Single-walled Carbon Nanotube Purification And Optimization Of The Preparation And Raman Studies

Since single-walled carbon nanotubes (CNTs) were discovered, relevant researches are of increasing interest for their fascinating physical, thermal and electronic properties. And huge potential commercial applications have also received so much attention. The synthesis, purification and characterization of SWCNTs become the main studies on nano material.There are many techniques for nanotubes synthesis. The CVD method appears to be a promising technique since it has the potential for a large-scale synthesis of SWCNTs. Many impurities such as amorphous carbon, fullerenes, nanocrystalline graphites, and metals were introduced during the synthesis. The presence of impurities may significantly influence the properties of the CNTs and limit the application. So the purification and optimization of the synthesis become very important. Several attempts have been tried to purify the CNTs powders, such as selective oxidation processes, chemical-agent purification, filtration methods, or a combination of these methods. These techniques, however, are far from perfect.Raman spectroscopy can be used as one of powerful techniques for the study of SWCNTs. Informations such as the structural and physical properties of the SWCNTs can be abtained from Raman spectra.The followings are the main results abtained in this paper:1,Water-assisted highly efficient purification of single-walled carbon nanotubes. Transmission Electron Microscope images and Raman spectra analyses confirm that compared with other oxidation treatments, the water-assisted purification method is more efficient to eliminate the carbonaceous impurities, which are even contained within graphite shells, and release the wrapped metal particles at the same time. And then after acid treatment, the metal particles were almost removed and high purity CNTs were obtained.2,Growth of single-walled carbon nanotubes with flatted Raman D-band. The Scanning Electron Microscope images and Raman spectra analyses show that the sample synthesized with one-step method is much purer than that with the conventional method. And the introduction of water neither changes the diameter distribution nor causes destruction to the carbon nanotubes.3,Detection of Raman-D band of purified carbon nanotubes with high sensitivity by"sandwich"SERS system. Compared with the Raman spectrum, RBM and Raman-D band in SERS were enhanced significantly. The appearance of the Raman-D band reflected abundant information of carbonaceous impurities.