Synthesis And Characterization Of Organic Shell/CaS:Eu Core Fluorescent Material

Calcium sulfide doped with rare-earth Eu²⁺ ion (CaS:Eu) is a kind of excellent red phosphor, which can be well excited by the green and ultraviolet light and emit red light peaked at 650 nm with the 70 nm half-width. However, CaS:Eu is easy to react with water, oxygen and carbon dioxide in humidity air. Since that, the fluorescence intensities degradation of CaS:Eu is very speedy when it's exposed to the air, which restrict its application. In the other hand, CaS:Eu phosphor can not be dispersed well in the polymer. So it is necessary for CaS:Eu to be modified before use.Customarily, the method of modifying the phosphors is to coat appropriate protective layer on the surface, which is called as core-shell particles with phosphors as the core and coatings as the shell. Inorganic compounds are mainly reported as the surface coatings, especially the oxides with stable chemical properties, such as SiO₂ witch has good optical properties.Although CaS:Eu coated with SiO₂ has good properties against moist air, it is still not disperse very well in polymer. Basing on CaS:Eu phosphor have been applied in polymer, it is necessary for CaS:Eu phosphor to enhance waterproof and disperse stimulatory. In this thesis, core-shell (CaS:Eu@organic film) fluorescent materials were studied, and the details are as follow:1 Synthesis and Characterization of CaS:Eu@SA core-shell phosphorA layer of stearic acid was coated on the surface of CaS:Eu phosphor by a simple reaction in solution. The results of IR showed that stearic acid had been linked to the surface of CaS:Eu by chemical band. According to the results of particle size distribution, the best thickness of the shell is 1.67μm. XRD displayed that a small quantity of stearic acid didn't change the crystal structure of CaS:Eu. The fluorescence spectra illuminated that the stearic acid coating has no remarkable effects for their emission spectra except a little decrease of their FL intensities. But the water resistance of the CaS:Eu has been enhanced to great extent.2 Synthesis and Characterization of CaS:Eu@PS-PAA core-shell phosphorIn this paper, a layer of PS-b-PAA (polystyrene-block- poly(acrylic acid)) was coated on the surface of CaS:Eu phosphor by a copolymerization process in solution. IR and XRD indicated that a layer of PS-b-PAA indeed covered on the surface of CaS:Eu phosphor, acrylic acid reacted with metal ions which is on the surface of phosphor can result in the PS-b-PAA adhering better on the surface of phosphor. The PS-b-PAA shell almost has no effect to crystal structure and FL intensities of CaS:Eu. 3 Synthesis and Characterization of Eu-doped PS-b-PAASynthesized Eu (AA)₃ firstly and copolymerized Eu (AA)₃-ST later. XRD of the samples showed that Eu-doping lower copolymerization degree. The fluorescence spectra indicated that the Eu-doped copolymer can be excited effectively by ultraviolet light and blue light, and exhibit red performance.4 Synthesis and Characterization of CaS:Eu@Eu-PAA-PSCaS:Eu was hybrided with Eu-PAA-PS by copolymerization process in solution. The novel core-shell Inorganic-Organic hybrided fluorescent material is labeled as CaS:Eu@Eu-PAA-PS. The FL spectra displayed that CaS:Eu and Eu-PAA-PS didn't impact each other. Eu-PAA-PS enhanced the absorbance of ultraviolet light. In addition, the hybrided inorganic-organic fluorescent material could disperse in polymer well.