Study On Synthesis And Upconversion Properties Of Yb/Tm/GZO Nanocrystalline

With the coming of the new century, upconversion nanoparticles have been an advanced research hotspot. Lanthanide-doped GZO has electrical properties as well as upconversion optical properties, which has a potential application prospect. Further more, the abundant raw material, easily prepared and non-toxic make the GZO nanomaterial have a widespread application in the field of biomedical science, optics and physics.In this paper, Yb³⁺/Tm³⁺/GZO nanocrystalline were successfully prepared via hydrothermal method. The optimum process parameters have been determined by XRD analysis, SEM morphology analysis and upconversion emission analysis. The optimal hydrothermal reaction temperature and time were 150 ℃ and 24 h with Cit3-as dispersant. The samples were prepared with different dispersants, and the mechanism was confirmed via morphology analysis. Then the Yb³⁺/Tm³⁺/GZO nanorods, uniformly distributed and smaller sizes, were synthesized under the optimum process parameters. Raman spectroscopy was taken and the result shows the highest phonon energy of GZO is 508 cm-1, which is a good choice as a matrix of upconversion luminescence material.Factors such as quenching ions concentration, concentration of rare earth ions and substrate defects, which affect upconversion emission have been studied. The quenching ions of OH- and CO₃^2- that remained through the hydrothermal synthesis process.OH- and CO₃^2- will influence UC property via increasing possibility of nonradiative relaxation. And we used annealing method to reduce the concentration of quencher ions, infrared analysis and analysis of upconversion emission spectrum were used to determine the annealing temperature of 580 ℃. The concentration of doped Yb³⁺ and Tm³⁺ ions can influence the transfer process of up-conversion phonon. The higher the doping concentration of rare earth ions, the greater the probability of non radiative relaxation. Matrix material defects can influence the upconversion property. Changing the mole ratio of [Ga³⁺]/[Zn2+] can change the particle size. For the better output of UC fluorescence, grainsize analysis were made to figure out the variation that size effect and surface effect have on the UC emission.Mechanism of upconversion luminescence through differernt pump powers has been studied. Upconversion mechanism analysis showed that a three-photon upconversion processis asigined to the blue emission, a two-photon upconversion processis assigned to the red emission. The blue emission generated by 1G4â†'3H6 level and the red emission generated by 1G4â†'3F4 level. By studying the relation of fluorescence intensity and CIE chromaticity values, we can theorize that the influence of the pump power on upconversion luminescence intensity.The UC spectrum of Yb³⁺/Tm³⁺/GZO has been tested under different temperature. The effect of temperature coupling level of 3F2, 3, 3H4 and fluorescence spectra were used to calculate FIR value, after linear fitting, the sensitivity coefficient has been figure out of 1589/T2 which is higher than many other rare-earth doped oxide system.