Study On The Functionalization Of Carbon Nanotubes And Their Assembly Using Dielectrophoresis

Due to their exceptional structural and electronic properties, carbon nanotubes (CNTs) have become a focus of physical,chemical, material and even biological fields.However, their extremely poor solubility in solvents and lack of functional groups have strongly limited the application of CNTs in many fields. In order to realize the many potential applications that CNTs can offer, the chemical functionalization of CNTs is of fundamental importance. Introduction of functional groups, such as carboxyl and amino groups, not only can improve CNTs dispersibility in various solvents, but also are useful for the further chemical link with other compounds. On the other hand, for some practical applications, it is necessary to manipulate and position CNTs into appropriate locations and desired formations. Dielectrophoresis (DEP) has been demonstrated to be a promising technique for mass-scale assembly of CNTs and manipulations. In this paper, in order to overcome the existed problems in this area, We have studied the chemical functionalization and multifunctionalization of CNTs and their dispersibility in various solvents. Different CNTs structures from arrays to networks were obtained via DEP assembly. The effects of the experimental parameters on assembled structures have been discussed.To obtain the multifunctionalized multi-walled carbon nanotubes (MWCNTs), carboxyl and amino groups have been introduced onto the surface of the MWCNTs by the mixed acid treatment and the diazonium reaction, respectively. The presence of multifunctionality groups on the MWCNTs has been characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric (TGA) analysis, Raman spectra, scanning electron microscopy (SEM) and energy dispersive X-ray spectrum (EDS). The multifunctionalized carbon nanotubes were further utilized to react with acetyl chloride and ethylenediamine (EDA). The formation of the amide bond in the grafting reaction has been confirmed by FT-IR spectroscopy. The result indicates that the further grafting is successful. DEP technique was used to assemble CNTs arrays and network between parallel electrodes with different gap sizes. Carboxylic-functionalized CNTs were prepared to carry out DEP experiment in terms of their good dispersion in N, N-dimethylformamide (DMF) without using any polluting surfactants. From the characterization of assembled structures and numerical simulations of the electric field, it is found that the dielectrophoretic nanotube-nanotube interactions play crucial roles in DEP assembly. The obtained results show that the dielectrophoretic force fields and the DEP interactions among CNTs vary with the length of CNTs relative to the size of the electrode gap, leading to the variation of the assembled structures. The results can help analyze the assembly of CNTs between the parallel electrodes.