Preparation And Anti-fake Application Of Rare Earth Polychromatic Luminescent Composite Hydrogel

To relief economic losses and safety problems caused by counterfeit incidents,the development of new intelligent anti-counterfeiting materials is of great significance.Upconversion nanomaterials are widely used in anti-counterfeiting because of their strong photochemical stability,photobleaching resistance,adjustable color and intuitive effect.However,monochrome luminescent materials are less secure and easy to copy.And multi-color luminescence and multi-mode luminescence materials can effectively improve the security of anti-counterfeiting by combining complex or changeable colors with encryption means.In this paper,multi-color luminescence and multi-mode luminescence anti-counterfeiting materials are developed on the basis of rich luminescence colors.Four series of rare earth luminescent nanomaterials are designed and synthesized.Meanwhile,their structures,luminescence properties and processes are regulated,further used for anti-counterfeiting display.The main contents are as follows:（1）Na YF₄:Yb,Tm（Er）@Na YF₄:Yb,Er（Tm）series materials were synthesized by solvothermal method.Through the optical recombination between Er³⁺and Tm³⁺and the concentration regulation of Yb³⁺,high purity upconversion emission is realized.The internal structure and energy transfer mode of the materials were investigated and the mechanism of multi-color upconversion emission was explained.Subsequently,multi-color luminescent materials and hydrogels were combined to form imaging materials.The luminescent colors and shapes are arranged and combined to construct 3D optical anti-counterfeiting code.Combined with ASCII code,the storage and encryption of information were achieved by controlling the switch of 980nm excitation light.It provides new inspiration for the development of new multi-color anti-counterfeiting materials.（2）To improve the security of anti-counterfeiting,multi-mode luminous composite hydrogels were prepared by combining Stokes and anti-Stokes luminous modes.Li Gd F₄:Yb,Tm（Er）@Li Gd F₄:Ce,Mn nanoparticles were synthesized by solvothermal method.Through the construction of core-shell structure and the regulation of Mn²⁺concentration,the structure and luminescence mechanism of the material were explored.The series of nanomaterials achieve purple,green,blue（oleic acid phase）,green（water phase）and white（oleic acid phase）luminescence under the excitation light of 980 nm,254 nm and 365 nm,respectively.Subsequently,it is combined with hydrogel to form imaging anti-counterfeiting materials,integrated into AES algorithm and ASCII code,to achieve high level anti-counterfeiting applications.It provides inspiration for the development of multi-mode luminescence anti-counterfeiting materials.