Nanometrology Sees Progress in Synthesis, Optics, and Microscopy
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Nanometrology Sees Progress in Synthesis, Optics, and Microscopy The Second International Workshop on Metrology, Standardization and Industrial Quality of Nanotubes (MSIN08) took place on June 28, 2008, in Montpellier, France, as a satellite of the Ninth International Conference on the Science and Application of Nanotubes (NT08). The MSIN08 satellite conference built upon the foundation laid by the first workshop (the MSIN07, held in Rio de Janeiro, on June 22, 2007). Some findings related to the important challenges and fundamental characteristics of nanometrology, as discussed in the December 2007 issue of the MRS Bulletin, were revisited due to the large number of new attendees, but the focus was mostly directed toward improvements achieved in synthesis, optics, and microscopy during the past year. Besides the further development of analytical techniques for metrological studies of carbon nanotubes, also included in the program were the applications of carbon nanotubes as sensors for developing nanometrology and two presentations on the formal and legal aspects of standards. Recent developments occurring in the synthesis of single-walled carbon nanotubes (SWNTs) have been impressive. From one extreme, a scalable and flexible technique for sorting SWNTs by their physical and electronic structure has been achieved using density gradient ultracentrifugation (DGU) in aqueous solutions. From another extreme, industrial-scale mass production of high-purity SWNTs has been achieved to establish a carbon nanotube-based industry (10 tons/year promised for 2010). With well-established and well-characterized SWNT material, metrology can develop consistently, forming the basis for the transition from nanotube-based science to technology. Confirmation of the DGU sorting methods by various groups has already occurred and mass production techniques that would decrease the price of SWNTs by several orders of magnitude are now expected. The impressive development of SWNT synthesis could only have happened because of the equally impressive development of SWNT characterization techniques. Optical absorption and spectroscopies (mostly photoluminescence and Raman scattering), and high-resolution transmission electron microscopy have achieved the level of accuracy to characterize,
unequivocally, the SWNT structure [(n,m), tube type and handedness]. Combining different methods for (n,m) characterization has given strong support to the credibility of the methods. The metrology of carbon nanotubes is rapidly moving forward, now addressing length-dependent effects and defects. These issues are important for the development of readily available techniques for accurate (n,m) population analysis. Moreover, SWNTs are not only a prototype for the development of characterization protocols. Carbon nanotubes are also a material that can be used for the development of nanometrology tools. At the MSIN08, the successful developments of gas sensors and electromechanical devices were demonstrated. Besides being compact and potentially cheap, the gas
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