The Synthesis Of Rare Earth Ion-doped Fluorides And Red Upconversion Luminescence

Rare earth ion doped up-conversion luminescent material refers to a novel fluorescent material that absorbs two or more low-energy photons and emits high-energy photons,which have great potential applications in biomedical imaging,solar cells,optical anti-counterfeiting,etc,for Its many advantages,such as low toxicity,stable chemical properties,good fluorescence performance etc.In recent years,it has become a hotspot for many scholars.Nanoparticles with high-purity,single-band red up-conversion luminescence are more suitable as biomarkers because red light in the 600-700 nm range penetrates deeper into the biological tissue,and secondly red light loses less energy from biological tissue scattering.So the red up-conversion luminescence has greater biological application value.However,due to the large non-radiative transition between the 4f-4f energy levels of trivalent rare earth ions,it is difficult to obtain pure red up-conversion luminescence.Therefore,it is the research focus of this paper to prepare high-performance red up-conversion luminescent nanoparticles suitable for biological applications.In view of the above research questions,the main research contents of this paper are as follows:Firstly,NaGdF4:Yb/Er nanocrystals doping with Sc3+ ions were successfully synthesized by solvothermal method.Due to the small radius of Sc3+,it is easy to be doped into other matrix materials to adjust the luminescence properties.With Sc3+ ions doped,it was found that a new crystalline phase,Na3ScF6,was formed,and the morphology of the sample also changed greatly.When the sample was excited by 980 nm infrared light,the green and red upconversion of Er3+ was detected.The up-conversion luminescence was the strongest in the sample with 20mol%of Sc3+,which was 4.7 times of that of the sample without Sc3+.Furthermore,a series of NaScF4:Yb/Er nanocrystals were synthesized by hydrothermal method.The up-conversion luminescence of Er3+ ion from green to red was realized by tuning the reaction time from 12 hours to 2 hours.When the reaction temperature was 200 ?,only the amount of a raw material of NH4F was changed,a pure cubic phase ScF3:Yb/Er,a hexagonal phase NaScF4:Yb/Er and a pure cubic phase(NH4)2NaScF6:Yb/Er were prepared respectively.Under the excitation of 980 nm infrared laser,multi-color up-conversion luminescence of Er3+ ions was realized.In order to further improve the performance of up-conversion luminescence in the red 600-700nm range,Ho3+ is used as the illuminating center.LiGdF4:Yb/Ho nanomaterials were synthesized by oil thermal method.By doping different concentrations of Ce3+(0-16mol%),nanorods with a length of about 500nm were obtained,and the samples were uniform in morphology and good in dispersibility.Under the excitation of 980 nm infrared light,the 5S2/5F4?5I8 transition of Ho3+ at 540 nm and the 5F5?5I8 transition at 642 nm were detected.It is found that as the Ce3+doping concentration increases from 0 mol%to 16 mol%,the relative intensity of the two main up-conversion luminescence of Ho3+ changes significantly,the red light emission enhancement is larger,and the green light enhancement is smaller,when Ce3+When the concentration increased to 16 mol%,the red-green ratio of Ho3+ luminescence intensity increased from 0.179 to 3.46,which was nearly 20 times stronger.The CIE color map showed that the spectral color changed from green to red.Furthermore,a series of Mn2+ doped NaLuF4:Yb/Ho up-conversion nanomaterials were synthesized by oil-thermal method,and the mechanism of red emission was analyzed.Firstly,a series of nanocrystals were synthesized by changing the Mn2+doping concentration(x=0mol%,10mol%,20mol%,30mol%,40mol%,50mol%)at reaction temperature of 150?,and the different structures and composition of synthesis of nanomaterials were analyzed.Under the excitation of 980nm laser,the green luminescence of Ho3+ was detected.It is located at 540nm,mainly from the 5F4?5I8 energy level transition.The red luminescence is located at 645nm,mainly from the energy level transition of 5S2?5I8.The luminescence of Mn2+ is not detected which indicates that Mn2+ is not excited at 980 nm excitation.It is found that,with the change of Mn2+ doping concentration,the relative intensity of Ho3+'s green and red up-conversion luminescence changes.When the Mn doping concentration is 30 mol%,the red-green light luminescence intensity ratio is the largest.Subsequently,the Mn2+doping amount of the sample was kept at 30mol%,and a series of nanomaterials were synthesized by changing the reaction temperature.The results show that as the reaction temperature increases,the crystallization of samples becomes better,the red light becomes relatively weaker,and the mechanism of up-conversion luminescence is analyzed.