Preparation And Three-dimensional Display Applications Of Rare Earth Nanoparticles/PMMA Covalent-linking Nanocomposites

Three-dimensional?3D?perception of human is a complex cognitive process involving the eyes and the brain as a visual system.That the real-time volumetric data can be visualized in true 3D form has been a goal of display development efforts for years.A few clever systems have thus far been developed,such as virtual reality displays,holographic and stereoscopic display,relying on deceiving the visual system of human to think that it is seeing a two-dimensional scene in three dimensions.Although to a certain extent,meeting the needs to watch volumetric data in 3D form,these display technologies have many restrictions.Based on two-step,two-frequency?TSTF?upconversion,the true 3D display technology can display 3D objects in 3D spatial form.This technology allows the users to obverse 3D objects in all directions with naked eyes without these restrictions,such as the numbers and observation areas of observers.Organic-inorganic nanocomposites consisting of nanoparticles and polymers is a new kind of material,combining the advantages of both inorganic nanoparticles and polymer,exhibiting improved electrical,thermal optical properties.The incorporation of inorganic fluoride nanocrystals with high upconversion efficiency into polymer matrices is a good route to synthesize such upconversion luminescent polymer based nanocomposites which can be used as the 3D display medium.Polymethyl methacrylate?PMMA?,commonly known as plexiglass,is a good choice for matrices with good processing ability and high transparency in the visible region.The aggregation of particle is the main problem for polymer nanocomposites,which is due to the volume effects and specific surface area.Therefore,it is difficult to make nanoparticles monodisperse in the polymer matrix.The previous preparation methods,such as in situ polymerization,blending and so on,can not solve this problem well.To solve this problem,the nanoparticles was functionalized with unsaturated C=C bonds to link to the polymer chains via covalent bonds,making the inorganic nanoparticles disperse homogeneously and stably in the polymer nanocomposites.The main research contents are as follows:?1?In order to obtain Na YF₄ nanocrystals with high upconversion efficiency,monodisperse and uniform size,we respectively used solvothermal method by hand and high temperature thermal decomposition method by the machine?ANS01/02Automatic nanomaterials synthesizer?to prepare Na YF₄:20%Yb³⁺,2%Er³⁺and NaYF4:20%Yb³⁺,0.5%Tm³⁺.Oleic acid?OA?is the surface active agent,modifiying the unsaturated double bonds on the surface of the nanoparticles in one step.Firstly,X-ray diffraction,transmission electron microscopy,spectrometer and other test methods were used to characterize the morphology and optical properties of the nanocrystals.In order to copolymerize with polymer monomers,these nanoparticles were modified with unsaturated bonds.Meanwhile,fourier transform infrared?FTIR?spectrophotometer was used to recorded the surface properties of nanocrystals.The results show that this two kinds of nanoparticles are both below 20 nm in size with uniform morphology and high upconversion efficiency.The infrared absorption spectra showed that the nanocrystals surface was successfully modified with unsaturated group for the following copolymerization with polymer monomers.However,the crystalline phase of the nanoparticles synthesized by the solvothermal method is a mixture of cubic and hexagonal phases.Meanwhile,the crystalline phase of the nanoparticles synthesized by the high temperature thermal decomposition method is pure hexagonal phase.The upconversion luminescence properties of the pure hexagonal nanoparticles are superior to those of mixed phased nanoparticles.?2?Copolymerization of NaYF₄ nanoparticles and methyl-methacrylate let the upconversion nanoparticles link to the polymer chains via covalent bonds,making the inorganic nanoparticles disperse homogeneously and stably in the polymer nanocomposites.The nanoparticles functionalized with unsaturated C=C bonds were copolymerizedwithmethyl-methacrylatetosynthesizeNaYF4-PMMA covalent-linking nanocomposites with great transparency.Transmission electron microscopy was used to characterize the dispersion of nanocrystals in the polymer matrix.The results showed that nanocrystals had good dispersion in the matrix with no obvious agglomeration.Using these transparent Na YF₄-PMMA nanocomposites as display medium,3D structural upconversion luminescent images were generated via the computer-controlled 980 nm laser scanning.The emission colors can be easily controlled by doping or co-doping different upconversion nanoparticles without changing the luminescence properties of nanoparticles.The result presents the potential applications of polymer nanocomposites for 3D solid-state multicolor display.