Construction Of Electrochemical And Photoelectrochemical Sensors Based On Porous Framework Materials For The Detection Of C-reactive Protein And Heavy Metal Ion

Nanoporous materials,such as covalent organic frameworks?COFs?,metal-organic frameworks?MOFs?and organic polymer networks are extended highly ordered porous frameworks or networks,and which have already been widely applied in numerous fields,including biosensing,cancer diagnostics and therapy.Graphene and its structural similar materials,with the advantage of large surface area,good electrical conductivity,high mechanical strength and good biocompatibility,have attracted many researchers.In this thesis,a series of large specific surface area,high electron mobility and low cost,such as MoS₂-PANI nanocomposite,reduced graphene oxide,porphyrin-type covalent organic framework,nano-Cu?II?-HKUST-1,Pd/COF-LZU1,Pt/Ru/C nanocomposite,was synthesized and used to construct electrochemical and photoelectrochemical sensors for the detection of C-reactive protein and ions.?1?A rapid,ultrasensitive,and practical label-free electrochemical immunoassay for measuring Creactive protein in real serum samples was developed.The molybdenum disulfide-polyaniline-gold nanoparticles?MoS₂-PANI-Au NPs?with high conductivity were employed as the substrate to assist the electron transfer.Compared with bare electrode,about 10-fold increase in peak current could be detected for MoS₂-PANI-Au NPs.Moreover,MoS₂-PANI-Au NPs which have abundant adsorbing sites and large surface area could greatly increase loading amounts of antibodies,thus,significantly improve the performance of biosensing.Under the optimized experimental conditions,the proposed sensing strategy provides a linear dynamic range from 0.2 ng/mL-80 ng/mL and a detection limit of 40 pg/mL.The proposed immunosensor also has been used to determine CRP in human serum with satisfactory results.This possibly makes it an attractive platform in bioanalysis of proteins and other molecules.?2?In this chapter,Au nanoparticles?Au NPs?/reduced graphene oxide?RGO?was used as matrix of immunosensor to immobilize C-reactive protein?CRP?antibody on the surface of glassy carbon electrode.A sandwich immunosensor was constructed using quinone dicarboxylic acid as tag.Under the optimal experiment conditions,the concentration of CRP can be detected using differential pulse voltammetry.The linear range is 0.25 ng/mL-100 ng/mL with the detection limit of0.08 ng/mL and the linear correlation coefficient of 0.997.The sensor provides a new simple means for the determination of C-reactive protein.?3?The porphyrin-type covalent organic framework?COFs?was synthesized by using 5,0,15,20-tetrakis?4-aminophenyl?porphyrin as a monomer to prepare photoelectric aptasensor for the photoelectrochemistry?PEC?quantitative detection of C-reactive protein.The experimental results show that the porphyrin-type covalent organic framework has good photoelectrochemical response and stability.When it was combined with spherical nickel sulfide,better photoelectrochemical response can be obtained.Nano-silver?Ag NPs?were used as capture material of biological molecular and hydrogen peroxide was used as electron donor.Under the optimal conditions,the PEC aptasensor has linear response within 0.5 ng/mL-100 ng/mL with a detection limit of 0.1 ng/mL.The sensor provides a new quantitative assay for C-reactive protein.?4?Currently,environmental pollution by heavy metals is a global problem.Therefore,it is crucial to develop a simple,convenient and fast electrochemical sensor for detecting metal ions.Metal-organic frameworks?MOFs?,a new class of crystalline porous materials constructed by metal-containing nodes bonded to organic bridging ligands hold great potential as metal ion capture and displacement.The nano-Cu?II?-HKUST-1-modified glassy carbon electrodes?GCEs?were exploited as electrochemical sensors for the detection of toxic heavy metal ions(Cd²⁺and Pb²⁺),which showed superior performances for both individual as well as simultaneous detection.For individual detection of Pb²⁺and Cd²⁺,a linear response in ion concentration range of 0.01?mol/L-10?mol/L and 0.01?mol/L-5?mol/L,and detection limit of 2 nmol/L and 2 nmol/L,respectively,were observed.In the experiment,the current response of Pb²⁺and Cd²⁺were compared with Cu²⁺,respectively.The results showed the ratio of the response signal of Pb²⁺and Cd²⁺to the response signal of Cu²⁺havegood linear response in the range of 0.01?mol/L-100?mol/L(Pb²⁺)and 0.01?mol/L-10?mol/L(Cd²⁺).Moreover,the nano-Cu?II?-HKUST-1-modified GCEs is also show perspective applications in detection of metal ions in real sample,as illustrated in this study for human serum sample.?5?The colorimetric analytical strategies have attracted intensive interest.However,most of them own relatively low sensitivity,which limit their applications in clinic detection.Herein,a novel logic gate colorimetric strategy based on iodide catalyingoxdizing reaction of H₂O₂ to 3,3,5,5-tetramethylbenzidine?TMB?was developed for simple,low-cost,naked-eye detection and quantification of analytes.Iodide could catalyze H₂O₂ oxidizing colorless TMB to produce a blue product..We reported for the first time that the catalytic activity of iodide could be dramatically enhanced in the presence of nanoporous materials,which could be acted as an amplifier system because iodide could be chemically absorbed and anchored onto the surface of nanoporous materials.Our proposed strategy afforded with high sensitivity towards target H₂O₂,resulting in a detection limit of 1 nmol/L,which is about1000-fold lower than that of traditional colorimetric assays.Moreover,a gradual increase of colorimetric signals was detected when the concentration of the particles was enhanced.A nanoporous materials/iodide-responsive multivalued logic computing system including INHIBIT,AND and OR logic gates was also implemented,demonstrating much lower cost and easier to achieve compared with previous works.Such a colorimetric strategy provides a novel system for applications in the determination of low abundance target in complex biological samples.