The Controllable Synthesis And Luminescence Properties Of The Near-infrared,Upconverting And Afterglow Oxide Nanophosphors

The upconversion nanomaterials can convert low-frequency photons into high-frequency photons,which often emit visible light or near-infrared brightness.It has attracted more and more attention.The long afterglow material is a kind of energy storage material that can last for several minutes or hours after the stoppage of the excitation.The unique optical properties of up-conversion luminescence and long afterglow nanomaterials were effectively combined,which has caused more and more people's attention in recent years.Because it has potential application value in many fields especially in the area of biomedical imaging and medical diagnosis.The intense red up-conversion luminescence in Sc₂O₃:Yb³⁺,Er³⁺synthesized using a biphasic solvothermal?ST?method was observed upon laser diode pumping at 980 nm.Compared with that found in the bulk sample synthesized using a solid state?SS?reaction at the same sintering temperature?700°C?,the green and red up-conversion luminescence are enhanced by a factor of 19.7 and 23.4,respectively.The relative red intensity of the sample prepared using the ST method at 700°C for 2 h was enhanced up to 6.6 times compared to that obtained by the SS reaction method at 1600°C for 6 h.On analyzing the spectral distribution,power dependence and decay curves of Yb³⁺,we revealed that the red emission of the Er³⁺:⁴F_9/2 level in Sc₂O₃:Yb³⁺,Er³⁺was populated via three possible routes,i.e.excited-state absorption?ESA?,two-step energy transfer up-conversion?ET?and non-multiphonon relaxation mechanism from the(²H_11/2,⁴S_3/2)via cross-relaxation and energy back transfer?CRB?.For the green up-conversion of the Er³⁺:(²H_11/2,⁴S_3/2)level,a three-photon process described as Yb³⁺:²F_5/2+Er³⁺:⁴F_9/2?Yb³⁺:²F_7/2+Er³⁺:²H_9/2occurs in the Sc₂O₃:Yb³⁺,Er³⁺material.The results indicate that ST-Sc₂O₃:Yb³⁺,Er³⁺can act as an efficient up-converting red light emitter and ST-Sc₂O₃ is an appropriate oxide host for up-conversion luminescence.Yb³⁺,Er³⁺,Cr³⁺co-doped ZnGa₂O₄ upconversion luminescence and persistent luminescence sub-nanoparticles was synthesized by the two-phase method with oleic acid and toluene as auxiliary materials in this paper.Crystal structure,photoluminescence?PL?,microstructure and afterglow properties of the prepared nanoparticles were analyzed by X-ray diffraction?XRD?,TEM and fluorescence spectrometer.Samples could be ultraviolet light and near-infrared 980 nm effectively excited.They can be observed near-infrared light with the peak at 696 nm and red light emission in 630-700 nm range.After the stoppage of the excitation,it could be also observed near-infrared light emission at 696nm by the uv light?254 nm?,red?650 nm?and 980 nm light stimulated.At the same time,the upconversion and the afterglow emission variation of different Yb³⁺doping concentrations were studied,and the decay rate was the most slowest at the concentration of 10 mol%because of the increase of the traps.The photophysics mechanism of the time growth and multi-mode excitation were revealed by the mechanism of afterglow luminescence and the mechanism of photophysics studied.