Synthesis of the aqueous soluble mesoporous silica functionalized luminescent La(OH)3:Pr core-shell nanospheres

La2O3:Pr3+ nanospheres (core-NSs) were successfully prepared by a urea-supported low-temperature thermal decomposition process. X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), Raman, UV-visible, and photoluminescence methods were applied for the characterization of the as-prepared silica surface functionalized luminescent core and La(OH)(3):Pr@SiO2@mSiO(2) (core/shell) NSs. XRD profile shows the reduction in diffraction peak intensities after silica layer growth over the core-NSs. TEM micrographs display the obvious difference in core and core-shell structure with an estimated grain size of about 56, and 180 nm of the core, and core-shell NSs, respectively. FTIR spectra exhibited the well-resolved IR peaks of the silica layer at a lower frequency range. Raman spectra show the prominent active vibrational modes at lower frequency regions. UV-visible spectrums exhibited that the band edge was significantly shifted to a higher wavelength after silica layer deposition over the luminescent core-NSs in both H2O and ethanol solvents. Absorption spectra revealed good aqueous dispersibility and colloidal performance in aqueous solvents. The optical band gap was calculated from the absorption spectra in both solvents. Pr3+-ion-doped La2O3 and silica functionalized core/shell NSs can be efficiently irradiated from the 443 nm (H-3(4) -> P-3(2)) excitation wavelength to emit multi-color sharp luminescence transitions in the visible region. The emission efficiency and colloidal dispersibility of the core-shell NSs may be useful tools in the photonic-based biomedical window.

Automated summary

La2O3:Pr3+ nanospheres were prepared by a urea-supported low-temperature thermal decomposition process. Characterization techniques such as XRD, FTIR, Raman, UV-visible, and photoluminescence were used to study the core and core-shell NSs. The results showed that the silica layer deposition over the core-NSs led to a reduction in diffraction peak intensities, a change in grain size, and a shift in the band edge. The core-shell NSs exhibited good aqueous dispersibility, colloidal performance, and multi-color luminescence transitions.