Concentration-induced morphological changes of biocompatible La${}^{3+}$, Yb${}^{3+}$, Er${}^{3+}$ tri-doped NaYF${}_4$ compounds

The upconversion (UC) materials possess luminescence and magnetic properties that attempt greater significance in detecting cancer cells. This work targets the effects of doping (10-30%) La${}^{3+}$ into NaYF${}_4$:Yb${}^{3+}$, Er${}^{3+}$ compounds using the hydrothermal technique with trisodium citrate as a stabilisation and capping agent. X-ray diffraction pattern (XRD) confirmed the crystal phases of La${}^{3+}$-doped (α + β) NaYF${}_4$:Yb${}^{3+}$, Er${}^{3+}$ compounds. The Williamson-Hall equation calculated the crystallite size and lattice strain of the synthesised particles. The morphological studies depicted the growth of the particles from hexagonal plates to rods on doping La${}^{3+}$ from 10 to 30% doping concentrations. The sample NaYF${}_4$:Yb${}^{3+}$, Er${}^{3+}$, 20% La${}^{3+}$ has shown maximum UC red emission and green emission intensity at 976 and 795 nm excitation, respectively, which makes the material eligible for bio-imaging application. The entire sample displayed paramagnetic properties. The cytotoxicity test on Vero cell lines assessed the viability of the prepared samples.