Fabrication Of One-dimensional Conducting Polymer-based Nanocomposites And Their Synergistic Enzyme-like Catalytic Properties

Enzyme catalytic reaction is an important part in the field of biological engineering,which has been already found to show wide applications in numerous fields,including food,textile,medicine,chemical industry and so on.It has the advantages of high catalytic efficiency,less dosage,reaction specificity,etc,but nature enzymes have some defects in the process of extraction,application and storage,such as high-cost of preparation and purification,poor stability,harsh requirements for catalytic environment and the difficulty of recycling.Therefore,artificial mimetic enzyme has emerged as the time require,it refers to the synthetic catalytic materials with similar functions to natural enzymes,which have the characteristics of simple preparation,low cost,good stability and convenient modification.The hotspot of artificial enzymes is nanozymes,which are nanomaterials with enzyme-like activity.In recently years,many nanomaterials such as Au nanoparticles,magnetic Fe₃O₄ nanoparticles,V₂O₅ nanowires,carbon nanotubes have been reported to exhibit excellent intrinsic enzyme-like catalytic properties,showing promising applications in the fields of molecular detection,biosensing,biological conservation,etc.However,the single-component materials are often difficult to meet the actual needs,they have the disadvantages of such as low catalytic activity,poor affinity and easily aggregation.Multi-component composite nanomaterials,which could combine the properties of different materials,have the ability to enhance the catalytic activity of nanozymes.Conducting polymer nanomaterials have excellent conductivity and charge transfer ability,which can accelerate the electron transfer and catalytic process.The composites of conductive polymers with other nanoenzyme materials not only optimize the dispersion and stability,but also produce synergistic effects,which enhance the catalytic performance of composite materials.In this thesis,the design and synthesis of one-dimensional conducting polymer-based nanocomposites,by using various synthetic methods,such as self-assembly polymerization,electrospinning method,in-situ polymerization,vapor phase polymerization have been demonstrated.The influences of composition and morphology of different materials on the enzyme-like catalytic properties were investigated,effects of conducting polymer on catalytic performance are investigated emphatically.Based on the enzyme-like properties,the sensitive detection of hydrogen peroxide,glutathione and ascorbic acid were further achieved,and the selectivity of the analytes was also studied.The details are shown as follows:1.Poly?3,4-ethylenedioxythiophene?-based composites:?1?We have demonstrated a one-step self-assembly redox polymerization approach for the fabrication of coaxial Te@PEDOT coaxial nanocables.Then,the Te@PEDOT coaxial nanocables have been converted to Pd@PEDOT coaxial nanocables via a galvanic replacement reaction.The as-prepared Pd@PEDOT coaxial nanocables showed an enhanced peroxidase-like catalytic activity than Pd black,which may result from the coaxial nanocable structure and the synergistic effect between Pd and PEDOT.The detection limit of H₂O₂ is 4.83?M.This material preliminarily verified the enzyme-like catalytic activity enhancement of the conductive polymer.?2?We have successfully fabricated CeO₂/Co₃O₄/PEDOT composite nanofibers using a strategy involving electrospinning,calcination and in situ polymerization.The obtained CeO₂/Co₃O₄/PEDOT nanocomposite was fully characterized and used as a catalyst for a peroxidase-like reaction.The as-prepared CeO₂/Co₃O₄/PEDOT composite nanofibers showed an enhanced peroxidase-like catalytic activity compared with CeO₂/Co₃O₄ composite nanofibers and individual Co₃O₄ and CeO₂ nanofibers.This characteristic results from the synergistic effect among the components in the composite nanofibers.Kinetic studies showed that the as-prepared nanocomposites have benign affinity to H₂O₂ and TMB,and the detection limit of H₂O₂ is 1.67?M.2.Polypyrrole-based composites:?1?We have prepared FeMnO₃@PPy nanotubes via an electrospinning technique,calcination process and vapor phase polymerization process.By adjusting the reaction time,we can precisely control the thickness of the PPy shell and the density of FeMnO₃ nanoparticles encapsulated within PPy nanotubes.When the the reaction time was 120 min,the FeMnO₃@PPy nanotubes showed a highest peroxidase-like catalytic activity among all the samples,which is five times as high as that of FeMnO₃ nanofibers,which should be attributed to the large surface area,low density,suitable void space to increase the interfacial sites and the synergistic effect between FeMnO₃ and PPy components.The prepared FeMnO₃@PPy nanotubes exhibited an excellent peroxidase-like catalytic activity,which provided a convenient colorimetric route for the sensitive detection of GSH with a low detection limit?36 nM?and high sensitivity.?2?First,we prepared the MoS₂ nanotubes via a hydrothermal reaction,then the MoS₂-PPy-Pd nanotubes were prepared through a one-pot redox polymerization on the surface of MoS₂.Compared to any two-component composite material,ternary MoS₂-PPy-Pd nanotubes showed better peroxidase-like catalytic activity.The detection limit for H₂O₂ is 2.51?M.Based on the intrinsic peroxidase-like property,L-cysteine could also be detected with a detection limit as low as 78 nM and excellent selectivity is achieved.3.Polyaniline-based composites:?1?We have synthesized polyaniline nanowires via a solution mixing polymerization method,then MnO₂ was grown on the surface with KMnO₄ as an oxidant.The as-prepared PANi-MnO₂ nanowires showed an enhanced oxidase-like catalytic activity than individual MnO₂,reflecting the synergetic enhanced effect of PANi.Based on the intrinsic oxidase-like property,SO₃^2-and AA could be detected,with the detection limit of 79 nM and 26 nM,respectively.In addition,the selectivity is excellent.The disadvantage is that the peroxidase-like property of PANi-MnO₂ is poor.?2?In order to improve the peroxidase-like properties of PANi-MnO₂,Pd particles are introduced via an electron transfer reduction.The PANi-MnO₂-Pd nanowires not only have excellent peroxidase-like property,but also preserve the oxidase-like property.The peroxidase-like catalytic activity is much better than Pd black,which is attributed to the synergistic effect of the PANi-MnO₂ nanowires.The detection limit of L-cysteine is 83 nM,and the detection of AA is 35 nM,indicating that the PANi-MnO₂-Pd nanowires are excellent dual-enzyme-like materials.?3?We have developed a simple one-step self-assembly strategy for the preparation of spindle-shaped Au/PANi nanorods.The effects of different content of APTES and HAuCl₄ on the morphology were investigated.Owing to the synergetic effect between Au nanoparticles and the PANi matrix,an enhanced peroxidase-like catalytic activity is observed from Au/PANi nanorods compared with individual Au nanospheres and PANI nanofibers alone.The as-prepared Au/PANi nanorices are proven to be efficient SERS substrates.By combining the catalytic reaction and SERS properties of the oxidized TMB molecules,a simple approach for the detection of H₂O₂ with high sensitivity has been developed.The detection limit could reach 10^-8 M,much better than the UV monitoring results,providing a new idea for the detection of H₂O₂ or other substrates.