Synthesis And Luminescent Properties Of PMMA Rare Earth Nanocomposites

With the development of science and technology,unitary nature of the materials can not meet the demands,and it is urgent to develop new materials.Polymer-based rare earth luminescent nanocomposites combine the advantages of both polymers?good processability and good mechanical properties?and rare earth luminescent materials?extremely sharp emission bands and high luminescence efficiency?and thus have attracted considerable attention.In this thesis,two series of monodisperse rare earth/silica luminescent nanospheres with different sizes were prepared and characterized.Then taking the luminescent nanospheres as functional component,four kinds of polymer-based rare earth luminescent nanocomposites were prepared by solution mixing method and their luminescent and thermal properties were also investigated.The main works of the present thesis are listed as follows:Two series of monodisperse luminescent nanospheres containing covalently bonded Eu³⁺(Tb³⁺)complexes on silica nanospheres with different sizes have been synthesized.The resulted luminescent nanospheres were characterized by FT-IR,TEM,UV-Vis,fluorescence spectroscopy,inductively coupled plasma spectroscopy and fluorescence lifetime.The results showed that the obtained nanoparticles have homogenous spherical shapes and transmission electron microscopy?TEM?investigations confirm the nanoparticles with average diameters of 40,60,and 93 nm,separately.Upon excitation at the maximum absorption of ligands,the resultant nanocomposites exhibit high fluorescence intensity and color purity in the visible region.Compared with the pure complex,the nanocomposites could emit dramatically stronger luminescence with much lower lanthanide ion content.Meanwhile,the influence of the size of nanomaterials on luminescent properties is also investigated.The results show that the loading amount of lanthanide complexes,the emission intensity and the color purity of the resultant nanomaterials increase with a decrease of nanosize.The fluorescence lifetimes of the nanocomposites are longer than that of the pure complex.However,the size of nanomaterials has little effect on the fluorescence lifetimes.A series of PMMA/SiO₂@TMA-RE nanocomposites were prepared from the monodisperse luminescent nanospheres with average diameter of 40 nm and polymethyl methacrylate as matrix.The nanocomposites were characterized by a combination of transmission electron microscopy,ultraviolet spectroscopy,fluorescence spectroscopy,TGA and DSC.Morphological examination of the nanocomposites revealed that the nanospheres were dispersed well in the matrix when the content of the luminescent nanospheres was less than 10%and was obvious agglomeration when the content was more than 20%.The nanocomposites had good transparency in the visible light range.The results of fluorescence spectroscopy showed that the fluorescence intensity of the nanocomposites increased with an increase of the content of silica nanospheres and the fluorescence intensity of PMMA/SiO₂@TMA-RE nanocomposites was higher than that of the luminescent nanospheres when the content of nanospheres was more than 10%.The fluorescence lifetimeanalysisresultsshowedthatthefluorescencelifetimeof PMMA/SiO₂@TMA-RE nanocomposites was longer than the luminescent nanospheres.Four kinds of polymer-based rear earth nanocomposites were prepared using PMMA,PS,PVC,PA₆ as matrix,separately.The fluorescent spectra of the nanocomposites indicated that the PVC/SiO₂@TMA-RE,PMMA/SiO₂@TMA-RE and PS/SiO₂@TMA-RE nanocomposites emit dramatically stronger luminescence than luminescent nanospheres and the PA6/SiO₂@TMA-RE emit weaker luminescence than luminescent nanospheres.This demonstrated that the polymer matrix had an effect on the fluorescence properties of the nanocomposite.