Mesoporous multi-silica layer-coated Y2O3:Eu core-shell nanoparticles: Synthesis, luminescent properties and cytotoxicity evaluation.

Mesoporous multi-layered silica-coated luminescent Y2O3:Eu nanoparticles (NPs) were prepared by a urea-based decomposition process, and their surfaces were gradually modified with nanoporous and mesoporous silica layers using modified sol-gel methods. The synthesized luminescent core-shell NPs were characterized thoroughly to investigate their structural, morphological, thermal, optical, photo luminescent properties and their surface chemistry. The morphology of the core NPs were nearly spherical in shape and were nano-sized grains. The observed luminescent efficiency of the mesoporous multi-layered silica-coated luminescent core NPs was gradually reduced because of bond formation between the Y2O3:Eu core and the amorphous silica shell via YOSiOH bridges on the surface of the NPs; the bonds suppressed the non-radiative transition pathways. Biocompatibility tests on Human breast cancer cells using the 3­(4,5­Dimethylthiazol­2­yl)­2,5­diphenyltetrazolium bromide and lactate dehydrogenase assays indicated that the core-shell NPs were non-toxic even at high concentrations. The mesoporous SiO2 layer played a key role in perfecting the solubility, biocompatibility, and non-toxicity of the NPs. The zeta potential, surface chemistry (Fourier transform infrared spectroscopy), and optical absorption spectral analyses revealed the high hydrophilicity of the as-prepared core-shell NPs because of the active surface-functionalized silanol (SiOH) groups, which could potentially offer many exciting opportunities in photonic-based biomedical applications.

Highly biocompatible, monodispersed and mesoporous La(OH)3:Eu@mSiO2 core-shell nanospheres: Synthesis and luminescent properties.

Monodispersed La(OH)3: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)3:Eu core-NSs. The XRD data exhibit the high crystalline, single hexagonal-shaped La(OH)3:Eu core and silica modified La(OH)3:Eu@mSiO2 (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, 5D0 → 7F1) is dominant with respect to electric-dipole (614 nm, 5D0 → 7F2) 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, 5D0 → 7F2) 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.