Study On Preparation And Properties Of Temperature Sensitive Fluorescent Composites Based On Rare Earth Oxides

Rare earth oxides have excellent performance and broad application prospects,their research and development have aroused extensive attention. They have beenwidely used in laser materials, phosphors and catalysts. As fluorescent substance, rareearth oxides have strong fluorescence because of more energy level transitions. In thisstudy, based on the fluorescent properties of rare earth oxides, we chose differentmaterials which can play a role in fluorescence quenching with rare earth oxides, andprepared different composites. Then, the composites were calcined from a lowtemperature, in the calcination, the fluorescence intensity of composites graduallyincreased with the increasing of calcination temperature. Within a certain temperaturerange, the fluorescence intensity of the composites responsed to temperature,therefore, the composites can be used as temperature-sensitive material. In addition, inorder to effectively control the morphology of rare earth oxides, we chose thefluorescence quencher purposely as a template, which can be easily removed and withone-dimensional nano-structure. By using of surfactant and cross-linking agent, rareearth oxides were coated on the surface of these templates, then the composites werecalcined at high temperature to remove the template, thereby to obtain a rare earthoxides with a one-dimensional nano-structure.The study is divided into three parts:First, rod-shaped La2O3:Eu3+nanocrystalline has been successfully synthesizedby a facile solvothermal method using carbon nanotubes (CNTs) as removabletemplates. The mass loss and thermal stability of the composites were characterizedby TGA curves. The XRD pattern showed the highly crystalline of samples and noother phase. The morphology of the samples was also characterized by Scanningelectron microscopy and transmission electron microscopy. Fluorescencecharacteristics of composites were analyzed by fluorescence spectroscopy. In addition,when the CNTs/La2O3:Eu3+composites were calcined at different temperatures, wediscovered that the composites show an increase in the fluorescent intensities withincreasing calcination temperature, showing a significant temperature-sensitivecharacteristic. In the experiment, we found that carbon nanotubes have a strong fluorescence quenching, we took advantage of such effect and prepared thetemperature-sensitive fluorescent composite materials. The composites have potentialapplications can be used for high-temperature warning, temperature-sensitive sensors,monitors, etc.Second，we used fluorescence quenching effect of polypyrrole and combinedwith rare earth europium oxide, then prepared polypyrrole/europium oxidetemperature-sensitive fluorescent composites. The composites show the fluorescenceintensity gradually increased with the increasing of calcination temperature. Thefluorescence intensity of the composites responsed to the calcination temperature,showing a significant temperature-sensitive characteristic, therefore, the compositescan be used as temperature-sensitive material. The mass loss and thermal stability ofthe composites were characterized by TGA curves. Further, in order to be consistentwith the previous chapter, we have prepared polypyrrole into nanowire purposely,then used it as a template to prepare rod-shaped europium oxide. Their morphologywas characterized by scanning electron microscopy. This can be said to have foundanother new template to prepare nanostructure rare earth oxides.Third, in this chapter experiment, we also used fluorescence quenching effect ofpolyaniline and combined with rare earth europium oxide, then preparedpolyaniline/europium oxide temperature-sensitive fluorescent composites. Thefluorescence intensity of the composites responsed to the calcination temperature,showing a significant temperature-sensitive characteristic, therefore, the compositescan be used as temperature-sensitive material. The mass loss and thermal stability ofthe composites were characterized by TGA curves. Here, we used polyaniline as atemplate to prepare rod-shaped europium oxide, their morphology were characterizedby scanning electron microscopy.