The Preparation And Poperities Of Rare Earth Doped With Upconversion Luminescence Nanomaterials

The upconversion luminescent nanocrystals of Yb₃Al₅O₁₂（YbAG）based on three colors of R-G-B have been prepared by sol-gel methed and the green upconversion luminescent nanomaterials in the Er-Yb-Mn codoped LaMgAl₁₁O₁₉（LMA）have been prepared by co-precipitation method respectively.The doping elements and concentration on phase structures,surface morphology and upconversion emission properties were investigated by using x-ray diffraction（XRD）,scanning electron microscopy（SEM）,up-conversion emission measurement,to explore the up-conversion emission mechanism of Er（Tm）-Yb,Er（Tm）-Yb-Mo and Er-Yb-Mn system.The Er:YbAG nanocrystal obtained the green upconversion luminescence of center wavelength around 530 nm and 560 nm,and the red upconversion luminescence of center wavelength around 655nm,by 980nm semiconductor laser diode（LD）excitating,in which mainly was the red.The Mo codoped Er:YbAG nanocrystal obtained strong green upconversion luminescence.Due to forming Yb³⁺-MoO₄²polymer in Er-Mo:YbAG system,the green upconversion luminescence intensity 250times compared with the Er:YbAG nanocrystal through a high excited state energy transfer（HESET）from the|²F_7/2,³T₂>state of Yb³⁺-MoO₄^2-dimer to the ⁴F_7/2/2 level of Er ion,resulting in a strong enhancement of green upconversion emission.The blue and red upconversion emissions originating from the radiative transition of ¹G₄→³H₆ and³F₂→³H₆,¹G₄→³F₄ of Tm ion were obtained from Tm-Mo:YbAG nanocrystal.The process of a high excited state energy transfer from the|²F_7/2,³T₂>state of Yb³⁺-MoO₄^2-dimer to the ¹G₄ level of Tm ion,which can increase the internsity of the blue upconversion emissions of Tm ion.The stronger green and weaker red upconversion luminescence were obtained from Er-Yb-Mn:LaMgAl₁₁O₁₉9 nanocrystal,by using the 980 nm LD excitation.The intense green UC emission arises from a novel high excited state energy transfer（HESET）with|²F_7/2,⁴T_1g>(Yb³⁺-Mn²⁺dimer)to the ⁴F_7/2(Er³⁺),which significantly avoids the nonradiative decay processes.