基于单颗粒NaYF_(4)微米棒的上转换白光发射特性

Upconversion white-light emission luminescence characteristics based on single-particle NaYF_(4)microrod

上转换白光材料在固态照明、液晶显示器和生物成像等领域展现出其他光源无法比拟的优势,倍受研究者们广泛关注.为此,本文采用水热法合成了一系列掺杂不同离子浓度的NaYF_(4)∶Yb^(3+)/Re^(3+)/Tm^(3+)(Re^(3+)=Ho^(3+),Er^(3+))微米晶体.在980 nm近红外光激发下,通过调控掺杂离子的浓度,研究Ho^(3+)/Tm^(3+)及Er^(3+)/Tm^(3+)共掺杂单颗粒NaYF_(4)微米晶体的白光发射特性.研究表明:在NaYF_(4)∶Yb^(3+)/Ho^(3+)/Tm^(3+)微米晶体中,通过调控Yb^(3+)离子的掺杂浓度易于实现其白光发射;而在NaYF_(4)∶Yb^(3+)/Er^(3+)/Tm^(3+)微米晶体中,通过调控Er^(3+)离子的掺杂浓度易于实现其白光发射.根据不同掺杂体系中微米晶体的发光特性,揭示了白光发射调控的物理机理,即主要是借助掺杂离子间交叉弛豫及能量反向传递过程而实现.同时,通过包覆NaYF_(4)惰性壳进一步有效增强了微米棒上转换白光发射.结果表明,通过离子掺杂技术及构建核壳结构不仅可实现微米棒的上转换白光发射,且可为进一步增强微米棒发光特性提供重要的实验参考,拓展微米晶体在显示、光电子技术及防伪等领域中的应用.

White upconversion(UC)luminescent materials have shown incomparable advantages over other light sources in the fields of solid-state lighting,liquid crystal display,and bioimaging,and received extensive attention from researchers.In this work,a series of microcrystals doped with different ion concentrations is synthesized by hydrothermal method,such as NaYF_(4):Yb^(3+)/Ho^(3+)/Tm^(3+)and NaYF_(4):Yb^(3+)/Ho^(3+)/Tm^(3+),and their corresponding micron core-shell(CS)structures are constructed based on epitaxial growth technology.The structure and morphology of the prepared microcrystals are characterised by X-ray diffractometer(XRD)and scanning electron microscope(SEM),showing that the microcrystal has a pure hexagonal-phase crystal structure with a rod-like shape.Under the excitation of 980 nm near-infrared laser,the white UC luminescence characteristics of Ho^(3+)/Tm^(3+)and Er^(3+)/Tm^(3+)co-doped single-particle NaYF_(4)microcrystals are systematically studied by modulating the concentration of the doping ions.The study shows that in Ho^(3+)/Tm^(3+)co-doped NaYF_(4)microcrystals,white UC luminescence can be easily achieved by modulating the concentration of Yb^(3+)ions,while in the Er^(3+)/Tm^(3+)co-doped NaYF_(4)microcrystal,the white UC luminescence can be effectively achieved by modulating the concentration of Er^(3+)ions.According to the luminescence characteristics of the microncrystals in different doping systems,the physical mechanism of white light emission regulation is revealed,which is mainly due to the interaction between the doped ions,including cross relaxation(CR)process and energy back transfer(EBT)process.Meanwhile,an effective enhancement of the white UC luminescence on CS microrod is achieved by coating the NaYF_(4)inert shell.Therefore,ion doping technique and the construction of CS structure can not only realize the white UC luminescence of microrods,but also provide important experimental reference for further enhancing the luminescence characteristics of microrods,and expand the applications of microcrystals in the fields of display,optoelectronics and anti-counterfeiting.