Facile Generation of Fullerene Nanoparticles by Hand‐Grinding

Abstract

When particles become smaller than 100 nm, they exhibit properties that are not observed for molecules or their bulk counterparts.[1] Such particles are building blocks for nanotechnology-derived applications such as single-electron devices, ultradense recording media, bioelectronic devices and sensors, bioimaging, optoelectronic devices, catalysis, and chemical sensors, as well as energy conversion and storage. [1,2] The obvious approach to prepare small particles is a top-down approach, in which bulk solid is reduced to small particles by mechanical forces. However, this approach only gives particles on the order of micrometers in size, and nanoparticles are not obtained unless very high energy is applied by a special device such as a high-energy ball mill. [3,4] Thus, nanoparticles are generally produced by bottom-up approaches, in which molecules are allowed to assemble into nanoparticles in solution or the gas phase through chemical reactions. [1,2] We have found that in the case of fullerene C 60 , nanoparticles including those as small as 20 nm are readily produced by hand-grinding the bulk solid in an agate mortar. In this communication, top-down preparation of C 60 nanoparticles and their structure and properties are reported. Figure 1 shows scanning electron microscopy (SEM) images of C 60 before and after hand-grinding. As-received C 60 particles have a faceted morphology and are approximately 100 lm in size (Fig. 1a). Hand-grinding reduced the particle size, as expected (Fig. 1c). Surprisingly, close examination revealed the presence of a significant amount of particles smaller than 100 nm in an agglomerated form (Fig. 1d). Examination by high-resolution transmission electron microscopy (HRTEM) (Figs. 1e,f) revealed nanoparticles, including ones as small as 20 nm (Fig. 1f) with distinct fringes. Lattice spacings calculated from Fourier-transform images agree with those of bulk crystals of C 60 , [5] indicating that these particles are pristine crystals of C 60 . Powder X-ray diffractograms of as-received and hand-ground C 60 also indicate that the crystalline structure remains unchanged after hand-grinding (Fig. 2). The results demonstrate the unusual property of solid C 60 to readily form nanoparticles; top-down preparation of nanoparticles is usually associated with changes in the crystalline structure, including amorphization, because of the high energy applied to the sample. [3] The mechanism resulting in the generation of the C 60 nanoparticles is not clear at present, but the unique properties of the C 60 crystals, such as fast isotropic rotation of the molecule [6] and low cohesive energy (1.6 eV), [7] likely play an important role.A highly turbid dispersion was formed as soon as handground C 60 (7 mg) was mixed with 5 mL of water containing COMMUNICATIONS

Investigation of the Characteristics of Thulium Doped Alumina Nanoparticles for Applications in Silica-Based Fibers

“…The second method to obtain nanosized particles is by sonication. Sonication uses sound energy with frequencies of more than 20 kHz to agitate particles inside a sample Deguchi et al (2006). It can help to produce even dispersion of nanoparticles in liquid and it is very useful especially when it is not possible to stir the sample.…”

In vivo toxicity of nano-C60 aggregates complex with atrazine to aquatic organisms

“…Reactive oxygen species are considered as a significant factor contributing to the toxicity of nC 60 [22][23][24]. On the contrary, some studies showed that nC 60 did not have potential toxicity [9,[25][26][27], and could even act as free radical scavenger [7]. Therefore, due to different prepared methods and organisms used, there is still no consensus until now in the literature regarding the toxicity of nC 60 .…”

“…However, water stable nano-aggregates of C 60 (termed nC 60 ) can be formed from pristine C 60 in certain conditions, for example, by solvent exchanging (such as tetrahydrofuran and toluene) [8], hand-grinding [9], and prelonged stirring in water [10]. As it may be a most environmentally relevant form of C 60 [11], nC 60 has recently caused much concern about its toxicity to humans and the environment, though its concentration is usually less than 10 mg/L in aquatic environment [12,13].…”

Characterisation and determination of fullerenes: A critical review

“…Several procedures were reported (Table 2), mostly involving the solubilisation in water by solvent exchange using different organic solvents (ethanol, toluene, THF and acetone) via sonication or mechanical stirring [6,8,[10][11][12][13][14][15]82] . Additionally, the direct solubilisation of C 60 in water was also reported via sonication [12] or extended stirring [13][14][15] . The preparation conditions vary from one study to another in terms of stirring rate, sonication power, time used for sonication and/or stirring, amount of organic solvent and the filtration step.…”

“…Despite the fact that fullerenes are very hydrophobic with very low solubility in water, around 8 ng L -1 for C 60 [5] , several methods have been developed to disperse these compounds in aqueous media [6][7][8][9][10][11][12][13] leading to the formation of stable colloidal aggregates (nC 60 ), a highly hydrophilic supramolecular complex consisting of С 60 enclosed into a hydrated shell containing 24 water molecules: C 60 @(H 2 O) 24 . The aqueous suspensions of nC 60 are amber coloured and are stable for months to years at very low ionic strength [14,15] .…”