| Up-conversion luminescence nanomaterials(UCNPs)can convert two or more low-energy photons in recent years,and then emit a high-energy photon with large antiStokes shift,long life,and low excitation power density.Therefore,it is widely used in many fields,such as "solid-state lasers,three-dimensional displays,anti-counterfeiting technology,biological imaging,solar cells,temperature sensors,and ion detection.However,considering that the low luminescence efficiency of up-conversion nanomaterials.in order to broaden the scope of application,this paper synthesized Lu6O5F8 and GdVO4 nanocrystals by co-precipitation method,and studied the upconversion luminescence(UCL)intensity and color under multiple excitation wavelengths.In addition,the UCL intensity can be improved by doping non-emitting center ions to change the symmetry of the lattice and the dual wavelengths synergistic effect,which can be further applied in temperature sensing,solar cells and ion detection.(1)In this work,a series of GdVO4:Ln3+with similar size and irregular prismatic shape were successfully prepared by a co-precipitation technique.In the research of UCNPs,most of the literatures use 980 nm as the excitation wavelength,but in this work,based on the application of solar cells,we studied the UCL performance under multi-wavelength excitation(980,808,1550 nm).It is worth pointing out that among all the studied GdVO4:Yb3+/Tm3+,GdVO4:Yb3+/Er3+/Nd3+,GdVO4:Yb3+/Er3+,GdVO4:Yb3+/Er3+/Ho3+,GdVO4:Er3+/Ho3+,GdVO4:Yb3+/Er3+/Ho3+/Tm3+,GdVO4:Er3+samples,only GdVO4:Yb3+/Er3+ has a dual-wavelength(980 nm+1550 nm)synergistic effect.Compared with single wavelength excitation,the luminescence intensity of dual wavelength excitation increased by 1.87 times.In addition,in order to further improve the UCL intensity,the cation(Lu3+/Y3+)and anion(PO43-)were doped into GdVO4:Yb3+/Er3+,which enhanced the luminescence intensity by nearly three times.Combining the above experimental phenomena,the number of pump power photons and the energy level diagram of rare earth ions,the possible energy transfer and UCL mechanism are discussed in detail.At the same time,based on the temperature sensing application of UCL in recent years,the temperature sensing effect of GdVO4:Yb3+/Er3+at 980 nm and 1550 nm was studied in detail.High Sa(0.0069 K-1)and Sr(1.13%K-1)were obtained in the temperature range of 273-453 K.The modulation of various excitation wavelengths enhances the UCL intensity and the sensitivity of temperature measurement,so the multifunctional GdVO4:Ln3+is expected to be applied to temperature sensors and solar cells.(2)The Lu6O5F8:1%Er3+/10%Yb3+UCNPs with uniform morphology were successfully prepared by a co-precipitation method.The size of the nanomaterials was about 10 nm.In order to increase the UCL intensity,the lattice symmetry and the nonradiative relaxation transition are reduced by doping lanthanide ions(Y3+,Gd3+).Under 980 nm(1550 nm)excitation,the red UCL intensity of(Lu0.79Y0.1)6O5F8:1%Er3+/10%Yb3+ and(Lu0.85Gd0.04)6O5F8:1%Er3+/10%Yb3+ UCNPs is 4.67(19.3)times and 3.95(8,89)times higher than that of the samples without Y3+ and Gd3+ doping,respectively.Meanwhile,the temperature sensing effect of the thermally coupled energy level(Er3+:2H11/2,4S3/2)and the non-thermally coupled energy level(Er3+:2H11/2,4F7/2)of this Lu6O5F8:1%Er3+/10%Yb3+has also been investigated in detail.The sensitivity is as high as 0.087 K-1.Interestingly,Lu6O5F8:1%Er3+/10%Yb3+can be used to detect the metal Cu2+.Metal ions(Na+,Mg2+,Al3+,Fe2+,Co2+,Cd2+,etc)cause low UCL quenching at 980 nm,while Cu2+ causes 90%UCL quenching of Lu6O5F8:1%Er3+/10%Yb3+under the same conditions. |
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