Spectral-kinetic properties of LaF$_3$ nanoparticles doped with Ce$^{3+}$ and Sm$^{3+}$ ions after microwave treatment and in core-shell structure

Crystalline LaF$_3$:Sm$^{3+}$ and LaF$_3$:Ce$^{3+}$ nanoparticles were fabricated via a co-precipitation method. The obtained nanoparticles were 15–20 nm and had good crystallinity. Spectral-kinetic properties of crystalline LaF$_3$ nanoparticles activated with 5 % Sm$^{3+}$ and 12 % Ce$^{3+}$ ions were studied. Various duration of the microwave treatment as well as core-shell structure were studied as possible ways to control quenching in the nanoparticles. In case of the LaF$_3$:Sm$^{3+}$ nanoparticles, the additional microwave treatment increased the average luminescence lifetime by 6 % and addition of the LaF$_3$ shell increased it by 18 %. In case of the LaF$_3$:Ce$^{3+}$ sample, microwave treatment increased the average lifetime by up to 20 %. The observed effects of varying the synthetic conditions and composite core-shell structure on luminescence properties of nanoparticles provide a means to manage the energy loss in the nanoparticles due to the quenching factors.