Syntheses,Luminescent Properties And Application Of Core-Shell Structured Sulfide Phosphor

Sulfide phosphors have potential application prospects in many fields such as lighting,optical agriculture and anti-counterfeiting because of its excellent spectral characteristics,simple synthesis process and low cost.However,sulfide phosphors face a series of challenges,including poor stabilities and low light efficiency,which have severely restricted their practical applications.In this paper,several core–shell structured chalcogenide phosphor were synthesized on the basis of calcium sulfide and zinc sulfide.Furthermore,we also explored their applications in plant growth and dynamic anti-counterfeiting.1.One-step design to a water-resistant CaS:Eu²⁺,CaBr₂,CaF₂ composite phosphor.Unlike the conventional surface modifications upon application of postprocessing,this work proposes a simple one- step strategy for synthesizing the two-additive modified CaS:Eu²⁺,CaBr₂,CaF₂ composite phosphor.The role of double halides and the formation mechanism of modified phosphors were discussed in detail.The modified phosphor maintains a stable phase composition against moist atmosphere and water immersion.The red emission of the as-obtained CaS:Eu²⁺,CaBr₂,CaF₂ phosphor is three times as intense as that of nonmodified CaS:Eu²⁺.In addition,the agricultural film fabricated with the modified phosphor presents brilliant light conversion performance and great weather resistance.2.Inward erosion growth to a super stable core–shell structured CaS:Eu²⁺@CaZnOS red phosphor.A core–shell structured CaS:Eu²⁺@CaZnOS phosphors were synthesized by a convenient solid-state method.The CaZnOS protection layer is formed due to inward incorporation of ZnO into the surface lattice of the CaS substrate.The result shows that the as-obtained surface modified red phosphor shows super stability and emissive activity toward acidic,basic and aqueous solutions.Moreover,the emission intensity at 150°C remains over 95% of that at room temperature.In addition,the quantum efficiency.of the optimal core–shell structured phosphor reached 68.78%at 550 nm, which is elevated by 23%compared to that of the original CaS:Eu²⁺. This is the first time to simultaneously realize a chemically and thermally stable sulfide phosphor,along with high quantum efficiency, which exhibits great suitability for light-emitting diodes and solar spectral conversion films for facilitating plant growth.3.A dual-UV/green-excited and dual-red-emitting spectral conversion phosphor CaS:Eu²⁺@CaZnOS:Mn²⁺with all-weather resistance. The existence of CaZnOS shell on CaS:Eu²⁺@CaZnOS phosphor seriously hinders the UV-to-red conversion in CaS:Eu²⁺.Based on this,we structure CaS:Eu²⁺@CaZnOS:Mn²⁺composite phosphor with dual-UV/green-excited and dual-red-emitting spectral conversion ability by inward erosion growth method.In addition to the super chemical durability and thermal stability conferred by CaS:Eu²⁺@CaZnOS,the addition of Mn²⁺in shell CaZnOS qualifies the phosphor with strong UV absorption,contributing to the improvement of the anti-photodegradation of the CaS:Eu²⁺core.The additional UV-to-orange red conversion further extends the red components required by indoor plants.Therefore,this super stable dual UV/green excited and dual red- emitting CaS:Eu²⁺@CaZnOS:Mn²⁺phosphor can be used as a universal spectral converter for plant cultivation.4.A ultraviolet resistant multi-mode dynamic luminescent phosphor ZnS:KBr,Mn²⁺@CaZnOS.ZnS:KBr,Mn²⁺phosphors with multi-mode dynamic luminescence properties are obtained by constructing intrinsic luminescence center and doped luminescence center in a crystalline lattice at the same time.One is the dynamic change of excitation mode:the phosphor emits different colors under 302 nm and 365 nm UV lamps.One is the time mode:after removal of UV lamp, the phosphor exhibits an orange afterglow that is different from its photoluminescence(PL)color.Moreover,the dynamic PL and afterglow is associated with the interactions between two PL centers and traps in the material.Finally,ZnS phosphors are extremely unstable under ultraviolet light irradiation.Hence,a series of CaZnOS-coated ZnS:KBr,0.1%Mn²⁺phosphors were synthesized.In-depth analyses of Infrared,SEM and HRTEM prove the existence of CaZnOS coating layer.The emission intensity of the coated sample remains 91.4%of its original intensity after 45 days of continuous UV lamp irradiation,while the emission intensity of the uncoated sample sharply drop to 50.5%of its original intensity.Therefore,this stable multi-mode dynamic phosphor have great application potential in advanced dynamic anti-counterfeiting.