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Pulsed laser ablation (PLA) has been scaled up to yield several grams/day of single-walled nanotubes. Annealed, purified material is highly crystalline, essentially free of amorphous carbon, fullerenes and catalyst residues, and about 3 times denser than the highly porous, as-grown product. In principle the interactions between tubes in a rope, and/or between rope crystallites, may be “tuned” by 3 different approaches—chemical doping, hydrostatic pressure, or purification/annealing, all of which have a dramatic effect on the temperature dependence of resistivity. In particular, we suggest that the crossover from positive to negative dR/dT at low temperature is a 3D effect and not an intrinsic property of isolated neutral SWNT.

Bundles of carbon single wall nanotubes (SWNTs) are produced by sublimating selected metal mixtures and carbon in an inert atmosphere during an electric arc [1]. Various experimental parameters such as the nature and relative proportions of metallic catalysts [1] or the kind and pressure of gas can influence the quantity and geometry of bundles produced by the arc process. In this paper, we particularly focus on the role of the nature and pressure of gas used. Systematic studies have been made and we present the results obtained by Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), X-Ray Diffraction (XRD) and High Resolution Raman Spectroscopy (HRRS).

Single-walled carbon nanotubes (SWNTs) offer the prospect of both new fundamental science and useful (nano)technological applications1. High yields (70–90%) of SWNTs close-packed in bundles can be produced by laser ablation of carbon targets2. The electric-arc technique used to generate fullerenes and multi-walled nanotubes is cheaper and easier to implement, but previously has led to only low yields of SWNTs3,4. Here we show that this technique can generate large quantities of SWNTs with similar characteristics to those obtained by laser ablation. This suggests that the (still unknown) growth mechanism for SWNTs must be independent of the details of the technique used to make them. The ready availability of large amounts of SWNTs, meanwhile, should make them much more accessible for further study.

Semi-empirical and ab initio calculations [1], as well as inelastic neutron spec-troscopy [2], demonstrate that Li can bind to protonated “edge carbons” to create a moiety analogous to the organolithium monomer C2H2Li2. This provides a possible additional channel for Li uptake in high capacity Li-ion battery anodes based on low-T pyrolyzed soft carbons. Here we show that similar reactivity is exhibited by polyaro-matic hydrocarbons with the protons removed (taken as surrogates for the structural units in hard carbons). In the deprotonated PAH'es the Li serves to saturate dangling bonds, maintaining sp2 hybridization, whereas Li added to PAH'es creates sp3 carbons at the edges. In both cases this extra reactivity occurs in parallel with the usual intercalation. These findings have implications for further development in Li-ion rechargeable battery technology.

Nonchiral single wall carbon nanotubes with an "armchair" wrapping are theoretically predicted to be conducting, and high purity samples consisting predominantly of these tubes exhibit metallic behavior with an intrinsic resistivity which increases approximately linearly with temperature over a wide temperature range. Here we study the coupling of the conduction electrons to long wavelength torsional shape fluctuations, or twistons. A one dimensional theory of the scattering of electrons by twistons is presented which predicts an intrinsic resistivity proportional to the absolute temperature. Experimental measurements of the temperature dependence of the resistivity are reported and compared with the predictions of the twiston theory., Comment: 4 pages REVTeX, 2 postscript figures

The poor performance of hydrogen storage materials continues to hinder development of fuel cell-powered automobiles. Nanoscale carbons, in particular (activated carbon, exfoliated graphite, fullerenes, nanotubes, nanofibers, and nanohorns), have not fulfilled their initial promise. Here we show that carbon materials can be rationally designed for H2 storage. Carbide-derived carbons (CDC), a largely unknown class of porous carbons, are produced by high-temperature chlorination of carbides. Metals and metalloids are removed as chlorides, leaving behind a collapsed noncrystalline carbon with up to 80% open pore volume. The detailed nature of the porosity-average size and size distribution, shape, and total specific surface area (SSA)-can be tuned with high sensitivity by selection of precursor carbide (composition, lattice type) and chlorination temperature. The optimum temperature is bounded from below by thermodynamics and kinetics of chlorination reactions and from above by graphitization, which decreases SSA and introduces H2-sorbing surfaces with binding energies too low to be useful. Intuitively, pores of different size and shape should not contribute equally to hydrogen storage. By correlating pore properties with 77 K H2 isotherms from a wide variety of CDCs, we experimentally confirm that gravimetric hydrogen storage capacity normalized to total pore volume is optimized in materials with primarily micropores ( approximately 1 nm) rather than mesopores. Thus, in agreement with theoretical predictions, a narrow size distribution of small pores is desirable for storing hydrogen, while large pores merely degrade the volumetric storage capacity.

Liquid anhydrous sulfuric acid forms molecular “shells” wrapped around single-walled carbon nanotubes (SWNTs). Temperature-dependent X-ray scattering from aligned acid-swollen fibers shows that crystallization of the bulklike acid surrounding the structured shells is templated by the aligned SWNTs, while the structured shells remain partly ordered, at least for temperatures from 100 to 500 K. The (2 0 0) or (2 0 2) planes of the templated H2SO4 crystallites are parallel to the nanotube axes. This provides solid evidence for the direct protonation of SWNT since the molecules are terminated by hydrogen bonds.

Objective: To determine whether oxygenation and lung mechanics are preserved during perfluorocarbon associated gas exchange of 24 hrs duration and after evaporation of perfluorocarbon. Design: Prospective, experimental animal trials. Setting: Animal laboratory in a university setting. Subjects: Ten normal, neonatal piglets weighing 2.5 to 4.5 kg. Interventions: Ten piglets were anesthetized with fentanyl (25 μg/kg/hr), paralyzed with metocurine iodide (0.3 mg/kg) and placed on volume regulated continuous positive pressure breathing instituted at an FIO 2 setting of 1.0, tidal volume of 15 mg/kg, respiratory rate of 25 breaths/min and positive end-expiratory pressure of 4 cm H 2 O. Perfluorocarbon associated gas exchange was initiated by intratracheal instillation of perflouorooctylbromide (30 mL/kg) followed by gas ventilation at the same settings. Evaporative losses were replaced by intratracheal instillation of 2.5 mL/kg/hr of perfluorocarbon. In one group of five piglets, evaporative losses were replaced for 24 hrs until the end of the study. In the other group of five piglets, replacement of perfluorocarbon was discontinued after 2 hrs, although gas ventilation was continued for 24 hrs. Blood gases and lung mechanics were measured in both groups. Histologic evaluation of lungs from both groups of animals was performed. Measurements and Main Results: Airway pressures and blood gases were stable throughout the 24-hr study period in both groups. Airway pressures in the evaporative group increased as evaporation of perfluorocarbon neared completion. There was no hemodynamic deterioration during the 24-hr study period. Histology showed good preservation of lung architecture in both groups. Conclusions: Perfluorocarbon associated gas exchange was safe and effective in normal piglets for a period of 24 hrs. Evaporation of perfluorocarbon and resumption of continuous positive pressure breathing was well tolerated

We report results of high-resolution x-ray diffraction, dc magnetometry and Raman scattering on the quaternary alkali and ternary mixed alkali-alkaline earth fullerene compounds Na2RbxCs1−x C60 (0 < x < 1) and Rb3−δ BaδC60 (δ ∼ 0.4 and 2.0). These have the same cubic space lattices as K3C60 and Rb3C60 however the former exhibit long-range orientational correlations with Pa3 symmetry and the latter have N > 3 delocalized electrons per molecule. We show that the dependence of Tc on lattice constant is much steeper for the ordered as compared to the merohedrally disordered phases with N = 3, and that within the constraint of cubic symmetry Tc decreases significantly with increasing N > 3, in disagreement with some theoretical predictions.

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.

Although fullerenes and their compounds are very new and exhibit new phenomena, pressure has already been an important factor in the characterization and study of these materials. In order to illustrate this, we will review collaborative studies on: i) the effect of pressure on alkali and alkaline earth doped C60 superconductors, ii) the effect of pressure and pressure medium on the ordering temperature of C60, and iii) the role of pressure in the study of the feasibility of using C60 as ‘‘lattice sieves’’ for separation of gases.

In a previous paper1 we reported on the first synthesis of lithium intercalation into C60. The intercalation was performed electrochemically by using all-solid-state coin-type cells with P(EO)8 LiClO4 polymer electrolyte operated at 80°C. Five reduction steps have been clearly evidenced at 2.4, 1.9, 1.5, 1.0 and 0.8 V vs. Li/Li+. The domain limits for these successive steps appeared at 0.5, 2, 3, 4 and 12 lithiums per C60 respectively and the intercalation was observed to be reversible at least for the three first steps, ie. provided the potential to be confined within the 1.3–3.0V range vs. lithium. From a detailed analysis of the dynamics of the intercalation, as observed with step potential electrochemical spectroscopy, we have shown also that the two first intercalation/reduction steps correspond to first order transitions from pristine C60 to Li0.5C60 at 2.36V and then to Li2C60 at 2.0V, whereas the third one, from Li2C60 to Li3C60 corresponds to a solid solution single phase domain2, 3. Moreover on first reduction the Li0.5C60 phase appeared to form only at about 50 mV below the 2.42V open circuit value of the C60/Li0.5C60 two phase equilibrium, beginning with an increase of the insertion current at constant potential once initiated. This was attributed to the specificity of the surface of solid C60 which offers very few nucleation centers for chemisorption and intercalation, due to the absence of dangling bonds: once initiated the intercalation kinetics increase with the growing of the new Li0.5C60 phase.

This review addresses the field of nanoscience as viewed through the lens of the scientific career of Peter Eklund, thus with a special focus on nanocarbons and nanowires. Peter brought to his research an intense focus, imagination, tenacity, breadth and ingenuity rarely seen in modern science. His goal was to capture the essential physics of natural phenomena. This attitude also guides our writing: we focus on basic principles, without sacrificing accuracy, while hoping to convey an enthusiasm for the science commensurate with Peter's. The term 'colloquial review' is intended to capture this style of presentation. The diverse phenomena of condensed matter physics involve electrons, phonons and the structures within which excitations reside. The 'nano' regime presents particularly interesting and challenging science. Finite size effects play a key role, exemplified by the discrete electronic and phonon spectra of C(60) and other fullerenes. The beauty of such molecules (as well as nanotubes and graphene) is reflected by the theoretical principles that govern their behavior. As to the challenge, 'nano' requires special care in materials preparation and treatment, since the surface-to-volume ratio is so high; they also often present difficulties of acquiring an experimental signal, since the samples can be quite small. All of the atoms participate in the various phenomena, without any genuinely 'bulk' properties. Peter was a master of overcoming such challenges. The primary activity of Eklund's research was to measure and understand the vibrations of atoms in carbon materials. Raman spectroscopy was very dear to Peter. He published several papers on the theory of phonons (Eklund et al 1995a Carbon 33 959-72, Eklund et al 1995b Thin Solid Films 257 211-32, Eklund et al 1992 J. Phys. Chem. Solids 53 1391-413, Dresselhaus and Eklund 2000 Adv. Phys. 49 705-814) and many more papers on measuring phonons (Pimenta et al 1998b Phys. Rev. B 58 16016-9, Rao et al 1997a Nature 338 257-9, Rao et al 1997b Phys. Rev. B 55 4766-73, Rao et al 1997c Science 275 187-91, Rao et al 1998 Thin Solid Films 331 141-7). His careful sample treatment and detailed Raman analysis contributed greatly to the elucidation of photochemical polymerization of solid C(60) (Rao et al 1993b Science 259 955-7). He developed Raman spectroscopy as a standard tool for gauging the diameter of a single-walled carbon nanotube (Bandow et al 1998 Phys. Rev. Lett. 80 3779-82), distinguishing metallic versus semiconducting single-walled carbon nanotubes, (Pimenta et al 1998a J. Mater. Res. 13 2396-404) and measuring the number of graphene layers in a peeled flake of graphite (Gupta et al 2006 Nano Lett. 6 2667-73). For these and other ground breaking contributions to carbon science he received the Graffin Lecture award from the American Carbon Society in 2005, and the Japan Carbon Prize in 2008. As a material, graphite has come full circle. The 1970s renaissance in the science of graphite intercalation compounds paved the way for a later explosion in nanocarbon research by illuminating many beautiful fundamental phenomena, subsequently rediscovered in other forms of nanocarbon. In 1985, Smalley, Kroto, Curl, Heath and O'Brien discovered carbon cage molecules called fullerenes in the soot ablated from a rotating graphite target (Kroto et al 1985 Nature 318 162-3). At that time, Peter's research was focused mainly on the oxide-based high-temperature superconductors. He switched to fullerene research soon after the discovery that an electric arc can prepare fullerenes in bulk quantities (Haufler et al 1990 J. Phys. Chem. 94 8634-6). Later fullerene research spawned nanotubes, and nanotubes spawned a newly exploding research effort on single-layer graphene. Graphene has hence evolved from an oversimplified model of graphite (Wallace 1947 Phys. Rev. 71 622-34) to a new member of the nanocarbon family exhibiting extraordinary electronic properties. Eklund's career spans this 35-year odyssey.

The temperature dependent structural evolutions of RbxC60 (x = 3, 5, 6) and K4C60 were studied using both in-house andsynchrotron x-ray powder diffraction and thermal analysis techniques over a temperature range of 10K - 673K. The superconducting face centered-cubic (fcc) Rb3C60 and the body centered-tetragonal (bct) M4C60(M = K, Rb) phases are found to be line compounds in this temperature range, while the body centered-cubic (bcc) phase forms a solid solution in which the solubility of vacant M sites increases with temperature. The orientation of the C60 molecules in the K4C60 phase was analyzed. A crystalline fcc Rb1C60 phase is stable only above room temperature.

We report measurements of thermal conductivity κ on individual gallium nitride nanowires (GaN NWs) with diameters ranging from 97to181nm grown by thermal chemical vapor deposition. We observed unexpectedly small κ values, in the range of 13–19W∕mK at 300K, with very weak diameter dependence. We also observe unusual power law κ∼Tn behavior with n=1.8 at low temperature. Electron-energy-loss-spectroscopy measurements indicate Si and O concentrations in the ranges of 0.1–1 and 0.01–0.1at.%, respectively. Based on extensive numerical calculations, we conclude that both the unexpectedly low κ and the T1.8 dependence are caused by unusually large mass-difference scattering, primarily from Si impurities. Our analysis also suggests that mass-difference scattering rates are significantly enhanced by the reduced phonon group velocity in nanoscale systems. Planar defects running the length of the NW, previously characterized in detail, may also play a role in limiting the phonon mean free path.

High performance ambipolar silicon nanowire (SiNW) transistors were fabricated. SiNWs with uniform oxide sheath thicknesses of 6–7nm were synthesized via a gas-flow-controlled thermal evaporation method. Field effect transistors (FETs) were fabricated using as-grown SiNWs. A two step annealing process was used to control contacts between SiNW and metal source and drain in order to enhance device performance. Initially p-channel devices exhibited ambipolar behavior after contact annealing at 400°C. Significant increases in on/off ratio and channel mobility were also achieved by annealing.

High-quality silicon nanowires (SiNWs) were synthesized via a thermal evaporation method without the use of catalysts. Scanning electron microscopy and transmission electron microscopy showed that SiNWs were long and straight crystalline silicon with an oxide sheath. Field effect transistors were fabricated to investigate the electrical transport properties. Devices on as-grown material were p-channel with channel mobilities 1–10cm2V−1s−1. Postgrowth vapor doping with bismuth converted these to n-channel behavior.

Nanopatterned Pt by Ga+ focused ion beam (FIB) decomposition of an organometallic precursor forms low resistance ohmic contacts on 40–70nm diameter GaN nanowires (NWs) grown by thermal reaction of Ga2O3 and NH3. With no intentional doping, the wires are presumed to be n type. Thus, the linear I‐V behavior is surprising since evaporated Pt usually forms Schottky barriers on n GaN. Ohmic behavior was not obtained for 130–140 diameter wires, even with thicker Pt contacts. A second application of FIB Pt nanopatterning was demonstrated by position-selective growth of GaN NWs on Pt catalyst dots. NW locations and density are defined by the position, size, and thickness of the Pt deposit. Combining these techniques provides a versatile platform for nanostructure research and development.

Nanoporous carbons obtained by selective leaching of Ti and Al from Ti2AlC, as well as B from B4C, were investigated as electrode materials in electric double-layer capacitors. Cyclic voltammetry tests were conducted in 1 M H2SO4 from 0-250 mV on carbons synthesized at 600, 800, 1000, and 1200°C. Results show that the structure and pore sizes can be tailored and that the optimal synthesis temperature is 1000°C. Specific capacitances for Ti2AlC CDCs and B4C CDCs were 175 and 147 F/g, respectively, compared to multiwall carbon nanotubes and two types of activated carbon, measured herein to be 15, 52, and 125 F/g, respectively. © 2005 The Electrochemical Society. @DOI: 10.1149/1.1921134# All rights reserved.

This work relates to a rigorous study of the surface chemistry (Fourier transform infrared, X-ray photoelectron spectroscopy), crystal structure (X-ray diffraction), galvanostatic, cyclic voltammetric, and impedance behavior of lithiated carbon electrodes in commonly used liquid electrolyte solutions. Two different types of disordered carbons and graphite as a reference system, were explored in a single study. All three types of carbons develop a similar surface chemistry in alkyl carbonate solutions, which are dominated by reduction of solvent molecules and anions from the electrolyte. The differences in the crystal structure of these carbons lead to pronounced differences in the mechanisms of Li insertion into them Whereas Li-ion intercalation into graphite is a staged process, Li-ion insertion into the disordered carbons occurs in the form of adsorption on both sides of the elementary graphene flakes and on their edges. The electroanalytical behavior of the disordered carbons was found to correlate well with their unique structure described in terms of the butterfly model. Both types of the disordered carbons reveal exceptionally good cyclability in coin-type cells (vs Li counter electrodes), with only moderate capacity fading. Highly resolved plots of the chemical diffusion coefficient of Li-ions. D vs. potential E, for the disordered carbon electrodes were obtained. Surprisingly, a maximum in D appears on these plots at intermediate levels of Li-ion insertion corresponding to ca. 0.4-0.5 V (vs. Li/Li + ). We propose that these maxima may originate from a combination of two effects, (i) repulsive interactions between the inserted species, and (ii) pronounced heterogeneity of Li insertion sites in terms of carbon-Li interactions and Li-ion mobility.

Electrochemistry has proven to be very useful for the study of guest-host systems, particularly, carbon intercalation compounds. Not only does electrochemistry provide essential information about the thermodynamics and kinetics of these systems, but it also offers accurate control of guest stoichiometry which is difficult to achieve by other doping methods. Therefore, electrochemical doping has been used extensively to study the properties of carbon guest-host systems. In situ X-ray diffraction and electrochemical doping were used to study the phase diagram of Li xC6 graphite, 1 phase transitions in Li-doped polyacetylene 2 and the structure of Li-doped solid C 60. 3 In situ resistivity measurements were used to study the electronic transport properties of K- and Na-doped polyacetylene. 4,5 In this work, electrochemistry was used to study a new carbon guest-host system: Li/carbon nanotubes. Two types of carbon nanotubes can be distinguished according to their structural properties: multiwall (MWNT) and single wall (SWNT). 6 MWNT consist of graphitic sheets rolled into closed concentric cylinders, with a structure similar to that of Russian dolls. The concentric tubes are separated by Van der Waals gaps of ,3.4 A, a typical interlayer spacing in turbostratically disordered graphite. External diameters can be as large as 50 nm, and lengths are of micrometer scale. SWNT can be envisioned as a single graphene sheet rolled into a cylinder, with diameters in the range 1-2 nm and lengths of several micrometer. SWNT of nearly uniform diameters self-organize into long crystalline “ropes” in which parallel nanotubes are bound by Van der Waals forces. 7 The diameter of a rope is typically 10-50 nm corresponding to 30-600 tubes per rope. Ropes containing as few as 2-3 tubes or as many as several thousand are occasionally found. Figure 1 presents a high resolution transmission electron microscope (HRTEM) image of purified and annealed SWNT, in which several entangled ropes with different diameters can be observed. The parallel fringes within each rope are due to the constructive scattering from the parallel planes of SWNT. The fact that the fringe spacings differ among ropes does not arise from a wide distribution in nanotube diameters, but rather from the different orientation of each rope zone axis with respect to the electron beam. Figure 2 shows an X-ray profile from purified and annealed SWNT. The well

Fluorination of the fullerene, C60, has been previously reported. In one case the reaction was reported to proceed rapidly, initially, but final products obtained were not fully fluorinated, although molecules up to stoichiometry C60F52 were observed [H. Selig et al., J. Am. Chem. Soc., 113 (1991) 5475]. Another report claims that the fluorination proceeds extremely slowly, but that the fully fluorinated C60F60 was obtained [J.H. Holloway et al., J. Chem. {Soc., Chem. Comm.}, (1991) 966]. We discuss here possible explanations for the reported discrepancies. The fluorinated product of average stoichiometry C60F42 crystallizes in a face-centered cubic lattice with cell constant a0=17.1 A, implying 12.1 A separation between the fluorinated molecules. This is consistent with expansion of the C60 sphere to a fluorinated one. Although mostly C60Fx with even x are obtained, there is some evidence that very low concentrations with odd x are also produced. These latter compounds give rise to an ESR signal which is split into a doublet by adjacent fluorines. The fluorinated molecules are soluble in many organic solvents giving yellow solutions with aromatic solvents and colorless solutions with saturated solvents, such as cyclohexane, with a strong absorption at 212 nm. The solutions can be spin-cast giving very thin layers of the fullerenes and fluorinated fullerenes. The lubrication properties of such films have been measured indirectly and compared with Teflon. Fluorination experiments with C70 will be discussed.

We have measured the reflectivity spectra of stages 1 and 2 graphite intercalated with KHg amalgam (KHgC4 and KHgC8) from 0.5–6eV, and compared them to the corresponding stages 1 and 2 binary compounds, KC8 and KC24. Plasma edges for the ternaries appear at about the same energies as in the binaries, but differences are observed in the reflectivity values at the minima. Kramers-Kroenig analysis yields thresholds for the onset of interband transitions at 1.3eV and 1.2eV for KHgC4 and KHgC8, compared to 2.7eV and 1.7eV for KC8 and KC24. The thresholds are explained in terms of interband transitions in the mercurographitides involving the Hg levels. A model for these transitions is presented based on the Mott metal-semiconductor transition in mercury. This model is shown to be consistent with the hypothesis that the mercury layers are negatively charged.

We present a selective review of recent progress in understanding the electronic properties of graphite intercalation compounds. Emphasis will be placed on the following points: (1) screening of ionized intercalant layers by free carriers, leading to 2D metallic behavior for dilute compounds; (2) comparison of N ( E F ) values among several compounds, showing that the best conductors have the lowest N ( E F ); (3) evidence for covalent interactions between C and I layers which limit the conductivity enhancement. The high basal plane conductivity of acceptor-type intercalation compounds of graphite is currently thought to be related to the acid strength of the intercalant. The stronger the acid, the greater the fractional electron transfer from graphite to molecule, hence the greater the density of delocalized holes on the graphite layers. It now appears that high basal conductivity also correlates with large anisotropy. Furthermore, strong acids might ultimately be detrimental to high σ if they attack the C layers directly, puckering them and hence reducing the mobility. Evidence for these effects will be reviewed.

In the stage-2 graphite intercalation compound LiC 12 the spin-lattice relaxation rate T 1 −1 of β-active 8 Li (T 1 2 = 0.8s) nuclei was measured as a function of temperature T and external magnetic field B. Two regions of different T dependences were found. Below 100K the coupling to electrons dominates T 1 −1 . Between 100K and 300K an additional contribution to T 1 −1 showed up which was found to be thermally activated. Long range Li-diffusion as relaxation mechanism could be ruled out due to the weak B dependence of the relaxation rate.

Previous observations suggested that synergy between antimicrobials and phagocytes may occur during Nocardia asteroides infection. We incubated N. asteroides with seven antimicrobials, and then exposed the nocardiae to phagocytes. Neutrophils and monocytes killed about half the nocardiae whether or not the nocardiae had been preincubated with antimicrobials. We also determined whether exposure to neutrophils led to increased susceptibility of nocardiae to antimicrobials, and it did not. We found no evidence for synergy between antimicrobials and phagocytes in host defence against this bacterium.

We have measured the X-ray photoelectron (XPS) spectra of the stage 1 and 2 mercurographitides KHgC 4 and KHgC 8 , and compared them with the corresponding binary intercalation compounds KC 8 and KC 24 . Relative to the Fermi energy, the K peaks appear at lower binding energies in the ternaries than in the binaries, while the C(1s) levels are at roughly the same energies. Referring the peaks to the original graphite Fermi level we find that the K(2p) peaks are shited to markedly lower binding energy in the ternaries than in the binaries; this shift is most pronounced for the second stage compounds. We interpret this as clear evidence that the potassium atoms are not fully ionized in the ternaries as they are in the binaries. We discuss the relationship between the stage dependence of the K(2p) shift and the observed superconductivity of these compounds. The Hg core levels occur at lower binding energy in both KHgC 4 and KHgC 8 than in Hg metal, consistent with the suggestion by the Nancy group that Hg carries a net negative charge in the mercurographitides.

We present Angle Resolved Photoemission measurements for Cs and K compounds peeled at 150K under ultrahigh vacuum. The structure and the composition of (at least) the uppermost intercalated layer in alkali metals GIC, differs strongly from the bulk structure and composition. The observed bands are in excellent agreement with σ and π bands expected from recent theoretical calculations, except for (i) the zone folding and (ii) the shape of the bands within 2 eV from the Fermi level. Near the Fermi level, a high intensity band is observed with a low dispersion (≈0:5 eV) throughout the whole Brillouin zone. We show that a first intercalated layer with a high intercalant concentration, exhibiting an incommensurate structure, accounts very well for all observed features. This structure gives rise to the band observed near the Fermi level, which is most probably a charge density wave.

Staging structure and kinetics in cesium-intercalated graphite were studied in situ using x-ray diffraction. The stage disorder was characterized via detailed Hendricks-Teller model analyses of (00L) profiles corresponding to various stage configurations. Broad distributions of stages were obtained under equilibrium conditions. Both stage purity and phase separation decreased with decreasing concentration; stages 5 and higher were highly miscible, while stages 3 and 2 completely phase separated. The miscibility also varied non-monotonically during a stage-n--to--(n-1) transition, suggesting that the kinetics are island-growth dominated towards the middle of the transition. We propose that the miscibility gap observed in a previous study of potassium graphite is caused by the enhanced development of stage-(n-1) cells with increasing chemical potential (or time), triggered by island growth; as these equilibrate, a discontinuously large stage-(n-1) volume results. Finally, an estimate for the exponent in the power-law repulsion between intercalate layers in alkali-graphite systems is made.

Elastic and inelastic neutron scattering are reported for C 8 Rb in the temperature range 4 – 800 K. Several phase transitions above room temperature are reported for the first time; these consist of changes in metal layer stacking and ultimately, at 747 K, the onset of 2D liquid behavior. Phonon dispersion of LA and LO modes propagating along c imply a 20% increase in the interlayer force constant relative to pure graphite. The zone boundary TA mode softens dramatically with increasing temperature, which may be related to the phase transitions.

Room temperature measurements of the 0.07–2.0 eV optical reflectance of carefully prepared stage 1–4 AsF5-graphite intercalation compounds have been performed. Stages 1–3 show simple metallic behavior with a well-defined plasma edge. Curve fits to the data give good agreement between dc and optical conductivities for stage 1 and 2. Comparison between stage 2 data for AsF5 and HNO3 compounds suggests that the higher conductivity of the former arises from a longer carrier relaxation time rather than from a greater carrier density.

Solid‐state physicists are turning more and more to complex synthetic materials in their search for novel phenomena and potentially useful properties. Many of these materials are highly anisotropic, so that interatomic interactions can for all practical purposes be neglected along one or two crystal axes. One of the oldest classes of prototype systems for exploring phenomena predicted to occur in two‐dimensional systems are graphite intercalation compounds. These consist of stacks of one or more layers of hexagonally arrayed carbon atoms, alternating with monolayers of guest atoms or molecules. Striking changes in the properties of both host and guest result from intercalation. In addition to their quasi‐two‐dimensional behavior, fundamental interest centers on their variable anisotropy, which results from the fact that the strength of the interlayer interactions depends on the nature of the intercalated species.

A brief review is presented of diffraction measurements versus temperature or pressure at fixed total concentration on Li- and K-GICs respectively. The observed staging transitions exhibit a wide variety of behavior, not all of which can be understood in terms of existing models. Very weak “superlattice” reflections in dilute Li compounds at high T are attributed to a small but finite effect of the host elastic energy, revealed by an increasingly small difference between the thicknesses of filled and empty galleries as the in-plane density approaches zero.