Structural Modification,Luminescent Enhancement And Latent Fingerprint Detection Uses Of Rare Earth Ions Doped Synthetic Mica

Synthetic mica is a kind of clay materials with a unique layered structure.It has the advantages of high thermal and chemical stability,and strong exchange performance of cations between layers.In recent years,it has attracted extensive attention of researchers.Studies have shown that the isomorphism of synthetic mica is very popular,and the properties of materials can be significantly improved by micro-modification to the original structural arrangement.In this paper,the fluorophlogopite luminescent materials doped with different rare earth ions(Sm³⁺,Eu³⁺,Ce³⁺and Tb³⁺)were synthesized by high-temperature solid-phase method.It was found that the luminescence of mica materials was still very weak even at the optimal doping concentration of rare earth ions.In order to improve the optical properties of mica materials,the structure of mica was modified by changing the interlayer cation species and the charge arrangement in the layers so that the luminescence properties of rare earth Sm³⁺and Eu³⁺were enhanced in mica materials;Additionally,the rare earth Ce³⁺and Tb³⁺were co-doped into the interlayer of mica to enhance the fluorescence intensity and quantum yield of rare earth Tb³⁺through the energy transfer between the rare earth ions.,For the first time,the rare earth ions doped mica-based luminescent materials were applied to the field of forensic science and the detection of latent fingerprints was realized.The structure,composition and optical properties of the samples were studied by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,energy dispersive X-ray spectrum,fluorescence spectrum,chromaticity coordinates,fluorescence decay curve and fluorescence quantum yield.The research results indicated that all synthetic mica materials had obvious lamellar structure,and the interlayer spacing of the structurally modified samples was decreased.The rare earth Sm³⁺and Eu³⁺doped mica materials showed the respective ⁴G_5/2→⁶H_7/2and ⁵D₀→⁷F₂characteristic red emission under the blue-violet and ultraviolet light,and the luminescence intensity was greatly enhanced after the structure modification,which was nearly 30-fold and 9-fold higher than the previous samples,respectively.The rare earth Tb³⁺doped mica materials showed the ⁵D₄→⁷F₅characteristic green emission of Tb³⁺under ultraviolet light.After the energy transfer from the rare earth Ce³⁺→Tb³⁺,the fluorescence intensity was nearly 16-fold enhanced,and the fluorescence quantum yield increased from31%to 78%.The unique layered structure of synthetic mica and the presence of fluoride ion in its components endow the material with strong adhesion and lipophilicity,enabling the samples to detect latent fingerprints on various substrates,and the 1～3 levels fingerprint details can be clearly displayed after the visualized fingerprint image is enlarged.The mica-based material with high luminescent intensity can be obtained through the structural modification of the host and the energy transfer between the rare earth ions.This realization of latent fingerprint detection opens up the new ideas for the application of novel synthetic mica material.