Stable aqueous dispersions of fullerenes, C60 and C70, were prepared by simply injecting into water a saturated solution of fullerene in tetrahydofuran (THF), followed by THF removal by purging gaseous nitrogen. To our knowledge, this is the first report of the stable dispersion of C70 in water. Fullerenes are dispersed as monodisperse clusters in water, 60 nm in diameter. High resolution transmission electron microscopy revealed the polycrystalline nature of the cluster. The preparation of the dispersion is very easy to perform, and the dispersions thus obtained are of excellent colloidal stability even though no stabilizing agent is used. It was found that the surface of the cluster is negatively charged and the electrostatic repulsion between the negatively charged cluster surfaces is important for the stability of the dispersions.

Solution properties in water of hydrophobized pullulan containing 1.6 cholesterol groups per 100 glucose units (CHP-55-1.6) were studied by size exclusion column chromatography (SEC), dynamic (DLS) and static light scattering (SLS) methods, electron microscopy, lH NMR, and fluorescence spectroscopy.SEC measurementsshow that CHP (l.Omg/mL, 0.lOwt %) intermolecularly aggregates and providesrelatively monodispersive particles upon ultrasonication. Spherical particles with relatively uniform size (the diameter, 25 * 5 nm) were observed in the negatively stained electron microscopy of the aqueous CHP solution. The hydrodynamic radius of the CHP self-aggregate determined by DLS was approximately 13 nm, and the aggregation number determined by SLS was approximately 13; the weight averaged molecular weight of the self-aggregate was 7.6 X lo5, the root mean-square radius of gyration (Re) was 16.8 nm, and the second virial coefficient (Az) was 2.60 X 10-4 (mol mL)/g2. The critical concentration of the self-aggregate formation determined fluorometrically was 0.01 mg/mL. In addition, they showed no surface activity at all up to the concentration of 0.145 mg/mL. Existence of microdomains which consist of both the rigid core of hydrophobic cholesterol and the relatively hydrophilic polysaccharide shell was auggested on the basis of both the line broadening of the proton signal of the cholesterol moiety of CHP(8 = 0.6-2.4 ppm) in the 'H NMR spectrum and the incorporation of several hydrophobic fluorescent probes in the CHP self-aggregates. The CHP self-aggregates strongly complexed with hydrophobic and less hydrophilic fluorescent probes similarly to the case of cyclodextrin.

Various cholesterol-bearing pullulans (CHPs) with different molecular weights of the parent pullulan and degrees of substitution (DS) of the cholesteryl moiety were synthesized. The structural characteristics of CHPs in water were studied by static (SLS) and dynamic light scattering (DLS) and the fluorescence probe method. Irrespective of the molecular weight of the parent pullulan and the DS, all of CHPs provided unimodal and monodisperse self-aggregates in water. The size of the self-aggregate decreased with an increase in the DS of the cholesteryl moiety (hydrodynamic radius, 8.4−13.7 nm). However, the aggregation number of CHP in one nanoparticle was almost independent of the DS. The polysaccharide density within the self-aggregate (0.13−0.50 g/mL) was affected by both the molecular weight and the DS of CHPs. The mean aggregation number of the cholesteryl moiety (3.5−5.7), which was estimated by the fluorescence quenching method using pyrene and cetylpyridinium chloride, was almost same for all the CHP self-aggregates. The CHP self-aggregate is regarded as a hydrogel nanoparticle, in which pullulan chains are cross-linked noncovalently by associating cholesteryl moieties. The microenvironment inside or the structural characteristic of the self-aggregate was spectrometrically studied using a fluorescence probe, ANS. The characteristic temperature to cause a structural change of the nanoparticle (T*) decreased with an increase in the DS of CHP and the ionic strength of the medium. The thermoresponsiveness of the nanoparticle hydrogel is related to the partial dehydration of the hydrophobized pullulan upon heating.

Colloidal dispersions of C60 and C70 were prepared by simply mixing a fullerene solution in a good solvent with a poor polar organic solvent for fullerenes. The process was very easy and fast and the formation of particles with average diameter in the colloidal range was detected immediately after the components were mixed. The formation and the properties of the fullerene particles were studied mainly with dynamic light scattering and high-resolution transmission electron microscopy. The most interesting findings are the long-term colloid stability of the samples in the absence of any stabilizers, the relatively narrow size distribution, and the different average sizes of the particles formed by C60, C70, and their mixtures. The influence of various factors such as fullerene concentration, mixing procedure, solvent properties, and C60/C70 ratio was investigated. It is shown that the smaller particles are formed when the total fullerene concentration in the good solvent is decreased and that the fullerene particles have crystalline structure. The measured negative values for the electrophoretic mobility of the particles suggest that fullerene dispersions in polar organic solvents are stabilized by repulsive electrostatic interactions.

The study of extracellular DNA viral particles in the ocean is currently one of the most advanced fields of research in viral metagenomic analysis. However, even though the intracellular viruses of marine microorganisms might be the major source of extracellular virus particles in the ocean, the diversity of these intracellular viruses is not well understood. Here, our newly developed method, referred to herein as fragmented and primer ligated dsRNA sequencing (flds) version 2, identified considerable genetic diversity of marine RNA viruses in cell fractions obtained from surface seawater. The RNA virus community appears to cover genome sequences related to more than half of the established positive-sense ssRNA and dsRNA virus families, in addition to a number of unidentified viral lineages, and such diversity had not been previously observed in floating viral particles. In this study, more dsRNA viral contigs were detected in host cells than in extracellular viral particles. This illustrates the magnitude of the previously unknown marine RNA virus population in cell fractions, which has only been partially assessed by cellular metatranscriptomics and not by contemporary viral metagenomic studies. These results reveal the importance of studying cell fractions to illuminate the full spectrum of viral diversity on Earth.

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

The behaviour of cellulose was studied in water at high temperatures and high pressures by in situ high-resolution optical microscopy. It was found that crystalline cellulose underwent transformation to an amorphous state in hot and compressed water, which was followed by complete dissolution. The finding shows that the chemical stability of cellulose in hot and compressed water is determined by the unique properties of cellulose that arise from extensive networks of hydrogen bonds among the cellulose chains in the crystal. The implications of the observation for hydrothermal conversion of cellulose are discussed. PAPERwww.rsc.org/greenchem | Green Chemistry

Crystalline-to-amorphous transformation of cellulose in water, just like that for starch upon cooking called gelatinisation, is revealed at 320 degrees C and 25 MPa.