Preparing samples for fullerene C60 hazard tests: Stable dispersion of fullerene crystals in water using a bead mill

A dispersion method using a bead mill was developed for preparing suspensions used in hazard testing of nanosize fullerenes. Fullerene crystals (C₆₀) of several μm to 100 μm in size were wet ground using a bead mill and dispersed in pure water containing Tween 80 as a dispersant. The particle size, dispersing condition, crystallization and fullerene oxide in the suspension prepared by bead milling were evaluated. As a result, the conditions of bead milling where the sizes of fullerene crystals were reduced to 100 nm or less were found, which made it possible to prepare a fullerene aqueous dispersion system using Tween 80. Furthermore, by centrifugation, it became possible to prepare fullerene suspensions in which the particle size of the majority of the suspended particles was 100 nm or less. The prepared suspensions remained stable for almost two months. Controlling milling conditions and milling time made it possible to achieve dispersion while maintaining the crystallized state of the fullerenes, and operating in anaerobic conditions under shade effectively suppressed the production of oxidized fullerenes. The fullerene suspensions prepared by bead milling and centrifugation were suitable for endotracheal administration tests and inhalation tests using rats.     

Reducing HAuCl(4) by the C(60) dianion: C(60)-directed self-assembly of gold nanoparticles into novel fullerene bound gold nanoassemblies

The C(60) dianion is used to reduce tetrachloroauric acid (HAuCl(4)) for the first time; three-dimensional C(60) bound gold (Au-C(60)) nanoclusters are obtained from C(60)-directed self-assembly of gold nanoparticles due to the strong affinities of Au-C(60) and C(60)-C(60). The?process was monitored in situ by UV-vis-NIR spectroscopy. The resulting Au-C(60) nanoclusters were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive spectroscopy (EDS), x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and FT-IR and Raman spectroscopies. TEM demonstrates the formation of 3D nanonetwork aggregates, which are composed of discrete gold nanocores covered with a C(60) monolayer. The SAED and XRD patterns indicate that the gold nanocores inside the capped C(60) molecules belong to the face-centred cubic crystal structure, while the C(60) molecules are amorphous. The EDS and XPS measurements validate that the Au-C(60) nanoclusters contain only Au and C elements and Au(3+) is reduced to Au(0). FT-IR spectroscopy shows the chemiadsorption of C(60) to the gold nanocores, while Raman spectroscopy demonstrates the electron transfer from the gold nanocores to the chemiadsorbed C(60) molecules. Au-C(60) nanoclusters embedded in tetraoctyl-n-ammonium bromide (TOAB) on glassy carbon electrodes (GCEs) have been fabricated and have shown stable and well-defined electrochemical responses in aqueous solution.     

C60 fullerene promotes lung monolayer collapse

Airborne nanometre-sized pollutants are responsible for various respiratory diseases. Such pollutants can reach the gas-exchange surface in the alveoli, which is lined with a monolayer of lung surfactant. The relationship between physiological effects of pollutants and molecular-level interactions is largely unknown. Here, we determine the effects of carbon nanoparticles on the properties of a model of lung monolayer using molecular simulations. We simulate phase-separated lipid monolayers in the presence of a model pollutant nanoparticle, C₆₀ fullerene. In the absence of nanoparticles, the monolayers collapse only at very low surface tensions (around 0 mN m⁻¹). In the presence of nanoparticles, instead, monolayer collapse is observed at significantly higher surface tensions (up to ca 10 mN m⁻¹). Collapse at higher tensions is related to lower mechanical rigidity of the monolayer. It is possible that similar mechanisms operate on lung surfactant in vivo, which suggests that health effects of airborne carbon nanoparticles may be mediated by alterations of the mechanical properties of lung surfactant.     

C60、M@C60(M=Si,Ge)富勒烯分子的压缩力学特性

采用基于Tersoff势的分子动力学方法,模拟了温度T=300、700和1100K下C60、M@C60(M=Si,Ge)富勒烯分子的对径压缩过程。根据模拟结果,讨论了温度丁对3种富勒烯分子压缩力学特性的影响以及它们压缩力学特性的差异。研究表明,在300～1100K范围内,温度丁对C60、M@C60(M=Si,Ge)分子压缩力学特性无显著影响;当压缩应变至8％～16％左右,各富勒烯分子在加载点处开始“塌陷”,当压缩应变至28％～32％左右,各富勒烯达到承载极限;C60、Si@C60、Ge@C60分子依次具有由低到高的承载能力。     

Charge-transfer interaction between C60 fullerene and alkylnaphthalenes

A series of alkylnaphthalenes, namely 1,4-dimethylnaphthalene, 2,6-diethylnaphthalene, 2-ethylnaphthalene and pure naphthalene are not able to form Diels-Alder adducts with C₆₀ fullerene but produce a series of 1:1 charge-transfer complexes (CTC) where the aromatic compounds act as donor and C₆₀ as acceptor. The spectrophotometric analysis of these CTC has permitted to determine the equilibrium constants of the CTC formation at four different temperatures and the relative enthalpies and entropies of formation. The C₆₀-alkylnaphthalenes and C₆₀-naphthalene were identified as weakly bound CTC. Using the Mulliken theory of the CTC also the degree of charge transfer α was determined, confirming the results already suggested by the equilibrium constants, i.e., the weakly interaction between the donor and the acceptor considered.     

Electronic structure and electrical transport characteristics of C60, 2C60 and 4C60 fullerene molecules

The extended H?ckel method and the Green s function method were used to calculate the electronic structure and electrical transport of Au electrode-C₆₀, 2C₆₀ or 4C₆₀ fullerene-Au electrode systems. Furthermore, their electronic structure and electrical transport characteristics were compared and analyzed. The results show that (i) owing to the contact with the Au electrodes, the C₆₀, 2C₆₀ and 4C₆₀ molecules change in their electronic structures significantly, and their energy gaps between LUMO and HOMO are narrow; (ii) the bonding between C₆₀, 2C₆₀ or 4C₆₀ fullerene and Au electrodes is partially covalent and partially electrovalent; and (iii) the conductance of the three fullerenes conforms to the order of C₆₀>2C₆₀>4C₆₀.     

Trapping of solvent by a C60 fullerene film

Mass spectrometry was used over a wide temperature range to compare processes of solvent (toluene) release and desorption of C₆₀ fullerene molecules from a fullerite film formed from solution on an oxidized metal substrate. It is shown that toluene is strongly retained in the fullerite film and that it is almost impossible to remove the toluene from the film without damaging its structure. Quantitative characteristics of the toluene retention and trapping effect are determined. Pis’ma Zh. Tekh. Fiz. 24, 23–29 (December 12, 1998)     

Dispersed state of C60 fullerene in some polymers

The character of C₆₀ fullerene dispersion and its temperature dependence in various polymer matrices has been studied by UV-Vis spectroscopy and thermodesorption mass spectrometry. It is established that the degree of fullerene aggregation in these composites varies from molecular-dispersed state to largesize clusters. For the polymers studied, the initial dispersed state is most stable with respect to temperature in the case of poly-α-methylstyrene.

     

C60、Si@C60及Ge@C60富勒烯分子的电子传输特性

采用扩展的Hückel方法与格林函数方法,分析了双Au电极作用下,C60、Si@C60以及Ge@C60富勒烯分子的电子结构与导电性,并对三种富勒烯分子的电子结构与电子输运特性进行了对比.研究结果表明,C60、Si@C60或Ge@C60分子与Au电极"接触"后,其最高占据分子轨道与最低未占据分子轨道间的能隙减小,它们与Au电极之间的结合既有共价键的成分,又有离子键的成分;三种富勒烯分子的电子输运性能依次具有Ge@C60＞Si@C60＞C60的顺序.     

Organic fractal nano-dimensional structures based on fullerene C60

The ways for a synthesis of nanoporous and close-packed types of fullerene C₆₀ aggregates in two-component organic solvents (toluene?+?tetrahydrofuran) were established as well as their structural and dimensional features - were studied by high-resolution transmission electron microscopy and atomic-force microscopy methods. The physical features and regularities that characterize the processes of self-organization of fullerene molecules in the initial molecular solution were determined. The method for producing nanoscale fullerene C₆₀ fractal coatings (thickness up to ～1200?nm) on a flat dielectric glass surface was proposed.     

Semiconductor nanocrystals photosensitize C60 crystals

Semiconductor nanocrystals (SCNCs) made of CdSe, CdTe, and InP are used to photosensitize needlelike C(60) crystals. The photocurrent is increased by up to 3 orders of magnitude as compared with C(60) crystals without SCNCs. The photocurrent spectrum can be tuned precisely by the SCNC size and material, rendering the SCNC-functionalized C(60) crystals an excellent material for spectrally tuneable photodetectors. We explain the increased photocurrent as a result of photoexcited electrons transferring from the SCNCs to the C(60) crystals and causing photoconductivity, while the complementary holes remain trapped in the SCNCs.     

Synthesis of allyl-bearing dendrimers with a resorcinarene core and their supramolecular complexes with fullerene C60

Dendritic branches of poly(arylether) with peripherial allyl chains have been attached to a resorcinarene core. Dendrimers of first, second, and third generation were synthesized. Viability to form supramolecular complexes with fullerene C60 was studied with three dendrimers of first, second, and third generation. All the compounds were characterized by 1H, 13C NMR, FTIR, UV-vis spectroscopy, MALDI-TOF, FAB+ mass spectra, and elemental analysis. Strong pi-pi, CH-pi, and n-pi interactions between the dendrimers and the fullerene C60 were detected in the supramolecular complexes by UV-vis, FTIR, and 13C CP-MAS NMR.     

Influence of C60 fullerene on fretting wear of metals

The potential usefulness of C₆₀ as additives in lubricating oils and as coatings under fretting conditions is demonstrated by tribological techniques. Pis’ma Zh. Tekh. Fiz. 23, 1–6 (August 12, 1997)     

Thermodesorption states of fullerene C60 in the polyimide-fullerene system

The data of thermodesorption mass spectrometry indicate that fullerene C₆₀ molecules are desorbed from a polyimide (PI) surface at temperatures below the PI decomposition onset temperature, while the desorption of C₆₀ from the bulk begins in the temperature region of the polymer decomposition. It is suggested that strong chemical bonds between C₆₀ and PI macromolecules are formed in the bulk in the stage of the polyamic acid preparation and are broken upon destruction of the polymer macromolecules. The character of C₆₀ thermodesorption from the PI surface depends on thickness of the surface film of fullerene C₆₀.     

Modification of fullerene nanocolumn structure by accelerated C60 ions

Crystalline C60 and amorphous graphite-like films of nanocolumn arrays fabricated by glancing angle deposition of C60 fullerene at substrate temperatures of -425 K were studied by transmission electron microscopy (TEM) and atomic-force microscopy (AFM). Characteristic dimension of columns is 200-400 nm. We used co-deposition of C60 molecules and accelerated C60 ions to modify the structure and properties of nanocolumn arrays. Influence of incidence angle for C60 ions on formation of film morphology was revealed. Raman spectrum analysis showed that amorphous carbon nanocolumns consist of nanographite areas with average size of -1.5 nm. The films have high conductivity (close to graphite) and have no mechanical stresses. The carbon films were applied in all-solid-state rechargeable thin-film battery as an anode layer. The nanocolumn amorphous carbon film as anode electrode showed the discharge capacity of about 50 microAh cm(-2)microm(-1) and good cycling ability over 100 times in full cell system.     

Normal-incidence reflectance of crystalline K(6)C(60), Rb(6)C(60), and Cs(6)C(60)

The structure factors and normal-incidence reflectances of the alkali-metal-doped fulleride crystals M(6)C(60) (where M = K, Rb, or Cs) were calculated, and the peak reflectances are in the 2-20% range for incident wavelengths of 9-17 ?, which indicates that C(60) may be a promising transmissive (spacer) material for normal-incidence mirrors that have relatively high normal-incidence reflectance in the x-ray region.     

C60,C180,C60@C180富勒烯分子的压缩力学特性与电子结构

采用分子动力学方法模拟了C60,C180,C60@C180富勒烯分子的压缩过程,用PM3半经验量子力学方法计算了压缩C60,C180,C60@C180分子的电子结构,讨论了C60,C180,C60@C180分子压缩力学特性的差异,以及电子结构在压缩过程中的变化．结果表明,由于分子几何构形上的差异,C60分子的承载与吸收能量能力显著高于C180和C60@C180分子,而CC60@C180分子略高于C180分子;C60分子具有最高的化学稳定性,而C60@C180分子的稳定性最低;C60和C60@C180分子的压缩变形越大,越容易失去电子,稳定性越低;C180分子在加载点处发生压缩“塌陷”时,化学活性明显增加．     

Synthesis and Properties of Platinum Complexes of Fullerenes (C60 and C70)

Platinum complexes of C60 and C70 were synthesized and characterized by using spectroscopic analysis. The X-ray data of the C60-platinum complex containing no solvent of crystallization afforded the definite bond lengths and angles.