We report superconductivity in Cs3 C60 at 40K using ac susceptibility measurements under hydrostatic conditions up to 15 kbar. Cs3 C60 was prepared by reaction of C60 with Cs in liquid ammonia, followed by heating at 150°C. This route circumvents formation of the energetically more stable CSl C60 and Cs4 C60 phases. We have studied the synthesis and phase formation by measuring the symmetric Ag pentagonal pinch mode of C60 using Raman spectroscopy. Whereas Raman spectroscopy indicates homogeneous charge transfer of three electrons, x-ray diffraction indicates two phases other than the commonly observed fcc structure. This superconducting transition temperature is considerably higher than for known doped C60 compounds and intermetallic compounds.

The Na based mixed alkali doped C60 superconductors show anomalous behavior with respect to the “universal” superconducting transition temperature Tc vs lattice constant ao relation followed by most of the fcc A3C60 superconductors. We have measured dTc/dP for Na2CsC60 and (NH3)4Na2CsC60 using solid He as the pressure medium to ∼ 6 kbar finding dTc/dP equal to −0.88±(0.01) K/kbar and −1.0(±0.1) K/kbar for Na2CsC60 and Na2(NH3)4C60 respectively. Our value for Na2CsC60 differs markedly from that obtained by Mizuki et al of about −1.3 K/kbar. However, using N2 or Ar, we obtain values for dTc/dP in substantial agreement with Mizuki et al who used fluorinert to generate their pressure. This work emphasizes the need for compressibility measurements with the same pressure medium in the appropriate temperature range so that meaningful comparisons can be made between various pressure measurements and models which are based on lattice spacing.

The superconducting energy gap of Rb3C60 has been measured by infrared transmission through a thin film. Resistivity measurements on the same samples in situ indicate a transition to superconductivity at the expected temperature, ∼30K, with distinct gap features appearing in the transmission below this temperature. The results are interpreted in terms of the BCS theory.

High resolution electron energy loss spectroscopy has been used to investigate the vibrational and electronic excitations of single-phase, crystalline AxC60 films. Substantial changes in intramolecular mode frequencies and intensities with alkali concentration arise from charge transfer effects as well as free carrier screening. For x=4, splitting of the t1u band is observed, resulting in an insulating phase with an estimated gap of 0.3-0.4eV. Screening in the x=3 phase results in enhanced surface sensitivity and deviations from bulk stoichiometry at the surface of metallic films are observed.

In situ Raman scattering, UPS and HREELS measurements have been used to study the fcc to orthorhombic phase transition in RbC60 thin films. Large changes in the Raman spectra are interpreted in terms of increased interfullerene coupling in the orthorhombic phase. However, the data do not support the proposed polymer model for this phase. Photoemission measurements indicate only small differences in the electronic states between the two phases in contrast with photopolymerized C60 where additional states are observed. Low energy metallic-like excitations and screening of intramolecular vibrations are observed in HREELS.

A structure sequence of doped fcc, bct, bcc and Rb-saturated fcc phases was observed in C70Rbx with increasing Rb concentration using x-ray-diffraction measurements. The composition of the Rb-saturated phase was estimated to be C70Rb9.4±0.4 from a weight measurement. A model for the structure of C70Rb9 is proposed. Superconductivity in each phase was checked using ac magnetic-susceptibility measurements. All these phases were nonsuperconducting down to 1.3 K.

The infrared- and Raman-active vibrational modes of C60 were measured in the various structural states of Rb1C60. According to earlier studies, Rb1 C60 has an f cc structure at temperatures above ∼ 100°C, a linear chain polymer orthorhombic structure when slowly cooled, and an as yet undetermined structure when very rapidly cooled (“quenched”). We show that the spectra obtained in the polymer state are consistent with each C60 molecule having bonds to two diametrically opposite neighbors. In the quenched state, we find evidence for further symmetry breaking, implying a lower symmetry structure than the polymer state. The spectroscopic data of the quenched phase are shown to be consistent with Rb2(C60)2, a dimerization of C60.

The promising positive results in reducing superoxide free radicals (O2-.), generated by invitro xanthine and xanthine oxidase, have been demonstrated in the evaluation of potential uses of novel water-soluble [60] fullerenols as free radical scavengers. Observation reveals the inherent application of fullerenols in a wide range of medical and clinical areas as preventive alternatives for a long-term medical treatment.

Polyhydroxylated fullerene derivatives (fullerenols) were utilized as an efficient hypercross-linking agent for the synthesis of elastic poly(tetramethylene oxide)-based polyurethane networks with excellent thermal mechanical properties. Polyhydroxylated fullerenes were synthesized from the hydrolysis of polycyclosulfated fullerene derivatives in the presence of water at 85-90 °C or in aqueous NaOH solution at ambient temperature.

Small-angle neutron scattering (SANS) can structurally characterize fullerenes1 in solvents with strong SANS contrast (e.g. CS2). Deuterated solvents (e.g. toluene-d8) have a high scattering length density (SLD), which is close to that of C60 and C70 moieties. Hence, there is virtually no SANS contrast with the solvent and these particles are practically “invisible” in such media. On the other hand, the negative scattering length of hydrogen means that the SLD of H1-containing materials is much lower, so they have strong contrast with toluene-d8. Thus, SANS makes it possible to study the size and shapes of modified buckyballs such as the polymer-substituted fullerenes, or flagellenes2. These consist of C60 cores to which 1-4 polystyrene chains (with a molecular weight, MW ≃ 2000) are attached. The extrapolated cross section at zero angle of scatter [dΣ/dΩ(0)]s is a function of the number of pendant chains, so SANS can be used to assess the number of “arms” which are covalently attached to the fullerene “sphere”. Close agreement (± 4%) between the measured and calculated values of dΣ/dΩ(0) along with independent estimates of the radius of gyration (Rg) and second virial coefficient (A2) for a calibration linear polystyrene sample serves as a cross check on the validity of this methodology.

The dynamic behavior of the fullerenol-based polyurethane star-shaped polymer and its analog model stars, containing three or four polymer arms, was investigated in toluene solution by dynamic light scattering measurements. In these systems, the diffusion coefficients clearly showed no angular dependence. In the case of study in dilute solution, all three star polyurethanes were found to possess higher mobility than that of the corresponding linear polyurethane with a similar molecular weight. Furthermore, the conformation of anchoring polymer chains was characterized by the hydrodynamic shrinking factor and compared with the Gaussian model. Results suggested that the polymer arms in the fullerenebased star-polymer were uniformly distributed around the central C60 cage.

A one to ten adduct of C60 and 2-methylaziridine was prepared and copolymerized with Novolac, Epon and Bisphenol A to obtain three dimensional polymers containing C60 with low coefficients of friction and good wear properties, which bode well for their potential use as solid lubricants.

Fullerene C60 can be considered an interesting molecule for the preparation of new materials with attractive optical properties. In the present work we report the preparation of sol-gel derived, glass-like materials containing C60 and a C60 derivative prepared by 1,3-dipolar cycloadditions of azomethine ylides to C60. The optical characterisation of the films confirms the presence of C60 and its derivative, in the glass matrix.

Functionalization of C60 has been achieved by [2+2] photocycloaddition reactions of enones and [2+4] cycloaddition reactions of dienes, the course of these reactions can be followed using electrospray mass spectrometry using a special tagging reagent. Using tagged C60 it was shown that cis and trans cycloadducts are formed from ketones such as 3-methylcyclohexenone. We have also employed the new technique of 3He NMR spectrometry. 3He is an NMR-active nucleus. Fullerenes containing an endohedral 3He atom can be examined by NMR to obtain structural information and potentially determine isomer distributions. Examples, of helium spectra of fullerene hydrides are presented.

Semiempirical and ab initio Hartree Fock computational results indicate that the highly reactive dienophile tetramethyldisilene, Me2Si=SiMe2, is an excellent candidate for a novel functionalization of the equator of C70 via a [2+4] cycloaddition to the 21, 22, 23, 42 carbons. Thermal or photochemical generation of tetramethyldisilene in the presence of C70 results in similar complex mixtures in which the major product appears to be that of [2+2] cycloaddition to the 7,8 carbons of C70. A minor product clearly results from [2+2] cycloaddition to the 1,9 carbons. Both of these products are hydrolytically unstable and are converted nonspecifically to mixtures of 1,9- and 7,8-C70H2 which are also present in HPLC traces of the reaction mixtures.

The construction of nanoscale devices is a potentially important area of technology. Efforts in this area of chemistry have largely concentrated on the preparation of rigid organic molecules for use as spacers. These compounds are used to separate electronically active units, usually metal complexes, by defined distances.

We have been investigating the use of fullerenes as connectors in the construction of these extended assemblies. In this paper we will present our results on the preparation of these compounds, including discussions of the regiochemistry of the second addition of a nitrile oxide to a fullerene isoxazoline.

We have employed scanning tunneling microscopy at room and low temperature, i.e. 300, 50, and 5 K, to study the epitaxy and growth of fullerene films on the noble-metal surfaces Ag(110) and Au(110). Initial island growth occurs on terrace sites away from substrate step edges. Particularly at low temperatures where the rotational and vibrational movements of the fullerene molecules are frozen in, different intra-molecular topographic patterns become visible in ordered films, which are characteristic of particular adsorption sites. Complementary tunneling spectroscopy and direct and inverse photoemission measurements reveal distinct differences between the first adsorbed monolayer and additional fullerene layers indicating differences in bonding and charge transfer. Our results are compared to theoretical calculations.

The effect that the presence or absence of interfacial C60 layers has on the nucleation and subsequent growth of overlying thin metal films has been studied using in situ resistivity measurements. Comparisons are made for Al and Cu films grown on quartz and yttria stabilized zirconia (YSZ) substrates. Our results indicate that electron donation across M/C60 (M=Al, Cu) interfaces reduces the percolation threshold for conductivity while simultaneously giving rise to an increased resistance in the metal due to electron depletion. Additional physical processes that are taken into account include the effect of different interfacial energies at the M/C60 and M/substrate boundaries and the effect of substrate tunneling between percolating metallic islands during the initial stages of film growth.

High quality C60 films are grown on surfaces of (111) oriented noble metal substrates (i.e., Au, Ag, and Cu) by using a molecular beam deposition method. The structures of these films are compared with each other on substrates that are prepared to have similar in-plane mosaic widths (σ1.25*) as determined by their x-ray diffraction scans. The in-plane structures of these films are studied for substrate temperatures ranging from σ110 to 290°C. Although most materials grow in high symmetry small-lattice-mismatch in-plane orientations, C60 films (depending on their growth temperatures) grow in orientations that are poorly lattice matched with their Au(111) and Ag(111) substrates. In these orientations, C60 structures can be lattice matched only over large unit cells, forming “long-period ” structures. These “long-period ” structures coexist with “commensurate” structures that are almost perfectly lattice matched on twheitshe osur bpsrterdaotems.i naOten Au(111) substrates, a structural transition is observed between two distinct long-period structures (at Tc, σ150 °C). Although Au and Ag have similar lattice spacings, this transition is absent on Ag(111) substrates. The question of orientational epitaxy for C60 layers is examined in the context of several well-known systems in condensed matter physics.

On mica(001) thin C60-films are deposited by thermal evaporation at substrate temperatures from room temperature up to 225°C. The dependence of the structure and the epitaxial alignment of the thin C60-films on mica(001) on the substrate temperature and the film thickness up to 1.3 μm at a well-defined deposition rate (0.008 nm/s) is investigated by atomic force microscopy and X-ray diffraction. The shape and the size of the C60-islands, which have an influence on the film quality at larger film thicknesses, are sensitively dependent on the substrate temperature. At a film thickness of 200 nm the increase of the substrate temperature up to 225°C leads to smooth, completely coalesced epitaxial C60-thin films characterized by a roughness smaller than 1.5 nm, a mosaic spread Δω of 0.1° and an azimuthal alignment ΔΦ of 0.45°.