Application Of Modified Electrodes Basing On Carbon Nanocomposites In Determination Of Depside And Flavonoids Compounds

Chlorogenic acid is one of the depside generated by dihydroxycinnamic acid and quinic acid;morin hydrate and luteolin are typical flavonoids compounds.As bioactive substances,they are commonly contained in nature.It has been reported that depside and flavonoids compounds play an important role in anti-virus,anti-oxidation and free radical scavenging activity.However,it will cause some side-effects to consume overdose of chlorogenic acid（7mg/kg body weight）in food safety.To accurate,quick and sensitive detect these substances is of great importance in the filed of clinical diagnosis,food and drug monitoring.In this paper,carbon-based nanocomposites electrochemical sensors were constructed,and its application in the determination of depside and flavonoids compounds.The main points of this thesis are briefly summarized as follows:（1）A chlorogenic acid sensor based on a chitosan（CS）and multi-walled carbon nanotubes（MWCNTs）modified glassy carbon electrode（GCE）was fabricated by a layer-by-layer（LBL）self-assembly method.The prepared electrode exhibits eminently catalytical performance for chlorogenic redox reactions in comparison with a bare GCE.The proposed sensor is significantly sensitive for the detection of chlorogenic acid and appears wide linear detection ranges at low concentrations from 0.02 to 0.1μmol dm^-3 and at high concentrations from 0.1 to 225μmol dm^-3with the accumulation time of 80 s in pH 1.0phosphate buffer solution.The detection limit is estimated to be 0.0117μmol dm^-3（S/N=3）.Furthermore,the chlorogenic acid sensor exhibited excellent selectivity and stability and was utilized in practical applications,in particular,for the determination of human real samples（2）A facile and high-efficiency one-pot method was employed to synthesize the PEDT-Au/reduced graphene oxide（PEDT-Au/rGO）nanocomposites.The morphology and structure of as-prepared PEDT-Au/rGO nanocomposites were characterized by scanning electron microscope（SEM）,transmission electron microscope（TEM）and X-ray spectroscopy（EDS）,and its electrochemical characteristics were studied by EIS,CV and SWV.The effects of square wave voltammetry（SWV）parameters,accumulation time,accumulation potential and pH of the supporting electrolyte for morin were optimized.At the optimal experimental conditions,the PEDT-Au/rGO/GCE presented a high sensitivity of 0.0083μmol dm^-3 and a wide linear range from 1 to 150μmol dm^-3 toward morin oxidation.（3）We fabricated a sensitive electrochemical sensor based on multi-walled carbon nanotubes/PEDT-Au nanocomposites（MWCNTs/PEDT-Au）modified glassy carbon electrode（MWCNTs/PEDT-Au/GCE）for electrochemical determination of luteolin.The MWCNTs/PEDT-Au nanocomposites exhibited large specific surface area,excellent catalytic activities and conductive ability,which was combined the advantages of MWCNTs,PEDT and Au nanoparticles.At the optimal experimental conditions,the MWCNTs/PEDT-Au/GCE presented a high sensitivity of 0.00022μmol dm^-3（S/N=3,n=3）and a linear range from0.1¹5μmol dm^-3and 0.001⁰.1μmol dm^-33 with a satisfactory recovery in Maishu capsule.