Preparation Of Rare Earth-doped Bismuth Oxychloride Ultra-thin Nanosheets And Research On Their Luminescence Properties

In recent years,two dimensional?2D?material,especially graphene,has attracted much attention.Due to its lamellar structure and the thickness is only the thickness of a single atomic layer or several atomic layers,the electron transfer is confined in a two-dimensional plane.Therefore,2D nanosheets exhibit unique physical,chemical,electronic and optical properties.The fluorescence characteristics of rare earth?RE?ions is usually related to the environment of the crystal field.Here,we combine 2D nanosheets with rare earth ions to investigate unique phenomenon,which contributes to the development of expanded potential application materials.Firstly,by optimizing the conditions of solvent,ultrasonic time and ultrasonic frequency,the BiOCl nanosheets is successfully prepared by ultrasonic assisted liquid phase stripping method.After further centrifugation,the samples are obtained with different thickness distribution by using the different centrifugal force,which laid the foundation for the next test.Subsequently,we study the relationship between the fluorescence characteristics and the BiOCl nanosheets thickness by the ultrasensitive spectroscopic fingerprints of Eu³⁺ions dopants.It is found that the different thickness of the BiOCl nanosheets can cause the change of the polarization field,resulting in the change of the fluorescence branching ratio of some sensitive transitions and a unique fluorescence phenomenon.Due to the decrease of slice thickness,for the BiOCl nanosheets,the spontaneous polarization and the depolarization field increases simultaneously,which results in the increase of the fluorescence branching ratio of I?⁵D₀?⁷F₂?/I?⁵D₀?⁷F₄?.In order to further investigate the effect of the BiOCl nanosheets thickness,we also study the fluorescence characteristics of Er³⁺ion dopants.Compared with the nonultrasonic samples,it is found the photon avalanche phenomenon disappears and the photon number decreases,and I_red/I_green ratio increases with the film thickness reduced,which results from the change of depolarization field and quantum size effect,reducing the level of the particle population.Finally,we prepared BiOCl:Yb³⁺/Er³⁺nanosheets with different thickness by changing the content of ethanol and water during the synthesis process.It is found that the thickness of the sample decreases with the increase of ethanol content in the solvent,and the internal electric field increases,which leads to the increase of the red light upconversion luminescence intensity.