Research On Preparation And Performance Of Rare Earth Vanadate Nanomaterials

Due to the unique magnetic,catalytic and optical properties of rare-earth metalions based nanomaterials,they play an extremely important role in many fields,such as low-threshold lasers,bio-imaging contrast agents,TV picture tubes,mobile phone screens,white LEDs,fluorescent lamps,optoelectronic devices,etc.The rare earth metal ion-doped luminescent materials have attracted growing attentions due to their high fluorescence quantum yield,low toxicity,and harmlessness to the ecological environment.In this dissertation,a series of lanthanide metal ion-doped rare earth vanadate nanomaterials were synthesized by a simple and rapid microwave hydrothermal method.Their applications of as-prepared compounds in biological imaging and fluorescent printing has been emphatically explored for their characteristics of good water solubility,high fluorescence quantum yield,and low biological toxicity,etc.In the first chapter,the luminescence mechanism,research overview and application progress of rare-earth metal ions based fluorescent nanomaterials are introduced.Finally,the goals and significance of this study are also presented.In the second chapter,utilizing water as the solvent and polyacrylic acid?PAA?as the surfactant,high-quality Lu VO₄:Eu nanoparticles were synthesized by a microwave-assisted hydrothermal process.The conditions for synthesizing high-quality Lu VO₄:Eu nanoparticles were screened out by adjusting p H,temperature and the concentration of Eu³⁺ions.When the p H of the reaction solution wasgradually increased from 6 to 9,and then to 12,the corresponding fluorescence intensity gradually increased.At a reaction temperature of 180°C,Lu VO₄:Eu nanoparticles show a uniform and stable morphology,but they cannot maintain their morphology at low temperature.The concentration of luminescent ions is a very important factor to affect the fluorescence intensity of nanoparticles.It can be concluded that the Eu³⁺doping concentration 5 mol%should be the optimal concentration.The average size of as-prepared nanoparticles is about 165 nm.The aqueous solution of the nanoparticles shows fluorescence under an ultraviolet lamp.The as-prepared Lu VO₄:Eu nanoparticlespossessed good crystalline structure,high water-solubility and intense fluorescence emission.The aqueous solution of as-prepared nanoparticles was used as ink for fluorescenceanti-counterfeiting.In the third chapter,amino acid capped YVO₄:Eu nanoparticles were synthesized via a facile and green microwave-assisted hydrothermal method by using water as solvent and amino acid as a template agent.The as-prepared nanoparticles have good crystallinity,high water-dispersibility and small size?sub-50 nm?.Meanwhile,the effects of the amounts of amino acids on the structure and morphology of synthetic nanoparticles were also studied in detail.The synthetic approach is equally suitable for the syntheses of other rare earth vanadates.The YVO₄:Eu nanoparticles exhibit excellent luminescent property under the excitation of UV light.It has been successfully applied to the fabrication of luminescent devices.Amino acid-coated YVO₄:Eu nanoparticles were dispersed in polyethylene glycol via crosslinking-curing to obtain white composite models.These models have a certain toughness and can maintain a unique shape for a long time.YVO₄:Eu nanoparticles have good biocompatibility and good membrane permeability.YVO₄:Eu nanoparticles wereused as fluorescent probes to label mouse colon cancer cells?CT26 cells?.These results indicate that amino acid-encapsulated YVO₄:Eu nanoparticles have potential in cell detection and sensing as fluorescent probes.In the chapter four,the Gd VO₄:Eu nanoparticles have been synthesized via a microwave-assisted hydrothermal method.Meanwhile,the effects of theamounts of amino acids on the structure and morphology of synthetic nanoparticles were also studied in detail.A series of property measurements were performed on the samples,and various physical and chemical properties of Gd VO₄:Eu nanoparticles were studied in detail.In order to test the performance of Gd VO₄:Eu nanoparticles as bioprobes,we injected them into mouse colon cancer cells and tested the fluorescence imaging with different concentrations of Gd VO₄:Eu nanoparticle.The last chapter is the summary and perspectivesof the research project.This thesis illustrates the systematic syntheses of rare-earth vanadates nanomaterials and their applications in fluorescence imaging and other filds.