Fabrication And Luminescent Properties Of NaGdF₄:Eu³⁺ Nanowires

Nanomaterials were the base of the application of nanotechnology. Low-dimensional nanostructured materials were the perfect models in the study of the essential physical properties of nanomaterials. In this thesis, Organic-inorganic nano-composite materials were selected as the objects for study. This class of materials have received extensive attention, I they can not only play a crucial role in important future optoelectronic devices, biochemical and chemical sensors, but also can be used to enrich our understanding of basic quantum mechanics.Electrospinning is a simple, versatile, and useful technique for fabricating nanofibers that are exceptionally long in length, uniform in diameter from a rich variety of functional materials. This technique have been selected to prepare the Organic-inorganic nano-composite fibers in this thesis. Dependence of the optical properties on the nanostructure, shape and size was researched.The main results are as follows:(1) We composed the Eu³⁺ doped NaGdF₄ nanocrystal with different crystal phase used a polyol method. we characterized the sample by powder X-ray diffraction (XRD) patterns, scanning electron microscopy(SEM) images and fluorescence spectra. The result indicate : we composed the Eu³⁺ doped NaGdF₄ nanocrystal with cubic and hexagonal crystal phase and size was about 20 to 30 nanometers;in cubic phase and hexagonal phase, with the Eu³⁺ ion doping concentration increase (1% 10%), the 5D0 to 7F1 transition of Eu³⁺increased monotonously ,but 5D0 to 7F1 transition have no law . we analysed the reason was the sample was not pure phase then cause the symmetry around Eu³⁺ changed .We also found out before 10 percent of Eu³⁺ ion doping there is no concentration quenching ,this is very different with the oxide .(2) By changing the ratio of PVP and NaGdF₄ , the calcination temperature, we synthesised of Eu³⁺ doped NaGdF₄ nanowires and studied the luminescent properties. This is the first time present the fluoride nanowires through the electrospinning method. The results showed that: we have synthesized the cubic phase NaGdF₄ nanowires and 100 300nm in size; XRD showed that the different calcination temperature, the ratio of PVP and NaGdF₄ for the formation of nanowires is important , we also got the best conditions: the ratio of PVP and NaGdF₄ was 2:1, calcination temperature was 600℃;The fluorescence spectra result indicate,the increase of the radiative electronic transition rate in nanowires was attributed to the variation of dipole field caused by the shape anisotropy.(3) To make the nanowires more applicable to the optoelectronic devices, biochemical and chemical sensors, we also designed and prepared the aligned composite fibers by adding an assistant collector and study the mechanism of the aligned fibers. Digital photographs and SEM showed that the aligned nano-composite fibers were uniform size.