Highly biocompatible, monodispersed and mesoporous La(OH):Eu@mSiO core-shell nanospheres: Synthesis and luminescent properties.

Monodispersed La(OH):Eu nanospheres(core-NSs) were synthesized by urea-based homogeneous co-precipitation process, where mesoporous silica layer was coated over the surface of luminescent La(OH):Eu core-NSs. The XRD data exhibit the high crystalline, single hexagonal-shaped La(OH):Eu core and silica modified La(OH):Eu@mSiO (core-shell) NSs. Monodispersibility, spherical shaped, high surface area and mesoporosity were identified by TEM analysis and were further confirmed by BET analysis. The as-synthesized samples are highly soluble in aqueous media at ambient conditions. Spectroscopic analyses were also carried out to examine the impact of surface modification on structural, surface chemistry, optical and luminescence behavior of the as-designed silica coated core-shell NSs. The emission spectral study revealed that the luminescence intensity of magnetic-dipole transition (590 nm, D → F) is dominant with respect to electric-dipole (614 nm, D → F) transition. The high crystallinity of the hydroxide products supports the existence of good photoluminescence intensity, a good indication for their future use in detection of biomacromolecules through hypersensitive emission (614 nm, D → F) transition. Excellent biocompatibility, cell viability and good luminescence properties suggested that the as-prepared core-shell NSs are an ideal candidate for luminescence biolabeling/bioimaging and as an optical bio-probe.