Study On The Preparation Of The Modified Electrodes And Their Electrocatalysis Properties

The aim of this paper is to explore new materials for preparing the modifiedelectrode and improving the electron transfer rates and the selectivity betweenelectroactive substance and electrode. As-prepared modified electrode have beenempolyed to detect catecholamine compounds such as dopamine （DA） and ascorbicacid （AA） for obtaining a good selectivity, a high sensitivity, and low detection limitand good stability. The morphology, structure, properties and applications have beeninvestigated by FT-IR spectroscopy （FT-IR）, scanning electron microscopy （SEM）,transmission electron microscopy （TEM）, X-Ray Powder Diffraction （XRD）, N2adsorption–desorption isotherms, CHNS/O Analyze, X-ray photoelectronspectroscopy （XPS）, cyclic voltammetry （CV）, differential pulse voltammetrytechnique （DPV）. The main results and conclusions are summarized as follows:（1） Metal–Organic Frameworks functionalized with ferrocene and itselectrocatalytic propertiesFerrocene, as a small mediator, is the rich electronic systems substances, which canpromote activate reactant and electronic transfer rate during potential sweep, showgood thermal stability characteristics, high physiological function and electrocatalyticactivity. Metal–organic frameworks compounds combined with ferrocene couldenhance the stability to preparing dopamine electrochemical sensor. The experimentalresults indicate that the Fc@MOFs-5composite modified electrode has beenobviously decrease overpotentials and improved the sensitivity and the selectivityunder the optimum conditions. The Fc@MOFs-5modified electrode has enhanced theanodic current and reduced overpotential of DA dopamine oxidation with a detectionlimit of1.0×10^-7M （S/N=3） with the linear range of4-300μM. All the results showthat Fc@MOFs-5modified electrode has a good electrocatalytic activity towarddopamine oxidation in the presence of AA.（2） AgCl/Polyaniline hybrid materials for selective determination of dopamine byelectrochemical methodsA promising electrochemical sensor based on AgCl/PANI hybrid material has been developed. The organic/inorganic hybrid material has exhibited good electrocatalyticproperties by cyclic voltammetry measurement and differential pulse voltammetry.The oxidation overpotential of dopamine decreased dramatically, and the oxidationpeak current and electron transfer rate increased significantly at AgCl/PANI/GCEcompared to those obtained at PANI/GCE, AgCl/GCE and bare GCE, correspondingto the synergistic effect between PANI and inorganic particle AgCl. Under theoptimized conditions, the linear response in the concentration range of0.7to6.0μMfor the selective determination dopamine on the AgCl/PANI/GCE is obtained with adetection limit of5.4×10-8M （S/N=3） using differential pulse voltammetry. Theresults indicated that the modified electrode can be used to determine dopaminewithout the interference from ascorbic acid and ensure high sensitivity and goodselectivity.（3） N-doped carbon nanorods as the ultrasensitive electrochemical sensors for thedetermination of dopamineThe nitrogen-doped carbon nanorods （N-CNRs） are prepared by directcarbonization method using polyaniline nanorods as carbon precursor at600℃.Notably, the unique porous structure and the electron-enriched heteroatom N incarbon nanorods are helpful for quick mass transfer for the electrolyte and selectivedetermination in N-CNRs. The electrochemical behaviors of the N-CNRs-Nafionmodified electrode are evaluated in connection with the dopamine and the ascorbicacid by cyclic voltammetry and differential pulse voltammetry. Experimental resultsindicate that the N-CNRs modified electrode has improved current responses, fastelectron transfer kinetics and obvious decrease overpotentials. The linear responsesfor the selective determination dopamine in the presence of ascorbic acid is obtainedin the range from0.008to15.0μM with the detection limit of8.9×10-9M （S/N=3） bydifferential pulse voltammetry under the optimum conditions. Meanwhile, a peakseparation of234mV between AA and DA has been selectively distinguished DAselectively by using DPV. The N-CNRs-Nafion modified electrode exhibits a widelinear range, very low detection limit and anti-interference ability. Simultaneously, wehave proposed a reaction mechanism for the electrocalalytic kinetic process of the N-CNRs.