Study On Luminescence Properties And Anti-Counterfeiting Application Of Gallogermanate Long Persistent Materials

Long persistent materials are widely used in emergency lighting,optical storage,and biomedicine due to their special luminescent properties.Using long persistent luminescent materials to design anti-counterfeiting devices can effectively improve the shortcomings of traditional anti-counterfeiting technology,which has a low level of anti-counterfeiting and is easy to be copied on a large scale.The long persistent materials of gallate system and germanate system have attracted extensive attention due to their good chemical and physical stability,low synthesis temperature,and abundant traps.In this paper,two long persistent materials,gallate and germanate,were synthesized respectively.The structure and luminescence properties of the materials were characterized,and their application in the field of anti-counterfeiting was explored,which can effectively compensate for the traditional aluminum Acid and silicate-based long persistent materials have the defects of excessively high synthesis temperature.The main contents of this paper are as follows:1.A series of Sr₃Ga₄O₉:Bi³⁺long persistent materials were prepared by high temperature solid state method.The crystal structure and surface morphology of the materials were analyzed by XRD,SEM and EDS.Under the UV excitation of 250 nm,Bi³⁺ion-doped Sr₃Ga₄O₉has two asymmetric emission bands at 536 nm and 680 nm,which is attributed to the ³P₁→¹S₀transition of Bi³⁺ion.The afterglow decay curve and afterglow spectrum show that 7%of the Bi³⁺ion doping concentration has the best afterglow performance,and the afterglow time is more than 10 h.The filling and release process of carriers in the trap was analyzed by thermoluminescence（TL）.Since the carriers in the deep traps are more stable at room temperature,they have better afterglow performance at high temperatures.2.Design and synthesis of Sr₃Ga₄O₉long persistent materials doped with Tb³⁺ions.The crystal structure and surface morphology of the materials were analyzed by XRD,SEM and EDS.Under 250 nm excitation,there are three emission bands with different intensities between 500 nm and 650 nm,which are attributed to the ⁵D₄→⁷F₅,⁵D₄→⁷F₄and ⁵D₄→⁷F₃electronic transitions of Tb³⁺ions.The afterglow properties of phosphors were characterized by afterglow decay curve,afterglow spectrum and high temperature afterglow decay,respectively.The defect state structure of the sample analyzed by TL spectroscopy was measured,and the TL of Sr₃Ga₄O₉:5%Tb³⁺was fitted into two TL peaks with different depths by Gaussian fitting,indicating that there may be two traps with different depths in the sample.The trap depth is calculated using the formula,and the proper trap depth ensures the slow release of carriers.According to the different luminescence properties of Sr₃Ga₄O₉:Tb³⁺and Sr₃Ga₄O₉:Bi³⁺,a flexible anti-counterfeiting device with the word"HUNAU"was fabricated by combining the material with PDMS.The anti-counterfeiting can be detected by cheap portable ultraviolet lamp,which effectively improves the safety level of anti-counterfeiting technology.3.Mn²⁺ion and Sm³⁺ion doped Ca₄Zr Ge₃O₁₂long persistent materials were synthesized by high temperature solid state method.The crystal structure and surface morphology of the materials were analyzed by XRD,SEM and EDS.Under the excitation of 245 nm,the Ca₄Zr Ge₃O₁₂matrix has an emission band at 545 nm,which comes from the intrinsic defect of the matrix.The doping of Mn²⁺ions greatly improve the luminescence intensity,which is attributed to the⁴T₁→⁶A₁transition of Mn²⁺ions.After the doping of Sm³⁺ions,the excitation peak was red-shifted to 290nm,and a series of characteristic emission of Sm³⁺ions appeared.Under the excitation of 404 nm,the luminescence of Ca₄Zr Ge₃O₁₂matrix disappears,but the luminescence intensity of Sm³⁺ions increase obviously.The afterglow attenuation curve shows that 0.5%Mn²⁺ion doping concentration has the best afterglow performance,and the trap distribution of the sample analyzed by TL spectrum is measured.According to the unique luminescence characteristics of Ca₄Zr Ge₃O₁₂doped with Mn²⁺and Sm³⁺ions,a dual-mode luminescent anti-counterfeiting device was fabricated by combining the material with PDMS.It is proved that the long persistent materials Ca₄Zr Ge₃O₁₂:Mn²⁺and Ca₄Zr Ge₃O₁₂:Sm³⁺have potential application prospects in the field of luminous anti-counterfeiting.