Electrochemiluminescence Sensors Based On Conductive Polyindole And Its Application In The Detection Of Marine Heavy Metal Ion Pollutants

With the urbanization of coastal areas,a large amount of industrial and agricultural wastewater,waste and household refuse enter the sea,causing marine pollution.Heavy metals are extremely harmful marine environmental pollutants because of their wide sources and difficult degradation.Therefore,it is very important to develop efficient methods for heavy metal analysis.Electrochemiluminescence（ECL）has been widely applied in food safety detection,medical diagnosis,environmental monitoring and other fields due to its advantages of high sensitivity,low background signal and no need for light source.In recent years,in order to further improve the sensitivity and accuracy of ECL sensor for detecting trace analytes,people have been focusing on exploring and developing suitable luminescent materials,coreactants and signal amplification strategies to enhance ECL signal.Conductive polyindole has good conductivity,stable and reversible redox activity,and its introduction into ECL system can not only improve the electron transfer rate,but also improve the load capacity and stability of ECL materials.In this paper,the combination of ECL materials and co-reaction accelerator with conductive polyindole enhances the luminous efficiency and response signal of ECL materials,and improves the detection accuracy of the sensor.In order to overcome the problems of multiple interfering substances and strong background signals in complex environment,a variety of DNA-assisted signal amplification techniques have been introduced to achieve the rapid amplification of trace targets,amplify the ECL signal response of biosensors,and improve the detection sensitivity and selectivity of sensors.Specific research contents are as follows:1.Electrochemiluminescence sensor based on Ce₂Sn₂O₇/P5FIn nanocomposites and its application in Hg（II）detectionIn this work,a novel ECL sensor for Hg²⁺detection is constructed based on the synthesized cerium stannite/poly（5-aldehyde indole）（Ce₂Sn₂O₇/P5FIn）composite material and DNA signal amplification technique.Specifically,the combination of Ce₂Sn₂O₇and P5FIn improves the electrochemical reaction rate between Ce₂Sn₂O₇and the co-reactant,and significantly enhances the ECL signal.Moreover,the large specific surface area of Ce₂Sn₂O₇/P5FIn facilitates the effective fixation of hairpin DNA H1.The target Hg²⁺is bound to the DNA strand（m DNA）rich in thymine bases（T）by T-Hg²⁺-T.Subsequently,with the assistance of polymerase（phi29 DNA）and restriction endonuclease（Nt.Bbv CI）,strand displacement amplification（SDA）reaction is triggered to generate a large number of simulated target（MT）.Hairpin DNA H1captures MT,which then further triggers a hybridization chain reaction（HCR）to produce long strand DNA（ds DNA）rich in cytosine.Finally,a large amount of Ag（I）is introduced through C-Ag⁺-C,which is used as a co-reaction accelerator of Ce₂Sn₂O₇-K₂S₂O₈system to significantly enhance the ECL signal strength.Under optimal conditions,the constructed ECL sensor can detect Hg²⁺in a wide linear response range of 1.0 f M-100 n M,with a detection limit of 0.30 f M.In addition,the sensor also has high sensitivity and good applicability in the detection of seawater samples.2.“On-on-off”electrochemiluminescence biosensor for detection of Pb（II）based on P6ICA/Sn S₂nanocompositesAn“on-on-off”ECL sensor for Pb²⁺detection is fabricated using poly（6-carboxyinindole）/tin disulfide（P6ICA/Sn S₂）nanocomposite as a co-reaction accelerator,BN quantum dots（BNQD）as an emitter,and Pb²⁺-DNAzyme signal amplification technology.Firstly,P6ICA/Sn S₂can improve the electrochemical reaction rate between BNQD and K₂S₂O₈,and promote the formation of intermediate SO₄^·-,thereby improving the ECL intensity of BNQDs and enabling the sensor platform to have a higher original ECL response to achieve the initial signal“on”state.It provides a good foundation for constructing“on-off-on”type ECL sensor.The ECL-energy resonance transfer（RET）between Au NPs and BNQDs is used to“turn off”the initial signal.Finally,in the presence of Pb²⁺,DNAzyme recognizes Pb²⁺and triggers a cleavage reaction to the cleavage site.The Au NPs are removed from the electrode surface,restoring the ECL signal to the“on”state again.ECL-RET is used to quench the signal and Pb²⁺-DNAzyme is introduced to amplify the signal,which greatly improved the specificity and sensitivity of the sensor.The ECL sensor has excellent analytical detection capability for Pb²⁺,with a linear detection range of 1.0p M-10μM and a detection limit of 0.26 p M.At the same time,the ECL sensor also has good analytical ability in the detection of Pb²⁺in actual water samples,and also provides a new strategy for the development of other heavy metal ion detection methods.3.Sensitive electrochemiluminescence sensor for detection of Hg（II）based on self-enhanced Ru-QDs@Si O₂and P6ICA/Mo S₂nanocompositesIn this work,a simple sensitive ECL biosensor for Hg²⁺detection is developed based on the self-enhanced ECL luminator（Ru-QDs@Si O₂）and a novel co-reaction accelerator（P6ICA/Mo S₂）,combined with DNA signal amplification technology.The donor Cd S QDs and acceptor Ru（bpy）₃²⁺are co-encapsulated in Si O₂nanospheres to prepare Ru-QDs@Si O₂nanoparticles.Thus ECL-RET can occur inside Ru-QDs@Si O₂nanoparticles,shortening the electron transport path between donor and acceptor,and enhancing the ECL signal intensity.P6ICA/Mo S₂has excellent electrical conductivity and good hierarchical structure,so it can effectively promote the generation of coreactive free radicals,achieve ECL signal enhancement,and provide a good substrate for fixing c DNA.At the same time,the ECL signal is further amplified by introducing Exo III auxiliary target cycle.It simplifies the cumbersome and complex construction process of the sensor.The sensor has sensitive detection ability for Hg²⁺.Its linear range is 0.1 f M-100 n M,and the detection limit is 0.07 f M.In addition,the ECL sensor has been successfully used to detect Hg²⁺in seawater samples,and also provides an efficient method for the detection of other trace heavy metals.