Preparation And Properties Of Long Persistent Luminescent Sulfides Excited By Blue Light

Traditional oxide-based luminescent materials have the advantages of strong luminescence,high stability,and long afterglow time.However,due to the large band gap,it is often necessary to use ultraviolet or deep ultraviolet light for excitation.Ultraviolet or deep ultraviolet photons have high energy,which means that when these materials are used in the lighting field,they need to be provided with high-energy and stable excitation sources,which are difficult to meet the requirements of energy saving and environmental protection.In addition,nano-long afterglow materials have shown great application prospects in biological cell imaging and targeted therapy,but biological tissues have strong absorption of ultraviolet light or deep ultraviolet light,which means that this type of nano-length dependent on ultraviolet excitation Once the afterglow luminescent material enters the body,it cannot emit light through external light excitation.Therefore,if a material that can be excited by long-wavelength photons can be prepared,the energy demand of the excitation source can be effectively reduced,and the concepts of energy saving and environmental protection can be met.The effective transmission windows of biological tissues are 700-1000 nm and 1100-1350 nm,which means that if near-infrared long-afterglow luminescent materials with near-infrared light with a wavelength of about 700 nm as the excitation light source can be developed,then for biological tissues,cell monitoring imaging and other research have practical significance.Therefore,the design and research of narrow band gap luminescent materials that satisfy blue light or longer wavelength excitation,strong luminescence,and stability have become the current research focus.In this thesis,considering the material cost,environmental protection and other factors comprehensively,the narrow band gap sulfide matrix luminescent materials are selected for research,in order to obtain long-wavelength excitation and excellent performance long-lasting materials.The research content and main results of this paper are introduced as follows:(1)In the ZnS:Mn²⁺/Ge⁴⁺luminescent material co-doped with Mn²⁺and Ge⁴⁺,due to the co-doping of Ge⁴⁺ions,when the material is excited by 466 nm blue light,the 585 nm yellow light emission intensity of Mn²⁺ions is that of single-doped Mn²⁺ions.560%.This is because there is energy transfer between Ge⁴⁺ions and Mn²⁺ions,that is,electrons in Ge⁴⁺ions that transition to high energy levels move to Mn²⁺ions,and then transition downwards with the electrons of Mn²⁺ions themselves,thereby causing the yellow light emission of Mn²⁺ions.The intensity is greatly improved.In addition,the afterglow of the material is also significantly enhanced when Mn²⁺and Ge⁴⁺are co-doped.(2)Using inert gas combined with sublimed sulfur element,the reduction reaction of sulfur substitution was realized by high temperature solid phase method,and ZnGa₂S₄:Cr³⁺luminescent material was successfully prepared,which can emit near-infrared under excitation at 442 nm and 600 nm wavelength.Light,and its band gap is smaller than ZnS:Mn²⁺/Ge⁴⁺.However,this material can only emit weak red light and long afterglow when excited by blue light,and the afterglow time is short.This may be because the material composition does not contain O atoms,so O vacancies cannot be formed during the synthesis of the material,while S does not There are vacancies,which ultimately leads to weak long afterglow luminescence.(3)The Ca₈Al₁₂O₂₄S₂:Eu²⁺luminescent material was successfully prepared by the two-stage high-temperature solid-phase method of synthesis and reduction stepwise reaction,and it was found that the optimal reduction reaction temperature for the preparation of this material was 980?.After irradiated by a 460 nm blue LED,the material emits an obvious red long afterglow of 648 nm,and has a strong initial intensity,and the afterglow decay time is more than 10 minutes.After testing and calculation,the band gap of the material is as small as 2.89eV.Obvious long afterglow luminescence is obtained in such a narrow band gap material,which has very important guiding significance for future research.