Polymer-based Long Persistent Luminescence Materials:Design Synthesis And Anti-counterfeiting Application

Generally speaking,luminescent materials are divided into fluorescent materials and phosphorescent materials.It has drawn great attention due to its potential applications in display,photoelectric devices,information storage,anti-counterfeiting,biological imaging and chemical sensing,etc.Therefore,the preparation of noveland efficient fluorescent and phosphorescent materials has always been a research hotspot.Thesis is devoted to develop new functional fluorescent and long-persistent luminescence?LPL?materialsand explores their mechanisms and practical applications.Here,the main contents includs three parts:In the first part,to developnovel lanthanide metal-organic frameworks?Ln-MOFs?to rapidly and reliably differentiate both metal ions in solution and volatile organic compounds?VOCs?in vapor.Versatile Eu³⁺/Tb³⁺-MOFs were fabricated based on a flexible ligand.It is noteworthy that the film fabricated using bimetallic Eu_0.47Tb_0.63-MOF and polyvinyl alcohol?PVA?could serve as an easily and convenient luminescent platform for distinguishing different metal ions in aqueous solution and VOCs in vapor.The luminescent film exhibited outstanding fingerprint correlation between the metal ions/VOCs and the emission intensity ratio of Eu³⁺/Tb³⁺ions.Since the Ln-MOF film is stable and reliable,the approach could be a very promising strategy to explore luminescent platforms with practical applications.In addition,the bimetallic Ln-MOFs showed fast recognition of Fe³⁺ion in aqueous solution with a response time of less than 10s,and could effectively probe styrene vapor within 4 min under 97%quenching efficiency.The second part is based on the accidental discoveries in the first part.it is found that organic ligand G has special photophysical properties.At room temperature and atmospheric environment,G does not emit any fluorescence or phosphorescence?254 or365 nm excitation?,but when G is doped into amorphous polymer matrix PVA,the prepared G-PVA film exhibits obvious LPL after the excitation light source?254 nm?is turned off.More interestingly,the LPL properties of G-PVA films exhibit a strong dependence on ultraviolet irradiation.That is to say,the LPL properties of G-PVA films are significantly improved with the increase of UV 254 nm irradiation time.The luminescence intensity,phosphorescent lifetime and quantum yield of G-PVA films are increased from19.51 a.u.,0.28s and 2.85%to 315.47 a.u.,0.71s and 11.23%respectively,which are about16 times,2.5 times and 2.23 times,respectively.According to this interesting phenomenon,we have developed a new kind of green environment-friendly ink-free screen printing technology,which can be applied to anti-counterfeiting fields such as medicine,tobacco,alcohol,electronic products and so on.In the third part,to keep the main framework of G,that is,the triphosphate structure inside G molecule and the external benzoic acid unit remain unchanged,by adjusting the molecular structure?the type,location,number of substituents,etc.?,changing the substituents on the aromatic ring of benzoic acid unit,a total of 8 potential phosphor molecules of G6-G13 are designed and synthesized.Then the eight potential phosphors were doped into the PVA matrix in a certain proportion,and the films were evenly dispersed and taped.It was found that only G7 and G12 molecules were doped into the PVA matrix and LPL properties with obvious irradiation dependence was found.Later,we developed an ink-free printing technology for clearer anti-counterfeiting patterns,which can be used for advanced anti-counterfeiting of tickets,invoices,RMB,luxury goods,etc.