Synthesis And Characterization Of CaMoO₄Nanoparticles Prepared By Microwave Method

Rare-earth supported upconversion luminescence nanomaterials became a hot spot of many field and interdisciplinary research due to the strong photo-stability, narrow emission spectrum, long fluorescence lifetime, and it can be excited by continuously near-infrared. And more and more attention have been paid to upconversion nanoparticles in current years as their promising applications in optical fibers, display devices, bioimaging, drug delivery and solar cells. It is also spreading to other new technology areas. Microwave-assisted method is newly developing in recent years, which has the characteristics of fast synthetic speed, simple operation, high efficiency, energy conservation, time-saving, pollution-free and synthesis of high crystallinity, small size, uniform distribution nanoparticels in a limited time. Microwave dielectric constant and absorbing characteristics of metal molybdate are very conducive to create complex geometric structure by using microwave method, so this work we use this method to synthesize calcium molybdate upconversion material.Microscopic morphology, nanostructure and luminescence properties of the samples were investigated by scanning electron microscopy, transmission electron microscope, X-ray powder diffractions and fluorescence spectroscopy. Different factors (sintering temperature, pH, microwave time and microwave dielectric) that affect luminescent properties have been discussed. Green upconversion luminescence of CaMoO4:Er3+/Yb3+nanoparticles have been successfully synthetised by microwave-assisted method. The emission band of520-540nm was assigned to the transition2H11/2â†'4I15/2, and the emission band of540-570nm in the green region was assigned to the transition4S3/2â†'4I15/2.When the parameters of microwave time (9min), microwave dielectric (ethylene glycol) and sintering temperature (800℃) were fixed, we found when pH was3, fluorescence intensity was strongest. When the parameters of sintering temperature (800℃), pH=7and microwave dielectric (ethylene glycol) were fixed, we found when microwave time was9min, fluorescence intensity was strongest. When the parameters of microwave time (9min), pH=7and microwave dielectric (ethylene glycol) were fixed, we found when sintering temperature was800℃, fluorescence intensity was strongest. When the parameters of microwave time (9min), pH=7and sintering temperature (800℃) were fixed, we found when microwave dielectric was oleic acid, fluorescence intensity was strongest. White light emission of calcium molybdate upconversion luminescent nanoparticles was successfully prepared, when luminescent center is Ho""+, Tm3+ ions, Yb3+is the sensitized ion and the doping ratio of Ho3+/Tm3+Yb3+is0.8:0.2:15, respectively.