Building Of Sensitive Voltammetric Sensors Based On Carbon Nanomaterials And Its Application

High sensitivity and good selectivity were long-time goal in electrochemical analysis.Chemically modified electrode(CMEs)has become an important tool to achieve the goal,which can modify electrodes by the surface functionalization,and selectively bond and accumulate analyte in the modification layer.Carbon nanotubes and graphene as representatives of 1 D and 2 D carbon nanomaterials have unique advantage in the construction process of CMEs.However,hydrophobic structure makes them tend to agglomerate irreversibly in many solvents,which hinders their further development as electrode modified materials.Meanwhile,surface morphology also has important influence on the electrochemical properties of carbon nanotubes and graphene.Fast electron transfer was achieved along the axis of carbon nanotubes,so the vertical ordered arrangement of carbon nanotubes on the electrode surface will be beneficial to enhance the ability of electrical conduction and further improve the sensitivity of CMEs.The functionalization of carbon nanotubes and graphene not only changes the surface morphology,but also improves their dispersibility and increases the electrochemical active site.According to the ideas,a series of voltammetric sensors based on carbon nanotubes and graphene were prepared by ultrasonic treatment,Langmuir-Blodgett technique,water bath method and hydrothermal method,which implemented the sensitive determination of some small organic molecules.The main research content is expressed as follows:1.PSS functionalized carbon nanotubes(PSS-MWCNTs)was prepared with easy non-covalent bonding method.The voltammetric sensor based on this nanocomposite was used to detect phentolamine mesilate.The electrochemical properties of phentolamine mesilate were investigated in detail for the first time and a reasonable reaction mechanism was proposed.The dispersibility of PSS-MWCNTs and p-MWCNTs was compared,and the voltammetric behavior of phentolamine mesilate at PSS-MWCNTs/GCE and p-MWCNTs/GCE was investigated.The results showed that the introduction of PSS improved the dispersibility of MWCNTs and increased the accumulation capability to phentolamine mesilate.Utilizing the linear sweep voltammetry,the electroanalytical method for determination of phentolamine mesilate was established and employed for determination of phentolamine mesilate in tablets.2.With the aid of LB technique and octadecylamine(ODA),we explored a new method of perpendicularly modified MWCNTs on glassy carbon electrode.Owe to electrostatic attraction,MWCNTs and ODA parallel enwound each other to form vertical dense structure.The process was characterized by π-A isotherms and SEM images.Fe(CN)63-/4-was selected as a probe and the influence of layer number on the charge transfer properties was investigated by cyclic voltammetry.Due to the excellent electrical properties of the vertically aligned MWCNTs,the sensitive electrochemical sensing for methylparaben was achieved.Meanwhile,cosmetic samples were analyzed using proposed method and the results obtained were well satisfactory.3.Based on the above idea,the ODA was replaced by the electrically conducting polyaniline(PANI)to construct the vertical MWCNTs LB film modified GCE(MWCNTs-PANI-LB/GCE).From the SEM images,it was clear that MWCNTs was vertically arrayed on the substrate surface with the aid of polyaniline.The electrochemical responses of daidzein at randomly MWCNTs film and vertical MWCNTs LB film was compared,and the results futher indicated the difference of electron transfer along different direction of MWCNTs.From the determining outcome of daidzein in the pueraria lobata and daidzein tablets,the proposed approach showed excellent stability and reproducibility as well as applicability.4.The graphene modified GCE(GR/GCE)was prepared by dropping GR suspension onto the GCE surface.Based on this sensor,the electrochemical property of hymecromone was investigated systematically for the first time.GR/GCE was found having sensitive voltammetric response for hymecromone,and the established method could achieve the fast and accurate determination of hymecromone in capsule.In addition,the voltammetric behavior hymecromone at GR/GCE and MWCNTs/GCE was compared,indicating the different electrochemical property of GR and MWCNTs.5.β-cyclodextrin(β-CD)was grafted on the surface of GR sheets by non-covalent bonding method.The structure and morphology of β-CD-GR was characterized by FTIR and SEM.A sensitive voltammetric sensor based on β-CD-GR modified GCE was constructed and used in establishing the first electroanalytical method for determination of astilbin.The proposed method was successfully applied in determination of astilbin in rhizoma smilacis glabrae.The results showed that the addition of β-CD effectively improved the dispersibility of GR and increased the accumulation capability of astilbin.6.A new graphene nanocomposite,CeO2-poly(diallyldimethylammonium chloride)-graphene(CeO2-PDDA-GR),was prepared by an one-pot hydrothermal method.Characterization was performed by TEM,UV-vis and XRD.The voltammetric sensor based on this nanocomposite showed strong accumulation ability and excellent voltammetric response for eriocitrin.The proposed analytical method was used in determination of eriocitrin in lemon sample with satisfactory results...