Ionthermal Preparation And Fluorescence Properties Of Ln(?)-naphthalene Diacid Complex Fluorescent Probe

Fluorescent sensors have been widely studied in terms of temperature,pH,metal ions,solvents or small molecules,because of their low cost,fast response,good portability,high sensitivity and high selectivity.The lanthanide MOFs(Ln-MOFs)have characterical emission with high color purity,which could be excellent candidates for fluorescent probes.The emission color of Ln-MOFs depends on the lanthanide ions,and the luminescence intensity is related to the lattice environment in which the lanthanide ions are located.Therefore,the organic linkers are very important for regulating the luminescence mechanism of Ln-MOFs.Herein,2,6-naphthalene dicarboxylic acid(H2NDC)with a rigidity,highly conjugated ?-electron and an aromatic structure was selected as an organic linker,LnCl3·6H2O as metal sources,and ionic liquid[PMI]I as reaction media.[PMI]I was subjected to ionothermal reactions to obtain 13 allomeric compounds[Ln(NDC)(H2O)Cl](Ln=Eu(1),Tb(2),Dy(3),Sm(4),Ce(5)),Pr(6),Nd(7),Gd(8),Ho(9),Er(10),Tm(11),Yb(12),Lu(13)).Among them,compound 1 emits red light under the excitation of ultraviolet light,which is attributed to the "antenna effect" of NDC2-ligand to Eu3+.Compounds 7 and 12 have near-infrared emissions.The emissions of the other compounds come from the intraligand charge transation.Referring to the preparation processes of compounds 1 and 2,Pyromellitic acid(H4BTeC)was added as a second ligand into the reactions of 1 and 2 to obtain two mixed-ligand containing single metallic fluorescent probes 14 and 15[Ln(NDC)(H2O)Cl]@(H4BTeC)(Ln=Eu(14)and Tb(15)),and one Eu/Tb co-doped[Eu0.0053Tb0.9947(NDC)(H2O)Cl]@(H4BTeC)(16).Three ligands of H2NDC,biphthalic acid(H2BPDC)and 1,4-benzenedicarboxylic acid(H2BDC)were used to synthesis three Eu/Tb co-doped compounds[Eu0.1Tb0.9(L)(H2O)Cl](L=NDC2-(17),BPDC2-(18),BDC2-(19)),aiming at the regulation of the ligand energy.This work presented the properties and applications of the above fluorescent probes.The single-luminescence center fluorescent probes were optimized to the ratiometric fluorescent probe with dual-liminance centers,whose applications cover temperature sensing and the detection of the small biomass molecule.The detailed research contents are as follows:1.The red fluorescence of compound 1 quenches depending on temperature:gradually decreases with increasing temperature,and it quenches completely when temperature reaches about 200?,but as the temperature returns back to room temperature,its fluorescence recovers completely.Therefore,1 can be used as an excellent temperature sensor.A high temperature resistant polymer material-polyether sulfone(PES)was mixed with 1 into 1@PES composite films,which was used as a temperature sensor in a designed temperature alarm device.2.The first excited triplet energy of H2NDC ligand is 20921 cm-1,therefore,it can't excit Tb3+ in compound 2,[Tb(NDC)(H2O)Cl],whose fluorescence is from NDC2-ligand.A small amount of H4BeTe with a higher energy of 22390 cm-1 was added to obtain compound 15 which exhibited a characteristic green light emission of Tb with BeTC4-as a sensitizer.The control of Eu3+:Tb3+ ratio led to a fluorescent probe[Eu0.0053Tb0.9947(NDC)(H2O)Cl]@(H4BTeC)(compound 16)emitting yellow fluorescence.Vitamin C(AA)displays a similar UV-visible absorption to as H2NDC and H4BTeC ligands.It is reasonably desirable to detect AA according to the detection principle of competitive absorption.16@PMMA composite film was prepared by using hydrophobic polymer material-polymethyl methacrylate(PMMA)and compound 16.16@PMMA shows the available detection to AA with a detection limit of 16 ?mol/L.3.Considering the ligand energy,Eu and Tb co-doped compounds 17-19 were respectively prepared with H2NDC,H2BPDC(22727 cm-1)and H2BDC(26178 cm-1),which have similar structure and energy level.Different detection methods of 2,6-Pyridinedicarboxylic acid(DPA)by 17-19 were achieved by regulating the ligand energy.To simplify the process of detecting DPA,we made 17/18/19@CA films,the detection limits of 17/18/19@CA to DPA were 1.15,2.18 and 130.54 ?mol/L,respectively.The detection limit of compound 17 was the best.Through the time resolution test and the actual sample test,it is proved that the three films exhibit the instantaneous completion to DPA detection and the applicability to the actual sample.It also provides a theoretical basis for the actual DPA detection by the films.