Research On Properties Of Rare Earth Doped Oxide Fluorescent Materials For Anti-counterfeiting

Rare earth doped inorganic fluorescent materials have been favored by researchers because of their excellent luminescence properties.At present,inorganic fluorescent materials have been widely used in optical amplifiers,solar cells,lasers,temperature sensors and anti-counterfeiting fields.Among them,anti-counterfeiting is a focus of society,because it is not only related to the security of public property,but also vital to social stability.To ensure the safety of information,the current popular anti-counterfeiting methods such as digital watermarking technology,commodity identification technology,radio frequency identification technology and other technologies have improved the process and identification means,which undoubtedly also enhances the difficulty for consumers to identify the authenticity.In comparison,rare earth doped fluorescent materials are simple to make,stable in chemical properties and easy to identify,so they have more prospects in the anti-counterfeiting field.However,the traditional static luminescence materials only have one single emission mode,which is easy to be imitated by illegal elements.Therefore,it is urgent to develop anti-counterfeiting schemes that are not subject to the emission mode or fluorescent materials that can achieve multi-mode emission.Considering the influence of the host on the fluorescent materials,in this work,we selected two different oxide matrices,tried to doped a variety of rare earth ions to develop novel fluorescent materials,and proposed different anti-counterfeiting schemes based on the luminescence characteristics of the materials.The specific work is as follows:（1）The phosphors Ba Ga₂Si₂O₈:Yb³⁺,Er³⁺/Ho³⁺have been developed by solid state method and realized red and green luminescence when they were excited by 980nm laser.Based on the structural characteristics of the host,the emission spectra and the energy level of doping ions,we have proposed the corresponding transition mechanism.By analyzing the luminescence behavior of Er³⁺under different temperatures,it was concluded that the materials exhibited excellent feedback performance to the temperature variation.Additionally,due to the existence of Yb³⁺-Yb³⁺dimers and the heating effect of laser,the material showed optical bistability behavior,which was rare in previous reports on fluorescent materials.Considering the single emission mode of these materials,the photonic barcodes based on emission spectrum have been proposed.This strategy is not limited by the luminescence mode and provides possibility for the advanced application of single mode static luminescence materials in the field of anti-counterfeiting field.（2）In this work,we have prepared a series of Er³⁺doped BGGO phosphors via solid-state reaction,which could respond to the excitation of 980,808 and 382 nm pumping sources and display outstanding temperature sensing performance.Moreover,the samples have achieved green emission with high purity under the 808 and 382 nm excitation.And the introduction of Tb³⁺enriched the luminescence mode of materials,enabling them to realize down-conversion luminescence and long persistent luminescence.Based on the unique luminescence properties of materials,we have designed the strategies of digital display and binary digital-ASCII multiplex code with muti-mode emission,which is expected to enhance the security performance significantly.