Er ^{3 +} And Yb ^{3 +} Doped Zro ₂ Preparation And Up - Conversion Luminescence Properties Of Nano - Materials

Upconverting nanophosphors are one of the most promising materials for a variety of applications in solid-state lasers, fluorescence biolabels, and so on. The use of these nanocrystals directly for biological applications is limited because of their very low solubility in water. It is necessary to develop suitable methods for synthesizing upconversion nanocrystals that are dispersible in water and many organic solvents, and also have some functional chemical groups on their surfaces for conjugation of biomolecules. The silica coating can improve the solubility in water and biocompatibility of the nanocrystals, so silica coated nanocrystals can be used to the fluorescence biolabels.Rare earth doped ZrO₂ nanocrystals were prepared in a nonionic reverse microemulsion. In the ZrO(NO3)2·H2O solution, different concentration of Tm(NO3)3 or Er(NO3)3 and Yb(NO3)3 were added to inform the water phase. Cyclohexane was used to the oil phase, polyoxyethylene (5) nonylphenyl ether (NP-5) and polyoxyethylene (9) nonylphenyl ether (NP-9) as surfacers to gain reverse microemulsion. The precursor was obtained through demulsified by adding acetone, then rare earth doped ZrO₂ nanocrystals was informed after calcined at high temperature. XRD patterns of ZrO₂ nanocrystals showed that the highly crystalline cubic structure of the ZrO₂ nanocrystals without other phase. In SiO2-coated ZrO₂ nanocrystals, SiO2 shell can be seen clearly.In Er³⁺ codoped ZrO₂ nanocrystals and Er³⁺and Yb³⁺ codoped ZrO₂ nanocrystals, the green and red bands arise from Er³⁺–Er³⁺or Yb³⁺–Er³⁺ pairs via a two-photon process according to upconversion luminescence spectra and the energy level of rare earth irons. In Yb³⁺ and Tm³⁺ codoped ZrO₂ nanocrystals, the bright blue emissions arise from a three-photon excitation process. From upconversion luminescence spectra analysis, the intensity of SiO₂ coated nanoparticles is weaker than that of SiO₂ uncoated nanoparticles, because the phonon energy is increased. In Er³⁺, Yb³⁺ co-doped ZrO₂, when the concentration of Er³⁺ is 1%, the red emission intensity is greatly enhanced with the increasing of the the concentration of Yb³⁺. This is mainly causes by the Yb³⁺ ion sensitization enhancement. This indicated that there is the shift from ⁴S_3/2/²H_11/2â†'⁴I_15/2 to ⁴F_9/2â†'⁴I_15/2.