| Recently,long persistent luminescence materials have been widely used in the fields of luminescent coatings,optical information storage,and biological imaging.At present,the emission wavelength of long-persistence materials mainly focus on visible and near-infrared regions,but the studies in the ultraviolet light still significantly lag behind.In addition,various hypotheses on the mechanism of long afterglow have been proposed,but there is little consensus on the details of the PL mechanism.In view of the above problems,this paper aims to solve the following scientific problems:1)design and synthesis of ultraviolet afterglow materials,study their luminescence,afterglow characteristics and applications;2)propose the mechanism of ultraviolet afterglow.Firstly,the crystal material Cs2NaYF6:Pr3+was selected as the research object,aiming to utilize the structure of matrix material Cs2NaYF6 with wide band gap,and the strong 4f5d-4f transition characteristics of Pr3+ions.Samples were synthesized by traditional solid phase synthesis technology,it was found that Cs2NaYF6:Pr3+exhibited excellent UVC long afterglow performance after X-ray excitation.The initial afterglow power density exceeded 10 milliwatts per square meter,and the afterglow decay time was longer than two hours.Moreover,even if the afterglow decays to a level that is difficult to detect with a highly sensitive detector,the vast amount of energy stored in it can still be continuously released by means of heating,near-infrared light or visible light excitation.According to a large number of experiments and theoretical calculation,Cs2NaYF6:Pr3+was found to contain large amounts of anionic vacancy,causing this kind of defect mode structure appear large amounts of electronic capture traps.To maximize afterglow strength and prolong the afterglow time,the suitable trap depth can be achieved by regulating the defect type modulation.On the basis of this study,the luminescence mechanism of UVC long afterglow was proposed.In addition,the application of this UVC long afterglow material in sterilization was further demonstrated,and it was found the afterglow strength was strong enough to kill pseudomonas aeruginosa.The UVC long-afterglow material can be repeatedly excited by X-ray and near-infrared light,therefore it can further release its stored energy and has an important application prospect in cancer treatment.This work is the first systematic report on the design,preparation and application of UVC long afterglow materials,which provides an important research idea for the development of this kind of materials and opens up a new research direction for long afterglow materials.Secondly,in order to expand the research of ultraviolet afterglow materials,the design and characterization of UVA band afterglow materials were further carried out.By introducing Tb3+ions into the substrate material Cs2NaYF6,it was found that Cs2NaYF6:Tb3+exhibited ultra-strong UVA long afterglow properties after X-ray excitation,and the afterglow decay is more than 50 hours.Based on thermoluminescence data,the luminescence mechanism of UVA long afterglow was proposed.This work enriched the database of long-persistence luminescence materials greatly and improved the luminescence band of the materials.Based on the design and regulation of UVC and UVA long-persistence materials,people will have a better understanding to the material of Cs2NaYF6,an ancient and energetic luminous material. |
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