparticles doped with Pr³⁺ ions in selected fluoride and phosphate hosts“

On 13 November 2025 at 12.15 Sanu Bifal Maji will defend his doctoral thesis „Synthesis and luminescence investigation of nanoparticles doped with Pr³⁺ ions in selected fluoride and phosphate hosts“.

Juhendajad:

Prof. Marco Kirm, Institute Physics, University of Tartu

Dr. Alexander Vanetsev, Institute Physics, University of Tartu

Oponent:

Prof. Anatolijs Šarakovskis, Institute of Solid State Physics University of Latvia, Latvia

Summary

Light has fascinated humanity for centuries, not only for its beauty but also for its practical value in illumination and healing. Recent research shows that specific wavelengths can be used against treatment of tumors. My PhD research develops and investigates wide bandgap fluoride and phosphate nanoparticles doped with praseodymium (Pr³⁺) ions. In my work I synthesized nanoparticles by hydrothermal and solvothermal synthesis methods (BaLuF₅, BaGdF₅, LuPO₄, BaLu₂F₈–BaLuF₅). I investigated their luminescence properties at synchrotron facilities (MAX IV, Sweden; PETRA III, Germany) using time-resolved spectroscopy across a wide temperature range.
These nanoparticles emit either ultraviolet radiation in the 200–280 nm UV-C range or visible light when excited by ionizing radiation such as X-rays or energetic particles. A wide variation in the emission range arises from the unique energy-level scheme of Pr³⁺, spanning both UV-C and visible regions depending on the crystal field strength of the host material. Emission in the UV-C region overlaps with DNA absorption, enabling cancer cell destruction, while visible emissions from these nanoparticles activate photosensitizers molecules for the photodynamic therapy. By fine-tuning of nanoparticles’ structure and composition, simultaneous emission is achieved for UV-C and visible regions, enabling combined therapies. I also studied how temperature-driven structural changes influence luminescence. Thermal annealing reduced short-range disorder, increased nanoparticle size, and enhanced emission intensity up to four times.
This research advances the development of multifunctional Pr³⁺ based light emitters for tumor therapies, where nanoparticles could be transported to locations of tumors and be activated by external radiation, working precisely without invasive surgery or severe side effects.