The Preparation Of Nanometer Silver Doped With Rare Earth Fluorescent Material And The Fluorescence Enhancement Effect Research

Spherical silver nanoparticles, triangular silver, silver nanowires and other metal nanometer structure were prepared in this article. The influence of nano silver particles on the luminescent properties of SiO2:Eu2+silicon-based films、SiO2:Tb3+phosphor、Sr2SiO4:Eu2+nanorod, silver nanowires on luminescent properties of SiO2:Eu2+nanoparticles and other rare-earth doped phosphor materials were studied. While the fluorescence enhanced and the enhancing mechanism were emphatically analyzed and discussed. In addition, this article did part of work on preparation of rare-earth doped phosphor materials and valence change for the variable rare earths. The mechanism of Eu3+to Eu2+in the SiO2matrix, preparation of Sr2SiO4nanotubes and, Sr2SiO4Clustered nanorods via sol-gel method and pechini sol-gel method, and the luminescent properties and energy transfer process of Ce3+, Tb3+in Sr2SiO4matrix were discussed.(1) The successful combination of nano silver sol with nano rare-earth materials preparation overcomes the difficulties in Theoretically Combining nano silver sol with rare-earth solid materials. Spherical silver nanoparticles were doped in SiO2precursor solution to prepare nano SiO2:Tb3+-Ag phosphor. Results showed that the intensity of Tb3+fluorescence increased, the lifetime of Tb3+fluorescence reduced and ultraviolet absorption increased. In addition, Ag doping enhanced the fluorescence intensity of Tb3+by35%at543nm. The above phenomena were attributed to the localized field enhancement effect by Localized Surface Plasmon Resonance from Ag nanoparticles in the matrix, resulting in ultraviolet absorption enhancement. Additionally, the fluorescence enhancement was originated from the increased radiative decay rates of Tb3+after doping of Ag nanoparticles.(2)Innovatively combining the preparation of nano silver with the preparation of rare earth inorganic materials to prepare nano SiO2materials co-doped with Eu3+and Ag nanowires via one-step revivification method. In the process of preparation, the Eu(NO3)3and AgNO3were added into the TEOS precursor solution, and after reduction the Ag nanoparticles disperse homogeneously into the Eu2+codoped SiO2phosphor. This method overcomes the problem of uniformity when Ag nanoparticles were directly doped into SiO2:Eu2+rare-earth solid materials.The as-prepared Ag nanowires had an average diameter of12.50nm, their length range from20nm to350nm, and the aspect ratio was.30. When the doping concentration of nano silver was0.1%, the sample showed the highest fluorescence intensity, the increased multiple was16times. The doping of nano silver enhanced the absorption in range from230nm to350nm, reduced the fluorescence lifetime and caused obvious red-shift of the emission peaks. The fluorescence enhancement mainly originated from the localized field enhancement and radiative decay rate increase induced by silver nanowires. The enhancement effect of Silver nanowires for Eu2+was obviously stronger than the enhancement effect of spherical silver nanoparticles for Tb3+. The phenomena were related to the overlap degree of resonance absorption peak at420nm and Eu2+emission peak, metal nanoparticles, fluorescent center distance and other factors, namely the comprehensive action of localized field enhancement and radiative decay rates increase.In addition, fluorescence of Tb3+and Eu2+belonged to two different energy level transition processes. Tb3+obeyed4f-4f energy level transition, which was less affected by the external field. While Eu2+obeyed4f65d1to4F7transition. As electrons in5d layer exposed to the outside, not shielded by other electronic shells, the transition was strong influenced by the external field. Due to the presence of silver nanowires, Localized surface plasmon resonance was generated by the surface of nano silver or silver nanowire in external electromagnetic field. The localized electromagnetic field was increased, and changed the strength of the electromagnetic field around Eu2+in SiO2matrix, which improved the excitation efficiency of fluorescent molecular and greatly enhanced the fluorescence emission intensity.(3) Amorphous SiO2:Eu2+phosphor materials were prepared via sol-gel method to investigate the conversion mechanism of Eu3+to Eu2+in the SiO2matrix. When Al3+took place of Si4+after entering the network structure of SiO2, aluminum-oxide tetrahedron with a unit negative charge formed, which impelled the conversion from Eu3+ions to Eu2+ions. The system exhibits strong blue emission under different temperatures, and at the same annealing temperature, SiO2codoped with boron and aluminium showed stronger luminescent properties than the one doped with aluminium. The results indicated that the doped of B ions was help for the Eu3+ions to Eu2+ions change and stabilization, contributing to the blue emission. Spherical silver nanoparticles were spin-coating on the surface of silicon-based films. The silver nano-particles increased the localized electromagnetic field around. Eu2+, leading to the improvement of fluorescent molecular excitation efficiency, and the fluorescence intensity enhancement can be about1.1times.(4) With Sr,SiO4as the matrix for LED, Eu2+、Ce3+、Tb3+rare earth elements as activators, the sample was prepared to explore the influence of different preparation methods on sample morphology and crystal type. The effects of other factors, such as dopant concentration and preparation conditions, on the luminescent properties of the samples were investigated as well. In addition, some preliminary exploration on the fluorescence enhancement effect of nano silver on Sr2SiO4:Eu2+were carried out and an enhancement phenomenon had been observed.①Sr2SiO4:Eu2+nanotubes were prepared by sol gel method. In the prepare process, nano SiO2was used as the source of silicon, in the fluxing action of boric acid, monoclinic α’-Sr2SiO4was obtained. Eu2+ions occupied the crystallographic sites of Sr(Ⅰ), emits blue fluorescence at488nm. And when the annealing temperature was1350℃and Eu concentration was0.5%, the sample had the strongest blue emission intensity.②Cluster nanorods of Sr2SiO4:Eu2+and Sr2SiO4:Eu2+,Ag were prepared via pechini sol-gel method with Sr2SiO4as matrix and SiO2as silicon source. And the diameters of the nanorods was about45nm.and the length of the nanorods were range from0.5um to1.3um. In the as-prepared samples, Eu2+replaced the Sr(Ⅰ) site and Sr(II) site, and showed blue and yellow emission at485nm and550nm, respectively. The fluorescence intensity of sample doped with Ag was obviously higher than the one undoped, and the enhancement was2.5times.③Luminescence properties of Ce3+and Tb3+single doped Sr2SiO4and process of energy transfer of Ce3+and Tb3+co-doped Sr2SiO4. Sr2SiO4:Ce3+, Sr2SiO4:Tb3+and Sr,SiO4:Tb3+, Ce3+nano phosphor materials were prepared by Sol-gel method. Sr2SiO4:Ce3+showed blue emission of465nm under265nm excitation. Sr2SiO4:Tb3+emitted weak blue light (400nm～450nm) and strong green (480nm～600nm) under the ultraviolet light of280nm,respectively corresponding to the5D3�'7Fj(j=3,4,5,6) and5D4�'7Fj(j=3,4,5.6) transition of Tb3+. The Sensitization of Ce3+to Tb3+was observed in the Ce3+, Tb3+co-doped Sr2SiO4. When Ce3+was excited to5d state from ground state of2F7/2and2F5/2, green emission located in545nm were emit to increase the emission peak at545nm, which corresponding to5D4�'7F5of Tb3+. The energy transfer from Ce3+to Tb3+was conformed.