Fluorescent Rare-Earth Nano-Particles: Synthesis And Application For Developing Fingerprint

Fluorescent rare-earth nanomaterials are defined as the particles with the sizes between 1 and 100 nm containing rare-earth ions. In the fields of basic research and technological application, much attention has been given to yttrium vanadate (YVO4) and lanthanum phosphates (LaPO4) host materials, which exhibit excellent fluorescent properties. Compared with traditional organic fluorescent dyes, fluorescent rare-earth nanomaterials have many advantages, such as low toxicity,no blinking behavior,high chemical stability,good biological compatibility and long fluorescent life, that make them potentially suitable for biolabeling applications. At present, the fluorescent rare-earth nanomaterials synthesized by conventional method, such as high temperature solid state method,sol-gel method,precipitation method and hydrothermal method, are powders with irregular morphology and wide particle size distribution and so cannot meet the requirement of biolabeling materials. In this thesis, a series of fluorescent rare-earth nanoparticles (NPs) with well suspension stability were synthesized in aqueous-phase. The preparation routes,modifiers,structure and fluorescent properties and application in developing fingerprint of fluorescent rare-earth NPs are also studied. The main results of the thesis are summarized as follows:1. YVO4:Eu were synthesized in aqueous-phase using rare-earth nitrate and sodium metavanadate (NaVO3) as raw material and citric acid as complexing agent. The effects of pH values,reaction time,reaction temperature and the molar ratio of Y/Eu on particle size,morphology,lattice parameter and fluorescent intensity were studied by XRD,TEM and fluorescence spectra. The results indicate that the synthesized YVO4:Eu aqueous colloids with particle size of about 10 nm are of tetragonal system and can be dispersed well in water, in which the Y0.7VO4:Eu0.3 synthesized at the conditions of pH= 9.0, t=1 h and T=60℃, has the highest fluorescent intensity at the emission peak of 619 nm. Under UV irradiation, the fingerprint details on the surface of smooth objects can be clearly developed in red color with modified Y0.7VO4:Eu0.3 aqueous colloids.2. The LaPO4:Ce,Tb aqueous colloids with homogeneous and smaller particle sizes were synthesized by hydrolysis of an aqueous mixture of sodium tripolyphosphate (Na5P3O10) and rare-earth nitrate. The XRD,TEM and fluorescence spectra results indicate that the La0.65PO4:Ce0.25,Tb0.10 aqueous colloids with particle size of about 8.3 nm synthesized at the conditions of pH=9.0, t=3h and T=90℃, have the highest fluorescent intensity of which the quantum yield can be up to 50.05%. The La0.65PO4:Ce0.25,Tb0.10 aqueous colloids modified with thioglycolic acid (TGA) can develop the clear and full fingerprint with bright green light.3. Some simulated amino acid and simulated grease solution were prepared according to the composition consisting of fingerprint substance, and their influences on several fluorescent nanomaterials and modifiers were evaluated. The results indicate that fluorescent nanomaterials with carboxyl or mercapto functional groups can be connected with fingerprint substance and develop the fingerprint clearly.