Design And Fabrication Of Novel Photofunctional Materials Based On The Layered Scandium Hydroxides

Layered rare earth hydroxides（LRHs）are a new type of functional materials,which are composed of positively charged hydroxide laminates and interlayer anions with balanced charge.Combining the unique layered crystal structure with rich interlayer chemical behaviors（anion exchange and embedding）,the LRHs can be widely used in adsorption,catalysis,sensing and biomedicine aspects.To enlarge the application in the photofunctional fields,it has been aroused great interests in enhancing and improving the luminescence properties of LRHs（R=Gd,Y,Eu,Tb,Lu）.However,the layered scandium hydroxide（LSc H）was hardly reported.As the fourth period and groupⅢB element,scandium（Sc）had no 4f electrons,inert fluorescence and smaller radius than lanthanide elements.In this paper,a series of composite materials based on the LSc H were designed and fabricated by the hydrothermal method,and the Tb³⁺and Eu³⁺were doped as green and red luminescence activators,respectively.The structure,morphology and luminescent properties of the synthesized samples were studied in detail.To enhance the luminescence of Tb³⁺and Eu³⁺,on the one hand,the energy transfer between rare earth ions was realized by co-doping rare earth ions Ce³⁺,Tb³⁺(Ce³⁺as sensitizer)or Tb³⁺,Eu³⁺(Tb³⁺as sensitizer),which greatly promoted the luminescence intensity of Tb³⁺（green）and Eu³⁺（red）.The Ce³⁺and Tb³⁺co-doped LSc H sample with excellent luminescence performance was used for latent fingerprint identification,which clearly presented the visual image of latent fingerprint.On the other hand,the adjustable chemical composition of LSc H was used to change the interlayer anions,and the embedded organic anions could transfer energy to the activators Tb³⁺and Eu³⁺in the host layer,so that the fluorescence performance of the composite was improved.The used organic sensitizers included 4-biphenylacetic acid（BPA）,disodium terephthalate（TA）,phthalic acid disodium salt,trimesic acid,isophthalic acid,4-biphenylcarboxylic acid and 2-naphthoic acid.Among them,BPA and TA showed the optimal sensitization effect on Tb³⁺,which was about 100-fold stronger than the previous one.Moreover,the insertion of TA^2-significantly enhances the luminescence of Eu³⁺,which was about 600-fold in respect to the original one.The above composite materials with superior luminescent properties were peeled into nano-sheets for the research of optical function.The colloidal solution of LSc H:Tb co-intercalated with BPA^-and dodecyl sulfonate（DS^-）has high selectivity for metal Fe³⁺ion,thus a fluorescent sensor of detecting Fe³⁺has been constructed with a detection limit of 0.15μM,which has the potential to determine the micro content of Fe³⁺in actual samples.By changing the proportion of two colloidal solution of LSc H:Tb/Eu co-intercalated with TA^2-and DS^-,adjustable luminescence color could be achieved.Combining with agar powder,hydrogels with diverse shapes and multicolor photoluminescence behavior was prepared.In addition,three kinds of colloidal solution could be combined with polyvinyl alcohol to prepare flexible and transparent luminescent films.This work has designed and fabricated a series of LSc H composites with luminescent properties,which not only enriches the members of LRHs family,but also develops the application of LRHs materials in optical devices,and provides a good approach for the development of novel photofunctional materials.