Synthesis Of Nanometer Core-Shell Fluoride Materials And Study Of Their Fluorescent And Optical Temperature Sensing Properties

With the rapid development of nanotechnologies,rare-earth(RE)doped nanometer materials have been found to have excellent properties in optics,electricity and magnetism.And RE doped nanometer materials have gained more and more popularities.Among these research fields,how to enhance the efficiency of solar energy and the sensitivity in optical temperature becomes the hot topic recent years.When it occurs to the application in crystalline silicon solar cells,the part(which wavelength is longer than 1100 nm)of solar energy will be lost for that the Si semiconductor can't absorb the energy below its band gap(1.12eV).So,it becomes a key factor to enhance the efficiency of solar energy with luminescence conversion materials.In this work,NaGdF4:12%Er3+ @NaGdF4:10%Er3+ active-core/active-shell nanoparticals(NPs)were peculiarly synthesized via a delayed nucleation pathway with procedures.The phase,shape,and size of the resulting core-shell NPs are confirmed by transmission electron microscopy and X-ray diffraction.Coated with an NaGdF4:10%Er3+ active shell on the NaGd F4:12%Er3+ core NPs,a maximum luminescent enhancement of about 336 times higher than the NaGdF4:12%Er3+ core-only NPs was observed under the excitation of 1540 nm.The intensity ratio of green to red was adjusted by changing Er3+ concentration in the shell.By analyzing the lifetimes of emission bands and exploring the energy transition mechanism,the giant luminescence enhancement is mainly attributed to the significant increase in the near-infrared absorption at 1540 nm and efficient energy migration from the shell to core.On the other hand,with the advantages of anti outside interference and anti excitation power,RE doped nanometer materials' application in the sensitivity of optical temperature also gained more and more attention.In this work,nanoparticles single-doped with Er3+ ions were synthesized with the hydrothermal method.Different morphologies were obtained by adjusting the components,procedures and temperatures to different extend.The test results of TEM further confirmed the morphologies.Under different morphologies,the properties based on the sensitivity of optical temperature were researched.The choice of thermal coupling level of Er3+ ion,the fitting of experimental data,and the sensitivity were figured out and compared in the work.At the same time,nanoparticles co-doped with RE(RE=Tm,Ho,Pr,Tb)ions were synthesized with a thermolysis procedure of trifluoroacetic acid salt.RE(RE=Tm,Ho,Pr,Tb)ions are chosen as activators and Yb3+ ion acts as sensitizers in the fluoride materials.The core material is NaYF4 with high conversion efficiency.With the optimal components as reported,different co-doped nanoparticels were compared with the properties of optical temperature sensitivity.As a result,Pr and Yb co-doped NaYF4 was considered as the best one in the application of sensitizing optical temperature,comparing to other conditions.