The Construction And Analysis Application Of Electrochemical Sensor Based On Carbon Nanotubes Nanocomposites

Since1991, Iijima have found the carbon nanotubes (CNTs), it is widely used inthe electric analysis field because of their peculiar electrochemical performance andlarge specific surface area. In this paper, multi-wall carbon nanotubes (MWNTs) wereused as a substrate, were covalently functionalized, composited with goldnanoparticles to prepare CNTs-based composite materials, and calcinated with hightemperature to dope carbon nanotubes. A new type electrode modified with abovematerials were prepared and characterized by all kinds of characterization methods.The modified electrodes were applied to detect phenolic and construct biosensor. Themain points of the paper are summarized as follows:1. The preparation of functionalized carbon nanotubes: multiwalled carbonnanotubes (MWCNTs) were carboxylated by reacting with epichlorohydrin, then withiminodiacetic acid. The melamine and carbon nanotubes were mixed by ultrasound,calcinated with500℃, and maked the melamine doping on the surface of carbonnanotubes (NCNTs). Two kinds of functionalized carbon nanotubes have beeninvestigated by scanning electron microscopy (SEM), transmission electronmicroscopy (TEM), cyclic voltammetry, differential pulse voltammetry(DPV) andelectrochemical.2. The carboxyl of the multi-walled carbon nanotubes (MWCNTs) was modifiedby glassy carbon electrode (GC) surface that based on the electrostatic attraction effect,constructing the negative modified interface, and then adsorbed L-cysteine (L-Cys)through the peptides, what’s more, utilized mercaptan bond (-SH) of L-cysteinemolecules to adsorb gold nanoparticles (nano-Au) of forming S-Au bond. Usingadsorption method to immobilized hemoglobin (Hb) on the glassy carbon electrodesurface with modifying carbon nanotubes through carboxylation, which connected togold nanoparticles and L-cysteine, thereby fabricating stableHb/nano-Au/L-Cys/CNT-COOH/GC modified electrode. The electrochemicalbehaviors about the modified electrode was investigated by using cyclicvoltammetry, linear scanning voltammetry and difference pulse voltammetry inphosphate buffer solution (PBS). As a result, electrocatalytic oxidation of catechol atthe modified electrode led to the increase of reduction peak current obviously, and thetesting condition was also optimized. Compared with general electrodes, the detection limition of modified electrodes was lower, and the sensitivity of modified electrodeswas improved by catechol.3. This paper report a novel amperometric biosensor for glucose based on immo-bilization of a highly sensitive glucose oxidase by affinity interactions on metalchelatefunctionalized carbon nanotubes (CNTs) with iminodiacetic acid. The directelectrochemistry of GOx on metal chelate-functionalized CNTs was investigated. Thenew technique for immobilization is exploiting the affinity of Co(II) ions to thehistidine and cysteine moieties on the surface of. The direct electrochemistry ofimmobilized GOx revealed that the functionalized CNTs greatly improve the directelectron transfer between GOx and the surface of the electrode to give a pair ofwell-defined and almost reversible redox peaks and undergoes fast heterogeneouselectron transfer with a rate constant (ks) of0.59s~-1. The GOx immobilized in thisway fully retained its activity for the oxidation of glucose. The resulting biosensor iscapable of detecting glucose at levels as low as0.01mM, and has excellentoperational stability (with no decrease in the activity of enzyme over a10days period).The method of immobilizing GOx is easy and also provides a model technique forpotential use with other redox enzymes and proteins.4. Melamine heat treatment of carbon nanotubes(NCNTs) materials were preparedby calcining a chemical vapor deposition(CVD) and carbon nanotubes(CNTs) under anitrogen atmosphere at500℃after melamine ultrasonic mixing, andNafion-NCNTs/Au1modified electrodes that were characterized. The fabricatedelectrode showed excellent electrochemical catalytic activities to the oxidation ofcatechol(CT), resorcinol(RS) and hydroquinone(HQ). The modified electrode made itsuitable for simultaneous determination of these compounds in the0.1mol/Lphosphate buffer (PBS) solution(pH6.98).The calibration curves for CT, RS and HQwere obtained in the range of5×10~-6-4×10~-4,2×10~-5-4×10~-4and1×10~-5-3×10~-4mol/L,respectively. As well as the detection limits were6.67×10-8mol/L(CT, S/N=3),3.82×10~-8mol/L(RS, S/N=3),8.64×10~-8mol/L(HQ, S/N=3).