Study On Preparation And Near-Infrared Luminescent Properties Of Inorganic Phosphors Doped Rare-earth Ions

Recently,doped Er³⁺,Nd³⁺ and other rare earth ions of near infrared luminescent materials have been received extensive attention,due to the near-infrared light having many advantages of strong penetrability,deep tissue imaging,having no harm to the tested substances,free of background and high sensitivity in biological analysis.The near infrared luminescent intensity of inorganic materials doped rare earth ions is still weak,has not yet reached the immunoassay requirement.In this paper,the intentions are to improve the strength of near-infrared luminescent intensity and resolve the biocompatibility of nanoparticles.The conclusions and results were summarized as follows:MgWO₄ and Nd³⁺doped MgWO₄ powders were prepared by hydrothermal method.Studies showed that a pure phase of MgWO₄ crystal without crystalline H₂O can be synthesized at 180～230℃of hydrothermal temperature,8～10 of pH value and more than 24-hour of hydrothermal time.The as-prepared has a tetragonal structure and transfer to monocline structure when sintered at 850℃or higher temperature.With the calcination temperature increase,the flake shape samples changed to well dispersed Rod-like particles and an optimized sintering condition is 1050℃for 3 hours.Energy transfer from WO₄^2- group to Nd³⁺ ions was found.YAG:Ce³⁺,Nd³⁺powders were prepared by co-precipitation method.It was found near-infrared luminescence of Nd³⁺ in YAG could be very efficient sensitized with co-doped Ce³⁺, and the NIR emission intensity is almost 55 times of that of YAG:Nd³⁺when excited with a 470nm of an argon laser.The energy transfer mechanism from Ce³⁺ to Nd³⁺ was proposed.The influences of sintered temperature and the dopant concentration were investigated,and the strongest NIR emission of YAG:Ce³⁺,Nd³⁺ samples was obtained when sintered at 1500℃for 4h and doped with 5-6%Ce³⁺ and 5%Nd³⁺.Sr₂SiO₄:Eu²⁺,Nd³⁺samples were synthesized by a solid state method.The effects of sintering temperature,Eu²⁺-concentration on the Sr₂SiO₄:Eu²⁺ luminescence properties were investigated and found that the emission center red-shift with the increase of sintering temperature and Eu²⁺-concentration.It was found that energy transfer from Eu²⁺ to Nd³⁺ in Sr₂SiO₄:Eu²⁺,Nd³⁺ samples,and that mechanism was discussed simply.CaWO₄:Eu³⁺ nanoparticles were synthesized via hydrothermal micro-emulsion.The effects of hydrothermal temperature,hydrothermal time,initial pH and concentration of reactants on the CaWO₄:Eu³⁺ morphology and size were investigated.The uniform morphology and moderate grain size within 100nm particles were attained under the optimum reaction conditions.The core shell structure of CaWO₄:Eu³⁺/SiO₂ were attained for resolving the biocompatibility and made it has the potential application to fluorescence immunoassay.