Preparation,photo-responsive Mechanism And Application Of Germanate Long-lasting Materials

Rare earths doped inorganic persistent luminescent materials is one of the family of the leading luminescent materials.It has been widely studied and applied for its special luminescent properties.Conventional persistent luminescent materials usually emit specific wavelength,and display unitemporal and unimodal(occasionally bimodal)emission,resulting in low-level application field.The tunable optical characteristics of the persistent luminescent material,such as luminous color,lifetime and excitation mode,can promote the long afterglow material to have the stimulus response performance.The purpose of this dissertation is to investigate the multi-color and multi-mode luminescence of persistent luminescent materials.In this paper,it is found that a variety of optical properties,such as polychromatic fluorescence,persistent luminescence,up-conversion luminescence,photostimulated luminescence and other different optical properties are concentrated in a single material by doping different elements,and the emission mechanism of various doped elements in inorganic materials is analyzed.These findings offer unique insight for designing highly integrated stimuli-responsive luminescent materials and smart devices toward a wide variety of applications.The persistent luminescent fiber prepared by this material has great potential in the field of anti-counterfeiting and intelligent materials.The main research work and results are as follows:(1)The photo-response properties were researched by blending CaAl₂O₄:Eu²⁺,Nd³⁺,Sr Al₂O₄:Eu²⁺,Dy³⁺and Ca_0.25Sr_0.75S:Eu²⁺.Because of the different excitation and emission peaks of the three powders,the powders could emit tunable colors under different excitation conditions.The relationship between luminescence color and powder type,weight ratio and excitation source were further studied.Due to the wavelength response property,the blended powder can be used as special pigment in information encryption and anti-counterfeiting.(2)Three new types of photo-responsive persistent materials were prepared by high temperature solid-phase method,namely Na₂CaGe₂O₆:Pb²⁺,Y³⁺,Na₂CaGe₂O₆:Pb²⁺,Tb³⁺,and Na₂CaGe₂O₆:Pb²⁺,Mn²⁺,and Yb³⁺.The emission spectra show that there are two luminescent centers in all the materials.With the vary of excitation wavelength,relative emission intensity of the two luminous centers changes constantly.Afterglow property shows that only one luminescence center is charge for the luminescent property,and the afterglow color is different from fluorescence.The multi-photo-response luminescence makes it possible to be used in intelligent sensing materials.(3)The factors such as sintering temperature and doping content of powder were further tested and analyzed in detail.Eight different luminescent powders were prepared.In addition,the photo-response range was extended to near-infrared light by doping the luminescent ions Er³⁺and Tm³⁺.For the first time,photoluminescence,upconversion luminescence,afterglow luminescence and photo-stimulated luminescence were concentrated in the experiment.The luminous powder not only has complete luminous colors,but also has more optical functions.(4)Taking Na₂CaGe₂O₆:Pb²⁺,Mn²⁺,Yb³⁺,Er³⁺powder as an example,the luminescent mechanism of each dopant in the system was obtained by changing the content of different dopants,and the influence of various elements on the optical properties was analyzed.In addition,the effect of excitation conditions on emission spectrum was also discussed.The increase of Pb²⁺ratio will cause the red shift of blue emission light,Mn²⁺and Yb³⁺affect the red emission light together,and Er³⁺plays a decisive role in the up-conversion emission peak.In addition,by studying the effect of excitation conditions on the emission spectrum of the material,it is concluded that as the excitation time increases,the fluorescence intensity gradually increases until saturation;as the excitation aperture gradually increases,the fluorescence intensity first increases linearly,and then gradually stabilizes.(5)Three methods were used to prepare the photo-responsive luminscent fiber,and the preparation and application of light-responsive luminescent fiber were explored.The first method is the combination of Sr₂Zn Si₂O₇:Eu²⁺,Dy³⁺luminescent powder and rhodamine B yellow fluorescent dye.In the second way,CaAl₂O₄:Eu²⁺,Nd³⁺luminescent powder and Ca_0.25Sr_0.75S:Eu²⁺powder was combined to prepare the fiber.This method used the excitation spectra of the two powders at the ultraviolet and visible wavelengths respectively.The third way is to use Na₂CaGe₂O₆:Pb²⁺,Mn²⁺,Yb³⁺,Er³⁺noctilucent powder,after solution spinning method,prepared into fiber.The experiment shows that the fiber of the new lumiescent powder not only has more color adjustability,but also has no color difference,so it has greater application potential in the preparation of photo-response fiber.