Research On The Construction Of Luminescent Biochemical Sensing Interface And Signal Amplification Systems By Molybdenum/Cadmium-based Chalcogenide Quantum Dots

Due to the stable luminescence,easy surface modification,large specific surface area,good water solubility,and narrow and symmetrical emission spectrum,chalcogenide quantum dots（QDs）have incomparable advantages over traditional organic luminophores,resulting in the extensive application prospects in the field of photoluminescence/electroluminescent sensing.Biochemical hazards such as explosives and biotoxins have the characteristics of high toxicity and great harm.However,the existing optical sensors for detecting biochemical hazards still suffer from low sensitivity,narrow detection range and poor selectivity.Therefore,it is urgent to develop a detection method with high sensitivity and strong specificity.It is a new attempt to utilize the characteristics and advantages of chalcogenide QDs to construct luminescent biochemical sensing interfaces for ultrasensitive detection of biochemical hazards.At present,the preparation and functionalization of chalcogenide QDs with good biocompatibility,as well as the signal amplification systems of luminescent biochemical sensing interface constructed by the interaction between QDs and biological probes,nanocarriers,metal-organic frameworks and magnetic mesoporous materials,are still lack of in-depth research on the realization of trace detection of biochemical hazards.Herein,combined with the portable luminescent biochemical sensing detection platform,this work focuses on exploring the preparation of functional molybdenum/cadmium-based chalcogenide QDs,the construction methods of the luminescent biochemical sensing interfaces and the signal amplification systems,which lays a foundation for the on-site and rapid detection of biochemical hazards.The main contents of the research are as follows:（1）Construction of the fluorescent chemical sensor based on MoS₂ QDs for detection of FOX-7 and its mechanism researchWater-soluble molybdenum disulfide quantum dots（MoS₂ QDs）were prepared by hydrothermal method.Based on the quenching effect of 1,1-diamino-2,2-dinitroethylene（FOX-7）on the fluorescence of MoS₂ QDs,a novel strategy was proposed to detect FOX-7 by using MoS₂ QDs as fluorescent probes.The fluorescence signals of MoS₂ QDs decreased with the increase of FOX-7 concentrations in the linear ranges of 0.5-100μmol/L,with the limit of detection（LOD）of 0.19μmol/L.The method had good selectivity and stability,and can meet the analysis requirements of simulated water samples.The recovery range was 99.20%～104.00%.Utilizing Fourier transform infrared,UV-visible absorption,fluorescence lifetime tests,and Stern-Volmer equation,the fluorescence quenching mechanism of MoS₂ QDs was systematically investigated.It was confirmed that the fluorescence quenching mechanism was mainly inner filter effect.（2）Construction of the photoluminescence/electroluminescent signal amplification system based on CdSe/ZnS QDs for detection of ricinCdSe/ZnS core-shell quantum dots（CdSe/ZnS QDs）were prepared by the aqueous colloid synthesis method,and the effect of ZnS on the fluorescence properties of CdSe/ZnS QDs was explored.The obtained CdSe/ZnS QDs exhibited excellent properties of fluorescence and electroluminescence（ECL）.Using CdSe/ZnS QDs-labeled monoclonal antibody as the dual-signal probe,combined with the streptavidin-biotin signal amplification system,a dual-readout immunosensor was designed for sensitive detection of ricin.The biotinylated polyclonal antibody immobilized on streptavidin functionalized magnetic microspheres was used as the magnetic capture probe.This simplified the sample separation process and improved the sensitivity of the sensor.The signal of the dual-readout immunosensor was proportional to the concentration of ricin.The linear detection range of the fluorescence immunosensor was 0.1-100 ng/m L with the LOD of 81.7 pg/m L.And the linear detection range of the ECL immunosensor was 0.01-100 ng/m L with the LOD of 5.5 pg/m L.The immunosensor has good anti-interference ability and reproducibility,making it suitable for analyzing simulated samples in the environments such as water and soil.The recovery rate ranged from 91.6%to 109.6%.（3）Construction of an ECL signal amplification system based on DMSN@QDs and protein A for detecting SARS-Co V-2 nucleocapsid proteinA highly sensitive ECL immunosensor for detecting SARS-Co V-2 nucleocapsid protein（NP）was constructed based on CdSe/ZnS QDs-decorated dendritic mesoporous silica nanoparticles（DMSN@QDs）and protein A functionalized magnetic microspheres（PA/MMPs）.DMSN,a mesoporous material with large specific surface area,abundant radial pores,and high porosity,acted as nanocarriers for enriching QDs and hindering their aggregation.DMSN@QDs were obtained by electrostatic self-assembly method.Through characterization methods such as TEM and BET,it was found that CdSe/ZnS QDs were uniformly dispersed in the radial pores of DMSN.DMSN@QDs have a large surface area and can be coupled with more antibodies to further improve the sensitivity of the sensor.Protein A can be directed to bind the antibody to reduce steric hindrance and improve the capture efficiency and biological activity of the antibody.The ECL immunosensor was constructed by using PA/MMPs-coupled antibody Ab₁ and DMSN@QDs-labeled antibody Ab₂ as the magnetic capture probe and the signal probe,respectively.The proposed ECL immunosensor exhibited sensitive response to NP in a linear range of 0.005-50 ng/m L with the LOD of 3.33 pg/m L.The sensor had been successfully applied to detect NP in simulated human serum samples with recoveries ranging from 94.0%to 120%,indicating that the sensor had good anti-interference ability and practicability.（4）Construction of an ECL signal amplification system based on MIL-88@QDs and Fe₃O₄@SiO₂ for SEB detectionA self-enhanced ECL immunosensor was constructed for detecting staphylococcal enterotoxin B（SEB）by using a signal amplification strategy of NH₂-MIL-88（Fe）loaded with CdSe/ZnS QDs（MIL-88@QDs）.With a large specific surface area,MIL-88 serves as the nanocarrier to immobilize abundant QDs and antibodies.In addition,MIL-88 also serves as an efficient co-reaction accelerator,accelerating the electric reduction of K₂S₂O₈ to produce more SO₄^·-,thus enhancing ECL signal of the QDs/K₂S₂O₈ system.Compared with other co-reaction accelerators,MIL-88 can produce plentiful SO₄^·-through the recycling redox of Fe³⁺/Fe²⁺.The sandwich ECL immunosensor was constructed by utilizing Fe₃O₄@SiO₂-labeled capture antibody Ab₁ and MIL-88@QDs-labeled antibody Ab₂ as the signal probe and the magnetic capture probe,respectively.The proposed ECL immunosensor displayed good analytical performance for SEB with a linear detection range of 0.01-50 ng/m L,and the LOD was determined as 9.21 pg/m L.The immunosensor had good selectivity and reproducibility,which has been successfully applied to detect SEB in simulated samples with good recoveries of 95%-110.8%.（5）Construction of an ECL signal amplification system based on Fe Si DQDs and ZIF-8/Au for detection of abrinMagnetic dendritic mesoporous silica（Fe₃O₄@SiO₂@DMS）with core-shell-shell structure was prepared by using Fe₃O₄ as magnetic core,SiO₂ as the intermediate protective layer,and dendritic mesoporous silica（DMS）as the outer shell.The large radial pores and high porosity of Fe₃O₄@SiO₂@DMS can load more QDs and prevent the aggregation of QDs.Magnetic-luminescent multifunctional hybrid materials（Fe Si DQDs）were synthesized via embedding CdSe/ZnS QDs into the radial pores of Fe₃O₄@SiO₂@DMS.It was observed that ZIF-8/Au can quench the ECL signal of Fe Si DQDs,which may be due to the occurrence of resonance energy transfer,as well as the steric hindrance effect and the poor conductivity of ZIF-8/Au.Based on the principle,a“signal-off”ECL immunosensor was designed to realize the sensitive detection of abrin.ECL response signals of the immunosensor were proportional to abrin concentrations ranging from 0.0005 to 50 ng/m L with a detection limit of 0.26 pg/m L.The immunosensor exhibited good selectivity and reproducibility,which was successfully applied to the detection of abrin in simulated samples with recoveries of 96.7%-107.6%.