Electrochemiluminescence Of Quantum Dots Microspheres And Its Biosensing Applications

Electrochemiluminescence（ECL）is an analytical method which combines the advantages of electrochemistry and chemiluminescence.In recent years,quantum dots（QDs）as novel semiconductor nano materials,play an important role in optical,thermal,electrical and magnetic fields.QDs have many unique properties because of its particular quantum effect and excellent optical properties,such as wide and continuous excitation spectrum,tunable fluorescence emission wavelength,good optical stability and high quantum yield.In the past decade,more and more QDs have been proved to have excellent ECL properties,and the QDs-based ECL biosensors have also developed rapidly.However,the application of QDs,especially its ECL application,is still challenging,which mainly reflected in the following three aspects:（1）The ECL intensity of QDs is lower compared with traditional luminescent materials such as Ru（bpy）₃²⁺,which limits the sensitivity of QDs-based ECL sensors;（2）The influence of surface ligand changes on ECL of QDs has not been systematically studied;（3）The steps of ECL sensors are complex,which need to be simplified to save time and cost.Therefore,it is of great significance to enhance the ECL intensity of QDs and further reveal the ECL mechanism of QDs.The main content of this paper is the ECL of QDs.Firstly,the ECL properties and mechanism of QDs activated by N-（3-dimethylaminopropyl）-n’-ethylcarbodiimide（EDC）were investigated.Secondly,the ECL properties of PSQ/Fe₃O₄@Au NPs/QDs composites（PFQ）,which prepared by polysilsesquioxane microspheres（PSQ）,QDs and magnetic nano materials,have been researched.Then,a biosensor platform was constructed based on it.The content of this paper mainly includes the following two parts:1.Enhanced electrochemiluminescence of CdS quantum dots capped with mercaptopropionic acid activated by EDC and for Zika Virus detectionIn this study,the enhanced ECL signal of water-soluble CdS QDs capped with 3-mercaptopropionic acid（MPA@CdS QDs）has been reported after using EDC to activate the carboxyl groups.The ECL images of red and yellow activated MPA@CdS QDs can be taken directly with the mobile phone camera.Through a series of studies on its optical and ECL properties,the possible mechanism of ECL enhancement was proposed.A sandwich immunosensor for detecting Zika virus（ZIKV）antigen was fabricated based on CdS QDs as the signal labels and Si O₂ microspheres as the carrier.The proposed ECL immunosensor exhibited satisfactory sensitivity,selectivity and stability.The detection range was 1.0 fg·m L^-1-1.0 ng·m L^-1,and the detection limit was 0.3 fg·m L^-1.2.Signal-amplified electrochemiluminescence biosensor based on Zn CdSe/Zn S QDs aggregate as luminophorIn this experiment,firstly,PSQ,Fe₃O₄@Au NPs and PSQ/Fe₃O₄@Au/QDs（PFQ）composites were prepared.The ECL intensity of PFQ composite microspheres were stronger than Zn CdSe/Zn S QDs.The surface of PSQ microspheres modified with a large number of QDs and a suitable amount of Fe₃O₄@Au NPs.So that the ECL strength enhanced due to the aggregation of QDs.And the use of Fe₃O₄@Au NPs made it possible to quickly separate the target because of the paramagnetism of magnetic nanoparticles.On the other hand,Au NPs can connect antibodies well,which provides an effective protein connection site for the construction of biosensors.A series of methods,such as UV-vis spectrum,fluorescence spectrum,confocal microscope and fourier infrared spectrometer,were used to characterize the composite.The results showed that the PFQ composite was successfully prepared.The electrochemistry workstation was used to explore the ECL performance of PFQ.Finally,the magnetic fluorescent microspheres were used to label the antibody against carbohydrate antigen199（CA199）.Then,an ECL biosensor for the detection of CA199 was constructed.The detection range was 0.05-100 U·m L^-1,and the detection limit was 0.04 U·m L^-1.