Functional Design Of MOFs And Its Application In Electrochemical Sensing

Metal-organic frameworks(MOFs),formed by the coordination bond between metal ions and organic ligand.Because of its adjustable pore structure,larger specific surface area and open metal site,MOFs have been successful applied in the fields of gas adsorption and separation,drug transport,catalyst,supercontainer and other fields.However,the organic branches of MOFs are intricate,the transmission of electrons in the structure is limited,and the conductivity is poor,which limits its application in the field of sensors.Therefore,this paper presents functionalized MOFs to improve the performance of MOFs for electrochemical sensing research,which is mainly divided into the following three parts:Chapter 2 Amperometric determination of hydroquinone and catechol using a glassy carbon electrode modified with a porous carbon material doped with an iron speciesA porous carbon material doped with an iron species(Fe/PC)was prepared by carbonizing a mixture of zeolitic imidazolate framework-8 in the presence of iron(?)ions.The resulting material was characterized by X-ray diffraction,nitrogen adsorption isotherms,transmission electron microscopy,and by Raman and X-ray photoelectron spectroscopy.Fe/PC was the deposited on the surface of glassy carbon electrode(GCE)to obtain a sensor for amperometric determination of phenolic compounds.The unique catalytic activity,good electrical conductivity and hierarchical structure of the Fe/PC composite result in good electrooxidative activity towards hydroquinone(HQ;typically at 0.044 V)and catechol(CC;typically at 0.16 V).Under optimal conditions,the amperometric responses are linear in the range from 0.1 to 120.0 ?mol · L-1 for HQ,and from 1.0 to 120.0 ?mol · L-1 for CC.The respective detection limits are 14.0 nmol ? L-1 and 33.0 nmol · L-1,respectively.The sensor is highly selective against potential interferents and was successfully applied to the determination of HQ and CC contents in(spiked)water samples.Chapter 3 Synthesis of polymer-manganese(?)-metalloporphyrin framework electrode materials with enhanced electrochemical performance for nonenzymatic hydrogen peroxide biosensorManganese(?)-metalloporphyrin framework(PCN-222(Mn)possess attractive intrinsic peroxidase-like activity,which can efficiently catalyze the oxidation of 3,3,5,5-tetramethylbenzidine in the coexistence of hydrogen peroxide(H2O2).Using these findings,poly-glutamic acid coated manganese(?)-metalloporphyrin framework(PGA/PCN-222(Mn))hybrid composite was firstly synthesized and developed as a sensitive and robust electrochemical nonenzyme amperometric biosensor for H2O2 detection.The construction of the sensor begins with the cast of PCN-222(Mn)onto the glassy carbon electrode surface,and then covered with poly-glutamic acid by electropolymerization.Resulting from the synergetic effects between PCN-222(Mn)and PGA,this amperometric method enables the analysis of H2O2 with a lower detection limit that corresponds to 31.0 nmol · L-1 mol · L-1 over a wide range of 0.5 to 1010.0 ?mol · L-1.In addition,PGA/PCN-222(Mn)had long-term stability over a wide range of pH from 1.0 to 9.0 than free horseradish peroxidase(HRP)and can be used at least 50 cycles without any losing analytical performance.Further application of the present system for H2O2 detection has been successfully demonstrated in human serum.Results in this study imply that manganese(?)-metalloporphyrin framework is promising materials for the development of high-performance electrochemical nonenzyme biosensors.Chapter 4 Novel core-shell PPy@ZIF-8 structures for sensitive electrochemical sensing applicationNovel polypyrrole@zeolitic imidazolate framework-8(ZIF-8)core-shell composites with large surface area and high electrochemical activity were proposed via using polyvinylpyrrolidone(PVP)-functionalized polypyrrole microsphere(PPy)as a template to in situ growth of ZIF-8 on its surface.A sensitive and stable electrochemical sensor was constructed based on PPy@ZIF-8 as a sensing platform.The PPy@ZIF-8 modified sensor exhibited an excellent conductivity with a linear range between 0.01-150.0 ?mol · L-1 and a low detection limit of 7.0 nmol · L-1 for detecting of quercetin(QR).A satisfactory selectivity towards QR in the coexisting of interfering substances was observed.Furthermore,the trace amount of QR in human plasma samples was successfully recorded which makes it promising for developing an effective sensing platform for the potential applications in bioanalysis.