Controllable Synthesis and Size-Dependent Luminescent Properties of YVO4:Eu3+ Nanospheres and Microspheres

Uniform, monodispersed, and size-controllable YVO4:Eu3+ nano- and microspheres ranging of 20-1200 nm in diameter were successfully synthesized under the solvothermal condition with N,N-dimethylformamide as the solvent, poly(vinyl pyrrolidone) (PVP) and cetyltrimethyl ammonium bromide (CTAB) as surfactants, meanwhile, introducing HCl acid in the reaction. They were characterized by various techniques, including field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray power diffraction (XRD), and Fourier transform infrared (FTIR) spectra. The results indicate that the assistant of PVP played an important role in the formation of uniform and monodispersed YVO4: Eu3+ spheres, which effectively prevented aggregation of crystallites. The amount of acid can adjust particle size, while the coassistant of CTAB is helpful of forming spherelike particles. A possible formation mechanism of YVO4:Eu(3+)spheres was proposed. Furthermore, size-dependent luminescent properties were studied. It is interesting to observe that the excitation bands originating from VO43- groups became narrow on the red side with the decreasing particle size, which is attributed to the size confinement effect to energy transfer. As a consequence, the intensity ratio of D-5(0)-F-7(1) to D-5(1)-F-7(3) increased and the initial population ratio of D-5(0)-D-5(1) increased. A detailed model was proposed to explain the size-dependent photoluminescence.