Preparation Of Graphene-Based Nanomaterials,self-Assembled Monolayers And Its Application In Electrochemical Sensing

Chemically modified electrode is an important area in the field of electrochemistry and electrochemical analysis.The electrode is modified by molecules,ions,atoms,polymers and so on,which has excellent chemical properties.The modified electrodes have a broad application prospects for the greatly increasing of the specific surface area,catalytic properties and active sites.In the work,the carboxyl functionalized graphene and the graphene quantum dots were immobilized to the glassy carbon electrode(GCE)through covalent self-assembled method,and the hydroxylamine hydrochloride was immobilized to the electrode through electrochemical polymerizating.The various modified electrodes were used for the determination of dopamine(DA),hydroxyl free radicals(·OH),paracetamol(PA)and phenols,respectively,which all display excellent performance.(1)The carboxyl functionalized graphene was immobilized to the glassy carbon electrode by self-assembled via ethylenediamine as an arm linker.The modified electrode was applied to the detection of·OH and PA,respectively.The morphologies and structures of the films were characterized by scanning electron microscopy(SEM),fourier transform infrared spectroscopy(FT-IR)and atomic force microscopy(AFM).Its electrochemical property was explored by cyclic voltammetry(CV),differential pulse voltammetry(DPV)and electrochemical impedance spectra(EIS).The results showed that the modified electrode has good conductivity and catalytic activity.Since the 4-hydroxybenzoic acid(4-HBA)can capture the·OH and have a unique product of 3,4-dihydroxybenzoic acid(3,4-DHBA),the·OH sensor was successfully constructed by detection the concentration of 3,4-DHBA.Eventually,the modified electrode displays a good linear range from 1 to 450?M and a low detection limit of 0.173?M(S/N=3)to the 3,4-DHBA.Finally,the sensing platform was successfully applied for detection·OH in water.What's more,the modified electrode also displays a linear range from 1 to 400?M and a detection limit of 0.173?M(S/N=3)to PA.The modified electrode also displays good selectivity and stability.(2)In this study,the graphene quantum dots(GQDs)were synthesized using citric acid by a convenient method,and then a stable GQDs modified electrode was constructed via covalent monolayers self-assembled method.The GQDs were bound with oxygen groups(hydroxyl,carboxyl),which were characterized by fluorescence spectroscopy and FT-IR spectroscopy.The GQDs with negative charge based on the oxygen groups on the surface,so the GQDs modified electrode can adsorb positively charged DA and reject the negatively chargeed AA and UA.Its electrochemical property of the modified electrode was explored carefully by CV and DPV.The results show that modified electrode presents good electrochemical redox behavior to DA and can be used for the determination of DA.Under the selected conditions,the oxidation peak currents in DPV show good linear relationship with DA concentration in the range from 1 to 150?M with the low detection limit of 0.115?M and the well sensitivity of 1306?A m M^-1cm^-2.The DA sensor also has well anti-interference property to some potential interfering substances such as AA,UA.In addition,it also displays well reproducibility and stability.(3)In this section,a polymer film was formed by electrochemical electrolytic depositioned hydroxylamine hydrochloride(HONH₃Cl)on glassy carbon electrode.The modified electrode was applied for the detection of phenolic isomers and paracetamol,respectively.The results show that the electrodeposition of hydroxylamine hydrochloride modified electrode has good electrical catalysis for hydroquinone isomers and the?E_pof oxidation peak of hydroquinone(HQ),catechol(CC)were large enough for distinguishing.Hence it can be used as electrochemical sensor for simultaneous determination HQ and CC.Under optimal conditions,the hydroxylamine hydrochloride modified electrode displays a linear range from 1 to 500?M to HQ and CC,while a detection limit of 0.016 and 0.034?M(S/N=3)for HQ and CC,respectively.This indicated that the modified electrode can be used for the simultaneous determination of low content of dihydroxybenzene isomers.Morever,the modified electrode also displays a linear range from 1 to 400?M and a detection limit of0.13?M to PA.