Optical Properties And Application Of Carbon Phosphorescence Film

As emerging optical carbon nanomaterial,carbon dots(CDs)have attracted extensive attention of researchers owing to their merits of adjustable luminescence,good biocompatibility,high stability and low biotoxicity.Based on the characteristics of CDs,it has a wide range of applications in photoelectric devices,bioimaging,lighting display,information encryption,etc.However,CDs exhibit phosphorescence properties in addition to fluorescence under UV-vis excitation,which makes them a more widely used class of luminescent nanomaterials.Unlike fluorescence,CDs phosphorescence has a long lifetime,large Stokes shift,low background fluorescence,and high sensitivity to the environment,making them ideal for a variety of different applications from fingerprinting and bioimaging to information encryption and anticounterfeiting.However,due to the low sensitivity of CDs phosphorescence to oxygen and its own stability,most phosphorescence is realized in solid-state,which has low efficiency,short lifetime and single color.Considering the application of highefficiency and long-lifetime CDs phosphorescence films in display lighting and other fields,and the application prospects of multi-color phosphorescence films in information storage and anti-counterfeiting fields.This research work mainly focuses on the preparation of high-efficiency and long-lifetime phosphorescence CDs,and the optical properties of the phosphorescence films;the realization principle and optical properties of multi-color phosphorescence films;The application of phosphorescent LED,phosphorescent 3D objects and optical signature were realized by using the phosphorescence film.The relevant research results are as follows:1.Study on optical properties of phosphorescent CDs and phosphorescence films.Employing solid-state heating,high-efficiency and long-lifetime phosphorescence CDs were prepared in one step on a large scale,and combined with polyvinyl alcohol(PVA)to prepare high-efficiency phosphorescence films for phosphorescent lightemitting diodes(LEDs).First,CDs with bright green phosphorescence were prepared by solid-state heating using a biuret as single precursor.The phosphorescence emission center is located at 510 nm,the photoluminescence(PL)quantum efficiency(QY)is46%,and the phosphorescence lifetime is 956 ms.Through the structural characterization of the CDs,it is found that the green phosphorescence originates from the combined effect of abundant C=O on the carbon core and the surface of the CDs.Based on high efficiency and long lifetime phosphorescent CDs,long lifetime phosphorescent film was prepared by combining with polyvinyl alcohol.PVA can isolate the effect of oxygen on phosphorescent emission,resulting in high stability of phosphorescent film which provided a good foundation for the application of phosphorescence film.2.Study on the optical properties of multi-color phosphorescence films.Herein,triplet excitons in CDs have been brightened by embedding the CDs into PVA films and flexible multi-color phosphorescence films are realized for the first time.First,blue and green CDs were prepared by hydrothermal method and microwave method,and combined with PVA to prepare blue phosphorescence film and green phosphorescence film,respectively.The phosphorescent emission centers of the films are at 435 nm and 505 nm,respectively.Then,through phosphorescence energy resonance transfer(PRET),using green CDs as donors and rhodamine B(Rh B)and rhodamine 6G(Rh 6G)as acceptors,yellow and orange phosphorescence films with phosphorescent emission were realized the centers are at 560 nm and 590 nm,respectively.The research shows that the hydrogen bonds in the PVA film brighten the triplet excitons in CDs,suppress the energy deactivation of the triplet state,and reduce the non-radiative transitions,resulting in strong phosphorescence emission.3.Application of CDs phosphorescence film.Phosphorescent LEDs have the effect of supplementing light when the naked eye changes from bright field to darkfield,reducing the stimulation of the naked eye caused by the change light and shade.Based on this,the long lifetime phosphorescence film prepared was applied to phosphorescent LED,indicating its potential application in lighting display.Due to the good stability,flexibility and mechanical properties of multi-color phosphorescence films,3D phosphorescent objects were prepared by multicolor phosphorescence films.Subsequently,in order to further broaden the application of phosphorescence films,the multi-color phosphorescence films ware further used for optical signatures,and the signature habits and signature speed of different signers were recorded through the change of phosphorescence intensity,thereby showing different optical electronic signatures,indicating its potential application in the field of electronic signatures.