| Since the discovery of multiwalled carbon nanotubes(MWNTs)by Iijima and the related single walled carbon nanotubes(SWNTs)in 1993 carbon nanotubes have attracted enormous interest because of their unique structural,mechanical and electronic properties.Because of their extraordinary physical and mechanical properties such as nano-size,large surface area,good conductance and high mechanical strength,carbon nanotubes are attractive for a diverse range of applications in panel displays,quantum wires,and hydrogen storage.These properties include high chemical and thermal stability,and some tubes exhibiting metallic conductivity.The conductivity along with their small size has seen them touted as one of the key materials to be used as molecular wires in molecular electronics.Their small size and conductivity means they can also be regarded as the biosensor and supercapacitor.For some applications,it is highly desirable to prepare aligned carbon nanotubes so that the properties of individual nanotubes can be easily assessed and they can be incorporated effectively into devices.As electrode materials,carbon nanotubes possess many advantages,including their excellent electrical property,high chemical stability,strong mechanical strength, and large surface area.As a result,carbon nanotubes based electrodes have recently been used in biosensors,including enzymes and DNA biosensors.Aligned carbon nanotubes also been employed as electrode of immobilization of enzymes.CNTs have many advantages in electrochemical measurements,such as the large active surface at electrodes of small dimensions,the enhanced electron transfer or the oftenindicated electrocatalytic properties which highly enhanced the sensibility and stability of biosensors.Supercapacitors have many advantages compared to the secondary battery;for instance long cycle life,simple principle and mode of construction,short charging time,safety,and high power density.Carbon nanotubes(CNTs)have been demonstrated to be exciting new material for electrodes of electrochemical energy, due to special hollow-tube structure,nanometer dimensions and high spscific surface area.The new applications of CNTs in the construction of biosensor and supercapacitor were presented in this paper:Chapter 1 The reviewThe discovery,the synthesis methods,the structure,and the category,especially the marvelous properties of CNTs were presented.On the bases of the principles of biosensors(including DNA biosensors and glucose biosensors)and supercapacitors, the applications of CNTs in above areas were reviewed.Chapter 2 Glucose biosensor based on Pt nanoparticles and glucose oxidase on aligned carbon nanotubes electrodeA sensitive amperometric glucose biosensor based on Platinum(Pt)nanoparticles modified aligned carbon nanotubes(ACNTs)electrode was investigated.Pt nanoparticles which could enhance the electrocatalytic activity of the electrode for electrooxidating hydrogen peroxide produced by enzymatic reactions were electrocrystallized on 4-aminobenzene monolayer-grafted aligned carbon nanotubes electrode by a potential-step method.These Pt nanoparticles modified ACNTs surfaces were characterized by scanning electron microscopy(SEM)and Transmission electron microscopy(TEM).The nano-scale Pt particles dispersed highly on ACNTs can be obtained.The enzyme electrode exhibits excellent response performance to glucose with linear range from 1×10-5-7×10-3mol/L and fast response time within 5s.Furthermore,this glucose biosensor also has good reproducibility.It is demonstrated that the Pt-ACNTs electrode with high electro-catalitic activity is a suitable basic electrode for preparing enzyme electrodes.Chapter 3 Electrochemical Detection of DNA Bybridization Using Nile Blue and Au Nanoparticles Supported on Carbon Nanotubes Modified ElectrodeDue to the good catalytic activity of gold(Au)nanoparticles to the electrochemistry hybridizing indicator Nile Blue(NB)and the good charge transport characteristic of carbon nanotubes,a novel and sensitive electrochemical DNA biosensor is described.First,synthesized the Au nanoparticles with the diameter of 16nm and mixed it with the carboxylic carbon nanotubes in Nafion solution. Oligonucleotide probes with amido group at the 5' end were attached onto the carboxyl supported on carbon nanotubes.Nile blue(NB)is the hybridizing indicator and the experimental parameter of NB was detected.The complementary DNA detection sensitivity was dramatically increased.Chapter 4 Characterizations of Supercapacitors on Aligned carbon nanotubes Electrochemically-grafted Polypyrrole nanocomposite electrodesTwo kinds of modalities of nanocomposite materials,polypyrrole modified aligned carbon nanotubes(PPy-ACNTs),have been synthesized by electrochemical method for supercapacitors.Results showed that the modality of the polyprrole film shell was controlled by the electropolymer scan time,from thin linear structure to thick spherical structure.The polypyrrole images on the surface of ACNTs were observed by scanning electron microscopy and field-emission scanning electron microscope. Contributed to PPy film as the shell and aligned carbon nanotubes as the core,such prepared composite displayed supercapacitance.Electrochemical techniques,including cyclic voltammetry,galvanostatic charge-discharge,and electrochemical impedance spectroscopy,were carried to measure the electrochemical properties of these composite,especially for its capacitance value.The capacitance of spherical and linear PPy-ACNTs electrodes electrode in 1.0M KCl significantly increased compared to that pure ACNTs due to the high surface roughness of polypyrrole-conducting polymer on the surface combined with high electrical conductivity and great surface area of ACNTs.It is demonstrated that the PPy-ACNTs nanocomposit materials have excellent capacitive response.
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