Study Of The Novel Nanomaterials With Aggregation-Induced Emission And Its Electroluminescence Application

On the surface of the electrode,the conversion of electrochemical energy to light through an electrochemical reaction is known as electrogenerated chemiluminescence,also referred to as electrochemiluminescence（ECL）.When the excited states of the molecules formed in the reaction return back to the ground state,accompanied by luminescence.This process is triggered by applying a suitable potential on the electrode,and the intensity of the released light is measured by a photodetector.ECL combines the advantages of electrochemistry with adjustable potential and chemiluminescence with high sensitivity,and also has the merits such as without external light source,simple instrument,fast speed,low background signal,and wide linear range.Therefore,ECL has been widely used in the fields of environmental monitoring,bioanalysis,and clinical therapeutics.For the past ten years,the study on aggregation-induced luminescence（AIE）has attracted people’s great research interests,and AIE materials have developed into valuable functional materials.Combining it with ECL technology,it is easy to create synergies and further construct the ideal ECL sensing platform.Owing to the superiorities of metal-organic framework（MOF）such as simple synthesis,high porosity,large specific surface area,easily functionalized surface and adjustable structure,it has been widely used in the preparation of ECL sensors.Tetraphenyl ethylene（TPE）derivatives,acted as one kind of typical AIE molecule,possess the strong blue fluorescence in aggregated state,and high fluorescence quantum yield and simple synthesis steps,thus it would be a good choice to employ the TPE derivatives as ligand to synthesize MOF.In this work,we used the AIE molecule,1,1,2,2-tetra（4-carboxylbiphenyl）ethylene（H₄TCBPE）as the ligand to design and prepare a series of self-luminous MOF with different morphologies.They were served as ECL signal indicator,and based on the ECL resonance energy transfer（ECL-RET）mechanism,we have successfully prepared the quenched type of ECL sensor to detect different targets with high sensitivity and selectivity.The main contents of this paper are as follows:（1）Through the combination of aggregation-induced emission luminogens（AIEgens）,H₄TCBPE,with Zr（IV）cations,the dumbbell plate-shaped self-luminous MOF（Zr-TCBPE-MOF）was synthesized as the novel ECL tags.We found that Zr-TCBPE-MOF has the matrix coordination-induced ECL（MCI-ECL）enhancement effect.This phenomenon represents that the resultant MOF exhibited stronger ECL activity than those of H₄TCBPE monomers and aggregates.The strong ECL emission was not only because of the generated frameworks of MOFs that restricted the distorted relaxation,and thus blocked the non-radiative decay,but also due to the presence of abundant porous structure within MOF,which made both interior and surface H₄TCBPE ligands fully activated,realizing the intensive ECL emission.Subsequently,polyethyleneimine（PEI）as the coreactant was covalently connected with MOF,and the robust ECL signal of Zr-TCBPE-MOF was captured owing to the intramolecular-like coreaction acceleration.Based on the ECL-RET behavior,the Au Pd@Si O₂ composite was designed as the quencher,and an ultrasensitive ECL sensor was constructed for neuron-specific enolase（NSE）detection specifically through sandwich-type immunoreaction.Under optimal conditions,the ECL immunosensor for NSE detection exhibited a wide detection range from 0.0001 ng m L^-1 to 10 ng m L^-1,with the detection limit down to 52 fg m L^-1.The proposed sensing platform of this work exhibited the excellent potentiality for trace detection in bioanalysis.（2）By using H₄TCBPE as the ligand,it can coordinate with Zr Cl₄ to obtain a ellipsoidal MOF structure（Zr-TCBPE）assembled by two-dimensional nanosheets,and this Zr-TCBPE with high ECL emission efficiency was acted as the novel ECL luminophor.Afterwards,the composites of Fe-MOF@Pd NPs were synthesized as the peroxidase mimicase.At the same time,owing to the large specific surface area of Fe-MOF,it could load a large amount of Pd NPs and adsorb abundant second antibodies on its surface,thus improving the detection sensitivity.Based on the excellent ECL activity of Zr-TCBPE,as well as high catalytic activity and quenching properties of bifunctional Fe-MOF@Pd NPs complex,we designed one dual-mode biosensor with colorimetric and ECL for sensitive detection of cardiac troponin I（c Tn-I）.Under the optimal experimental conditions,the fabricated sensor was used to detect c Tn-I,with a detection linear range of 0.0002～50 ng m L^-1,and a detection limit of13.6 fg m L^-1.（3）Using H₄TCBPE as the ligand,we prepared one novel hexagonal prism-shaped MOF（Zr-MOF）,which was regarded as the ECL emitter.Furthermore,in the absence of coreactant,the obtained Zr-MOF exhibited efficient and stable ECL emission.In addition,because of the high affinity between Zr-MOF and the phosphate group,the target ATP was directly anchored on Zr-MOF through the coordination interaction.Then a new type nanocomposite of NH₂-Cu₂O@Pd was prepared and acted as effective ECL quencher.Based on ECL-RET mechanism,a novel ECL aptasensor was constructed for specific detection of ATP.With the optimized conditions,different concentrations of ATP solution were detected,and a wide linear range of 0.5～1500 nmol L^-1 was obtained,with the detection limit of 0.17 nmol L^-1.Moreover,the aptasensor has excellent stability,selectivity and reproducibility,which can provide certain theoretical guidance in developing the novel aptasensor for multiple targets analysis.（4）Based on one simple hydrothermal strategy,one kind of self-luminous Zr-TCBPE was developed by the use of H₄TCBPE as ligands and Zr（IV）as coordination nodes.Au NPs were further modified on its surface by in-situ reduction,and thus the composite of Zr-TCBPE@Au NPs was prepared and served as the ECL signal probe.Then plenty of ss DNA aptamer could be grafted on the surface of the composite via Au-S binding,thereby improving the sensitivity of the proposed sensor.Without the presence of coreactant,the ECL emission mechanism of Zr-TCBPE was studied through the tests under different conditions,such as p H,dissolved oxygen and so on,and the results showed that it could react with OH^-in the PBS solution.Besides,the quenching probe of Fe₃O₄@PDA@Pd/Pt complex was prepared,which was further modified with the Pb²⁺aptamer.In this way,a novel“off-on”type ECL aptasensor was constructed for specific Pb²⁺analysis,and the linear range was from0.01 nmol L^-1 to 500 nmol L^-1,with the detection limit of 0.0033 nmol L^-1.