The Luminescence Properties Of BaGa₂Si₂O₈:Eu²⁺,Eu³⁺,Pr³⁺ And Its Multimodal Anti-counterfeiting Applications

Luminescent materials synthesized by doping inorganic materials with various rare earth ions have excellent luminescent properties.Based on this,inorganic luminescent materials can have potential applications in solid-state lighting,safety labeling,lasers,optical amplifiers,temperature sensors,solar cells,etc.Anti-counterfeiting is an important part of the fight against counterfeit products,which can prevent the risk of economic losses and protect people's health.Phosphor powder has a good development prospect in anti-counterfeiting technology.In this work,the luminescence properties of BaGa₂Si₂O₈:Eu²⁺at different reduction times and the luminescence mechanism and properties of the samples with co-doped ion pr were studied.With the increase of reduction time,Eu³⁺in the matrix is gradually reduced to Eu²⁺,so that the fluorescent powder has emitted light of various colors,and the co-doped ion Pr improves the luminescent performance of the fluorescent powder.According to the special luminous performance of fluorescent powder,we have designed a pattern with multi-mode anti-counterfeiting and information encryption under the stimulation of various light sources.BaGa₂Si₂O₈ matrix and its doped series samples were prepared by high-temperature solid-phase method.The matrix and Eu²⁺doped samples with different concentrations were subjected to structural analysis and XRD refining treatment.The samples are monoclinic,in which Ba and O form an octahedral structure,and the doped ion Eu replaces the lattice of Ba in the crystal.Through the calculation of the energy band and the diffuse reflectance spectrum,we analyzed that the band gap of the sample was 3.89 eV.Scanning electron microscope was used to measure the morphology and distribution of each element of the sample,and it was confirmed that the sample contains all the elements in the chemical formula.At the same time,it was proved by X-ray photoelectron spectroscopy that the sample contained Eu²⁺and Eu³⁺,and it increased with the reduction time The concentration of Eu²⁺is greater than the concentration of Eu³⁺.From the luminescence emission spectra of different Eu²⁺doping concentrations,the optimum doping concentration was determined to be 1.5%.The optimal excitation wavelength of the sample obtained from the excitation emission spectrum was 385 nm and the optimal emission wavelength was 470 nm.The emission spectra of the samples at different reduction times show that as the reduction time increases,the color of the sample can change from red to blue at 254 nm,and the color change is not obvious at 365 nm.At the same time,the thermoluminescence spectrum of the sample was tested.The sample has a strong shallow trap and a weak deep trap.The sample only needs to be irradiated at 365 nm for 60 s to fill the trap..In order to improve the persistent luminescence performance of the sample,we selected Pr³⁺for the BaGa₂Si₂O₈ matrix for co-doping experiments with Eu²⁺.Similarly,we analyzed the phase structure of the co-doped sample.The co-doped ion will not affect the structure of the sample.Through careful analysis of the co-doped sample,the co-doped ion Pr and Eu will replace the lattice of Ba.The elemental distribution of the samples was analyzed using a scanning electron microscope.The luminescence properties of the co-doped Pr³⁺ions at different concentrations were tested.The optimal Pr³⁺doping concentration was 1.1%.The excitation emission spectrum and persistent luminescence excitation emission spectrum of the co-doped samples were tested.The optimal excitation light wavelength for persistent luminescence was 385 nm,the optimal emission wavelength is 490 nm.The persistent luminescence time of the samples with optimal doping concentration can reach 16000s.The presence of co-doped ion Pr³⁺did not become a new light-emitting center,but only increased the number of trap levels in the sample,stored some electrons,and provided more electrons to the light-emitting center Eu²⁺.The optimal doped concentration sample BaGa₂Si₂O₈:1.5%Eu²⁺,1.1%Pr³⁺was measured for its thermoluminescence spectrum.The depths of the two traps were calculated and analyzed.340 K)has a depth range of 0.35 ev to 0.67 ev,and deep traps?448 K?have a depth range of 0.78 ev to 0.79 ev.Powder samples of BaGa₂Si₂O₈:1.5%Eu²⁺,1.1%Pr³⁺at different reduction times were prepared,and mixed with PDMS to make discs to test their photo-induced properties.It was found that the photo-induced properties were consistent with those of the single-doped samples at 254 nm.From red to blue,maintaining blue at 365 nm and persistent luminescence from colorless to blue.Using the light-emitting characteristics of samples with different light-emitting colors under different reduction times under different light sources,we have designed two anti-counterfeit patterns,which are Tai Chi and water fish.In addition,we have also designed two types of information encryption applications,which are password boxes and maze.