Study On The Fluorescence Characteristics Of YF 3 :Eu 3+ Particles

Rare earth fluoride crystals known for its lower lattice vibration frequency,which could minimize the non-radiation relaxation caused by phonon interaction.Moreover,the atomic radius of yttrium in +3 oxidation state is similar to that of most lanthanide atoms,so that a relatively high doping level can be achieved without changing the crystal structure of the nanoparticles.With more and more researches in bio-applied cases,seeking for better chemical stability and lower cytotoxicity is is the mainstream of today's research direction.Due to rare-earth fluoride nanocrystals's unique luminescent properties and great potential applications in optics,optoelectronics,biomarkers,a considerable number of researchers have been attracted in the study of controllable synthesis and diverse morphologies of rare earth fluorinated nanocrystals.The fluorescence emission eficiency of the rare earth ion doped luminescent materials is closely related to the crystal structure of the matrix material,the local symmetry of the rare earth luminescent ions and morphology.The lattice distortion of the matrix and the reduction of the matrix structure symmetry caused by the rare earth ions in different matrices will lift the f-f electronic parity prohibition transition.At present,we are looking for chemical stability and high luminous efficiency nano-materials.Therefore,we have synthesized six different morphologies of YF3:Eu3+.Then,the effects of morphology and structure on the fluorescence properties of YF3:Eu3+ particles were studied in powder and single particle ways.This article mainly includes the following aspects:In the first part,YF3:Eu3+ was synthesized by coprecipitation method with green and low energy consumption.Then,the intrinsic relationship between the morphology,crystallinity,local symmetry and fluorescence emission performance of these five YF3:Eu3+ crystals were carefully studied.It was found that the fluorescence emission properties were also changed with the change of morphology.Also,the fluorescence emission spectra of the samples with the same crystal structure are different,and the fluorescence intensity depends on the crystallinity of the samples deeply.Among the bundle-like,dumbbell-like and rice-like samples,although the crystal structure is the same,but the dumbbell-like sample with high crystallinity has the highest fluorescence emission intensity.Both the structure of the octahedral and spherical samples have similar fluorescence emission spectrum,and the phase structure is the same,but the fluorescence emission intensity of the octahedral sample is stronger due to the better crystallinity.In conclusion,campare the crystallinity of two groups of samples,higher crystallinity means higher fluorescence intensity.For the two group of samples which have similar crystal structure,although the sample morphologies are different,but the influence of crystallinity on fluorescence emission intensity can not be ignored.At the same time,it was found that the fluorescence emission spectra of spherical and octahedral YF3:Eu3+ crystals were cleaved and red shifted,because of the crystal structure and the surrounding local field environment is diffremt.As a result,that makes difference in the amount of splitting,and the difference in the magnitude of the movement.In the second part,then we study the fluorescence emission spectra of single particles of different morphologies.The results show that the emission efficiency ofsingle octahedral YF3:Eu3+ is the highest at the same excitation condition,also the emission intensity is the highest.what's more,the experimental results are consistent with the results collected by the powder form.It is found that the fluorescence emission intensity of octahedral YF3:Eu3+particles is positively correlated with the particle size and number,and the overall luminescence intensity is improved and the shape of the line does not change at all.In the study of the polarization excitation of rice-like YF3:Eu3+ particles,the fluorescence emission intensity has a certain dependence on the angle of polarization of the excitation laser.In addition,it was found that the emission spectra of spherical YF3:Eu3+ single particles were different for the emission spectrum of the powdery samples.The intrinsic reason was the scattering of the excitation light and the loss of energy.