Investigation On The Properties Of Peryleneimide Derivatives And Preparation Of Electrochemiluminescence Immunosensors

Electrochemiluminescence（ECL）immunosensor is a new type of biosensor constructed by combining immunoassay technology with electrochemical sensing technology.Because of its good specificity,low background interference,high sensitivity,short time-consuming and low detection limit,it is widely used in disease diagnosis,food safety analysis,environmental monitoring and other fields.Using ECL immunosensors to detetct cancer markers will be helpful for cancer diagnosis and early treatment.The sensitivity and detection limit of ECL immunosensors are closely related to the ECL efficiency of luminophores as detection signal.Thus it is crucial to develop good luminophores for the construction of ECL immunosensors.In recent years,peryleneimide and its derivatives have been widely used in the construction of ECL immunosensors due to their largeπ-conjugated structures and excellent ECL properties.Some nanocarriers with high loading and excellent electron transfer such as graphene oxide,ordered mesoporous carbon and carbon nanotubes were also used to load luminophores and enhance ECL signal.Furthermore,the ECL immunosensors’performance was improved.The main content of this thesis is the study of the ECL properties of peryleneimide derivatives and the construction of ECL immunosensors using peryleneimide derivatives as luminophores.It mainly includes the following three parts:1.Study on the ECL properties of peryleneimide derivativesBased on N,N-2-（3-dimethylaminoethyl）-3,4,9,10-peryleneimide（PDI）molecules,we investigated the ECL property of 1,6,7,12-tetrachlorine substituent（1,6,7,12-tetrachloro-N,N-2-（3-dimethylaminoethyl）-3,4,9,10-peryleneimide（PDI-Cl₄））,N,N-2-（3-dimethylhydroxyethylaminoethyl）-3,4,9,10-peryleneimide（HDPDI）)and studied the influence of different substituents on the ECL property of peryleneimide derivatives.In the presence of co-reactant K₂S₂O₈,the PDI molecules could produce strong ECL at-0.25V with wavelength 730 nm,which was attributed to excited PDI dimers.Compared with the first electron redox peaks-0.307/-0.389 V and the three characteristic absorption peaks380 nm,470 nm,500 nm of PDI,that of PDI-Cl₄ was positively shifted to-0.214/-0.351 V and red-shifted to 440 nm,500 nm,530 nm.The results indicated the LUMO/HOMO gap of PDI-Cl₄decreased,which was because the electron-withdrawing substituents-Cl decreased theπelectron cloud density of perylene backbones.The decrease ofπelectron cloud density of perylene backbones weakened the intermolecularπstacking interaction.In addition,the substituents-Cl caused large steric effects and distorted the spatial structure of perylene backbone.The aforementioned two factors were not beneficial to the formation of excited dimers and resulted in the significant decrease of ECL of PDI-Cl₄.However,compared with PDI,the ECL properties of HDPDI were basically unchanged,which was due to the fact that the substituents at the amide end have little effect on the formation of excited-state dimers of peryleneimide derivatives.2.Construction of potential-resolved ratiometric immunosensors based on carbon nitride nanosheets and peryleneimide derivative double emittersIn this work,we reported a new pair of potential-resolved cathode luminophores N,N’-dimethyl-3,4,9,10-perylenedicarboximide（PDI-CH₃）and graphite-like carbon nitride（CNNS）nanosheets.PDI-CH₃ acted as quenchers and could largely quench the ECL of CNNS through competitive consumption of coreactant K₂S₂O₈ by PDI-CH₃and ECL resonance energy transfer（RET）from CNNS（donor）to PDI-CH₃（acceptor）.Furthermore,a sandwiched immunosensor for tumor marker carcinoembryonic antigen（CEA）detection was fabricated using CNNS as ECL platform and PDI-CH₃ as ECL label of sencondary antibody（Ab₂）.With the increase of the incubation concentration of CEA on the glassy carbon electrode,the loading of PDI-CH₃ on the electrode gradually increased,resulting in a gradual increase in the ECL intensity of PDI-CH₃ at-0.44 V,and a gradual decrease in the ECL intensity of CNNS at-1.2V.Taking the logarithm of the ratio of the ECL intensities at-0.44 V and-1.2 V as the detection signal of the sensor,the self-calibration of the two signals effectively reduces the occurrence probability of"false positives"and"false negatives"in actual detection.Due to the double quenching effect of PDI-CH₃ on CNNS,it is shown that ECL_PDI-CH3/ECL_CNNS has an ultrasensitive linear response to CEA in the voltage range of-1.2 V-0 V.The simple and efficient ECL ratiometric system designed in this work provided solid bases for the development of accurate assay in early cancer diagnosis and therapy.3.Preparation of nitrogen-doped ordered mesoporous carbon nanospheres/peryleneimide derivative compositesNitrogen-doped ordered mesoporous carbon nanospheres（NOMCN）was prepared and as nanocarrier to load peryleneimide derivative HDPDI.The ECL intensity of the nanocomposites was very weak.But the electrochemical signal of HDPDI in the composite was very strong,which indicates that the ordered mesoporous carbon nanospheres have been successfully combined with HDPDI molecules.However,the ECL of the nanocomposites of ordered mesoporous carbon nanospheres and HDPDI is weak,which may be due to the fact that the HDPDI molecules are loaded on the surface of the ordered mesoporous carbon nanospheres in the form of single molecules,which is not conducive to the ECL process.The formation of excited dimers makes the ECL intensity of the composites very weak.Transmission electron microscopy of the nanocomposites of ordered mesoporous carbon nanospheres/HDPDI indicated that only a few HDPDI aggregates existed on the surface of ordered mesoporous carbon nanospheres.This is consistent with the above ECL results.