Synthesis and structural characterization of nano-carbon materials: Nano-diamond films, graphene, CNTs and their modifications, and carbon nano-horns

In the formation of SWCNT controlling of its diameter and chirality will be shown to be affected by controlling the size of the metal catalyst. The usual size of carbon nanohorn (CNH) particles is about 80 nm but its smaller size of less than 30nm is needed for a biomedical application purpose because of their permeation through biological cell membranes. The small CNHs have been successfully realized by optimizing parameters for the growth of CNHs. The success is attributed to understanding of the growth nature of carbon nano-horns in CO₂ laser ablation of a carbon rod. Our recent successes of two approaches in producing a large size graphene sheet by CVD method using a copper or aluminum substrate foils is achieved on the basis of trial by error. It is a worth mentioning that the one of method is achieved using micro-wave CVD technique which has been developed for the nanodiamond film growth at low temperature down to room temperature. The low temperature growth of graphene at typically less than 300 °C. In the last half part of the presentation will be concerned with structural characterization of nanocarbon materials using atom-resolution electron microscopes as well as other characterization methods of Raman, photoluminescence and optical absorption spectroscopy, etc The advantage of high resolution electron microscopy (HRTEM) over other techniques is to be able to characterize local atomic structures such as lattice defects and edge structures of nano materials which cannot be studied in conventional techniques. Another emphasis of HRTEM will be on dynamic observation of a reaction process which is not available for other high resolution probe microscope techniques such as STM. In terms of application of nano-carbon materials SWCNTs should be mentioned as an excellent TEM specimen support materials. The SWCNTs were found to protect specimens enclosed inside the central hollows of SWCNTs from the electron beam irradiation damage. For example- a retinal molecule which is a organic molecule and easily decomposed in the electron beam irradiation can well be held in the SWCNTs. Some examples of above mentioned observations will be demonstrated: some latest results on structural characterization of carbon nanotubes, graphene, and boron nitride thin films, including "monatomic carbon strings that have been successfully made and observed in our laboratory.