Photochemical studies of monodispersed YPO4:Eu microspheres: The role of surface modification on structural and luminescence properties

Well-aqueous soluble, monodispersed, luminescent YPO4:Eu (core), YPO4:Eu@LaPO4 (core/shell) and YPO4:Eu@LaPO4@SiO2 (core/shell/Si) microspheres (MSs) were fabricated at low temperature with a facile synthesis process. TEM micrographs demonstrate the monodispersed, spherical shaped MSs were effectively covered with rough, porous silica surface, which is average grain size around 223 nm. Energy dispersive X-ray analysis and FTIR spectral studies verified the silica surface modification. High absorbance of silica modified core/shell/Si MSs in the ultraviolet region suggests the good solubility and colloidal stability in an aqueous environment. Photoluminescence intensity of the electric-dipole (D-5(0) -> F-7(2)) transition was dramatically decreased and magnetic-dipole (D-5(0) -> F-7(1)) transition was increased in core/shell MSs regardless core MSs, it could be due to the formation of the undoped LaPO4 shell surrounding the luminescent seed core-MSs. The formation of silica layer over the core/shell MSs not only increase the particle size but also improve the solubility character, however silica layer greatly quenched the luminescence intensity because of enhancement in multiphonon relaxation rate. Our finding suggests that monodispersed, spherical shaped luminescent MSs could be suitable materials for future use in photonic based bioapplications. (C) 2017 Elsevier B.V. All rights reserved.