Luminescence properties of Sm3+ doped YPO4: Effect of solvent, heat-treatment, Ca2+/W6+-co-doping and its hyperthermia application

Sm3+ doped YPO4 spherical nanoparticles are prepared by wet chemical route. Pure YPO4 shows the tetragonal phase, which is stable up to 900 degrees C, whereas pure SmPO4 shows the phase transition from hexagonal to monoclinic when heated above 800 degrees C. The (2-10 at.%) Sm3+ doped YPO4 shows the mixture of phases of tetragonal and hexagonal, which transform to the tetragonal phase above 800 degrees C. Infra-red study could distinguish confined water in the pore of hexagonal phase from water present on the surface of particles. Luminescence intensities of Sm3+ at 564, 601 and 645 nm are weak in case of as-prepared samples because of high non-radiative rate arising from the H2O molecules present in pores of hexagonal lattice. The intensities increase for samples heated up to 900 degrees C because of increase of extent of radiative rate. Luminescence lifetime increases with increase of heat-treatment up to 900 degrees C. When solvent of as-prepared sample was changed from the H2O to D2O, 5 times enhancement in luminescence intensity is observed, which can be ascribed to the lower vibration energy of D-O over H-O, which is near to Sm3+. When Y3+ and P5+ ions are substituted by Ca3+ and W3+ up to 3 at.%, there is an enhancement of luminescence. In order to use them as bio-labeling in drug delivery for hyperthermia applications, hybrid of Fe3O4@YPO4:7Sm is prepared and heating up to 45 degrees C is observed under AC magnetic field. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4773443]