Novel and Practical Separation Processes for Fullerenes, Carbon Nanotubes and Nanodiamonds

Abstract

Nanocarbons, defined as nanometer-sized carbon clusters including fullerenes, carbon nanotubes and nano diamonds, are one of the most fascinating materials known today. Applications for electronics and optics require controlled size and/or structure of these materials, because the physical properties are well known to closely cor relate with the structures. Therefore, separation methods of nanocarbons have been investigated, in particular practical processes applicable to large-scale separation. This review describes three novel and practical methods for separating fullerenes, carbon nanotubes and nanodiamonds, which have been developed in our group. In fullerene separation, a solution of fullerene mixture including C60, C70 and C＞70 was filtered through a thin layer of activated carbon to provide pure C60 and C70. Since this process is very useful, many patents were filed, and this technology was successfully transferred to a company. Circular single-walled carbon nanotubes were obtained in high purity by use of ultrasonic atomization. While this sonochemical process has been employed only for homogeneous systems such as concentration of aqueous ethanol, this is the first example to apply the sonoprocess to solid/liquid biphasic system. Separation of nanodiamond by centrifugation was effective to obtain single-digit nanometer size diamonds as small as 4 nm from nanodiamond powder with median size of 30 nm. This process was successfully applied to large-scale separation. Filtration, sonication and centrifuga tion are very fundamental experimental techniques which can be used for the separation of these three types of nanocarbons. Therefore, these processes are expected to be applied to the industrial scale production of nano carbons, which should reduce cost and increase availability.

Absorption spectra of nanodiamond aqueous dispersions by optical absorption and optoacoustic spectroscopies

“…Fractionation of NDs was investigated previously [ 25 , 26 , 29 , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , 76 ]. However, optical spectra of different fractions have not been considered in detail.…”

“…Ultracentrifugation is a commonly used method for ND fractioning, basically for improving the stability [ 35 , 37 , 38 ]. FTIR was used to demonstrate different surface compositions of fractions characterized by different particle sizes [ 35 ].…”

“…Additionally, the interest recently has been focused on ND fractionation as it may produce the materials with the minimum particle size [ 25 , 26 , 29 , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] ] and gives particles with defined aggregate sizes for various applications like film and gel production [ 15 ]. Previously, it was reported that ND fractions have different surface chemical composition [ 40 ]; FTIR and especially DLS [ 35 , 36 , 43 ] are commonly used methods for fraction characterization, but the absorption spectra were not considered in full.…”

Nanocarbons for the Development of Advanced Catalysts

“…With the diversity of their structure, these characteristic values can be achieved over an extremely wide range of conditions. For these reasons, they are extensively studied in applications going from photonics and optoelectronics to biotech and nanomedicine, advanced electrodes, and polymer composites. − ,, …”

Various surfactants for 0 – 3 dimensional nanocarbons: Separation, exfoliation and solubilization

“…1 from the viewpoint of their surface activation with various surfactants. Physisorption of aromatic compounds and chemisorption of polymers have been applied to nanocarbons on the purpose of separation, exfoliation and solubilization as summarized in Table 1 [10].…”