Synthesis and luminescence properties of highly uniform SiO2@LaPO4:Eu3+ core–shell phosphors

• SiO2@LaPO4:Eu3+ phosphors were synthesized by a wet-chemical method.
• The pH value plays an important role in the formation of core shell-structured particles.
• The SiO2@LaPO4:Eu3+ phosphors show strong orange–red luminescence.
• This synthesis route can lower the cost of precious phosphors.

SiO2@LaPO4:Eu3+ core–shell phosphors have been successfully synthesized by a one-step and economical wet-chemical route at low temperature. The as-obtained products were characterized by means of photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS). The SEM, EDS and XPS analysis indicate that SiO2@LaPO4:Eu3+ core–shell phosphors can only be synthesized in a pH range of 8–11 and the possible mechanism has been proposed. The XRD results demonstrate that the structure of LaPO4:Eu3+ layers is transferred into monoclinic phase from hexagonal phase after annealing at 800 °C for 2 h. The SiO2@LaPO4:Eu3+ phosphors show strong orange–red luminescence under ultraviolet excitation. The relative emission intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles, and the optimum concentration for Eu3+ was determined to be 5 mol% of La3+ in SiO2@LaPO4 phosphors.

(a) TEM image of SiO2@LaPO4:Eu3+: the left-upper insert is selected area electron diffraction (SAED) pattern, and (b) a typical HRTEM image.Figure optionsDownload as PowerPoint slide