Preparation And Luminescence Properties Of 411-Type Zinc Borate Composites

As a new type of fluorescent material,carbon quantum dots have attracted the attention of many researchers due to their excellent luminescence properties.However,people pay more attention to the luminescence properties of carbon quantum dots in aqueous solution,but less attention to their luminescence in solid powder.The lack of research on luminescence in solid powders greatly limits the imagination that carbon quantum dots can be widely used.As a multifunctional inorganic material,borate has been widely used.Zinc borate has the characteristics of low price,low synthesis temperature,high chemical stability,changeable composition and morphology,etc.It is a new potential luminescent matrix material.In recent years,there have been some reports on the research of rare earth zinc borate luminescent materials,but most of the research has focused on anhydrous zinc borate matrix materials.Due to the existence of a large amount of hydrate zinc borate,it is of great practical significance to conduct research on luminescent materials based on hydrated zinc borate.To this end,in this paper,three series of zinc borate composites were designed and synthesized by the interaction between 411 type zinc borate?4ZnO·B₂O₃·H₂O,abbreviated as ZBH?and yellow light emission nitrogen doped carbon quantum dots?yNCDs?or rare earth thulium ion(Tm³⁺),and try to apply the resulting composites to near-ultraviolet LEDs.The specific research contents are as follows:Firstly,a series of ZBH:Tm³⁺composites were prepared by hydrothermal method.The changes of the structure,morphology and luminescent properties of ZBH:Tm³⁺composite with different doping amount of Tm³⁺were studied.The results show that under a certain amount of rare earth Tm³⁺doping,the zinc borate in the ZBH:Tm³⁺composite can still maintain the 411 type structure.A small amount of Tm³⁺only replaces part of Zn²⁺in zinc borate and doped into the matrix lattice.But with the increase of Tm³⁺doping amount,the rod-like structure of 4ZnO·B₂O₃·H₂O is gradually destroyed and tends to form a sheet-like structure.The fluorescence spectra show that Tm³⁺doping can significantly improve the fluorescence emission intensity of zinc borate.Under the excitation wavelength of 360 nm,When the Tm/Zn atomic percentage reaches 9 at.%,The ZBH:Tm³⁺composite has the strongest blue light emission.Secondly,a series of ZBH/yNCDs composites were prepared by hydrothermal method.The effect of yNCDs content on the structure,morphology and luminescence properties of ZBH/yNCDs composites were studied.The results show that when the yNCDs content is within a certain range,with the increase of yNCDs content,the morphology of the ZBH/yNCDs composite has evolved from rod-like to block to sphere-like.Under the excitation wavelength of 395 nm,ZBH/yNCDs composite with sphere-like morphology has the strongest white light emission.The addition of yNCDs regulated the luminescence properties of 4ZnO·B₂O₃·H₂O.However,when the content of yNCDs continued to increase,4ZnO·B₂O₃·H₂O in the ZBH/yNCDs composites gradually lost water and eventually became ZB/yNCDs?4ZnO·B₂O₃,ZB?composites.Finally,a series of ZBH:Tm³⁺/yNCDs composites were prepared by hydrothermal method.With the change of yNCDs content in the composite,the structure,morphology and luminescence properties of the ZBH:Tm³⁺/yNCDs composites were studied.The results show that the ZBH:Tm³⁺/yNCDs composite can be obtained within a certain range of yNCDs.When the yNCDs content continues to increase to a certain extent,the structure of 4ZnO·B₂O₃·H₂O in the ZBH:Tm³⁺/yNCDs composite will change.By changing the content of yNCDs in the composite,the morphology of the ZBH:Tm³⁺/yNCDs composite has changed significantly,and gradually evolved from the sheet-like to flower-like morphology.the ZBH:Tm³⁺/yNCDs composite with flower-like morphology has the strongest fluorescence emission,which can obtain nearly perfect white emission at 360 nm excitation wavelength.