Size-controlled La0.85Yb0.12Er0.03F3 up-conversion nanophosphors: co-precipitation synthesis using EDTA as chelating agent

In this research, uniform LaF3 nanoparticles have been successfully synthesized via co-precipitation route in which ethylenediaminetetraacetic acid (EDTA) was used as an effective size-controlled chelating agent. The appropriate analyses were carried out to characterize final nano-crystallites such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The results revealed that the nanoparticles were well-crystallized with hexagonal structure and were coated with an organic additive. From the scanning electron microscopy (SEM) micrographs, the spherical particles in the presence of EDTA were more uniform with higher detectable boundary phase. The dynamic light scattering (DLS) results showed that the mean diameter for samples with and without EDTA is 66.1 and 106 nm, respectively. Furthermore, from up-conversion luminescence (UCL) spectrum under excitation at 980 nm, the La0.85Yb0.12Er0.03F3 nanoparticles exhibit the bright orange emission photo-physically originated from separate transitions: 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 at 520, 538 and 658 nm, respectively. Consequently, as prepared LaF3:Yb,Er with relatively bright up-conversion luminescence can be a promising candidate for use as bio-labels.