Reduction of Ecuadorian asphaltenes by lithium in liquid ammonia (Birch conditions) yields asphaltene salts that can be protonated by tert-butyl alcohol to yield deflocculated hydroasphaltene. Studies were carried out using asphaltenes from both low- and high-viscosity oils. The dimensions of the hydroasphaltenes were determined by atomic force microscopy. Relative to the starting asphaltene, the nominal asphaltene aggregate height of the low-viscosity asphaltene 1 was reduced from 1.3 to 0.7 nm, indicating that the asphaltene was fully exfoliated. The height of the high-viscosity asphaltene 2 was reduced from 4 to 2 nm. 13C nuclear magnetic resonance of the Birch-reduced asphaltenes shows a reduction in aromaticity from 49 to 46%, indicating that a low level of hydrogen was added to the aromatic core during the Birch reduction.

Diatoms in ice cores have been used to infer regional and global climatic events. These archives offer high-resolution records of past climate events, often providing annual resolution of environmental variability during the Late Holocene. Recently, the first low-latitude tropical diatoms were described from the Quelccaya Summit Dome. Here, we document diatoms observed in ice cores from Quelccaya, spanning AD 1300 to 1815, along with those from two additional glaciers (Coropuna, and Sajama glaciers) in the tropical Andes, spanning AD 1764 to 1814. Diatom assemblages recovered from these three sites were rare, but differ in abundance and species composition through time. Assemblages are characterized by cosmopolitan and aerophilic species, mostly pennate diatoms. There were 44 taxa in all, with Pinnularia cf. borealis Ehrenberg being the most common species encountered in the samples. Eleven taxa were found at all three sites. Both Coropuna and Sajama had taxa that were unique to these locations, whereas Quelccaya had no unique taxa. Due to the rarity of diatoms and the cosmopolitan nature of the dominant species, it is not possible to determine their origin, limiting their utility in paleoclimate reconstructions.

CONSPECTUS: As a result of the unique physical and electrical properties, graphene continues to attract the interest of a large segment of the scientific community. Since graphene does not occur naturally, the ability to exfoliate and isolate individual layers of graphene from graphite is an important and challenging process. The interlayer cohesive energy of graphite that results from van der Waals attractions has been determined experimentally to be 61 meV per carbon atom (61 meV/C atom). This requires the development of a method to overcome the strong attractive forces associated with graphite. The exfoliation process that we, and others, have investigated involves electron transfer into bulk graphite from intercalated lithium to yield lithium graphenide. The resulting graphenide can be reacted with various reagents to yield functionalized graphene. As a part of our interest in the functionalization of graphene, we have explored the Birch reduction as a route to hydrographenes. The addition of hydrogen transforms graphene into an insulator, leading to the prediction that important applications will emerge. This Account focuses mainly on the characterization of the hydrographenes that are obtained from different types of graphite including synthetic graphite powder, natural flake graphite, and annealed graphite powder.Analysis by solid state C-13 NMR spectroscopy proved to be important since it was shown that the hydrographenes are composed of interior, isolated aromatic (predominantly fully substituted benzene) rings surrounded by saturated rings. The expected clusters of benzene rings were not found. NMR spectroscopy also offers strong evidence for the presence of tent-butyl alcohol and ethanol (workup solvent) that could not be removed in vacuo from the samples. These compounds could be observed to move freely within the layers of the hydrographene.High-resolution transmission electron microscopy images revealed a remarkable change in morphology that results when hydrogen is added to the graphenide. The appearance of edge and circular dislocations and increased distances between graphitic layers are most visible in the case of the hydrographenes that are formed from annealed graphite. The repetitive hydrogenation of synthetic graphite powder leads to an increase in the distances between the graphitic layers in the (002) direction from 3.4 angstrom for the initial graphite to 4.11 angstrom after the first reduction and to 4.29 angstrom after a third reduction of the same material. Defect-free graphite is formed when the hydrographenes are heated. The distance between carbon layers decreases from 4.11 to 3.44 angstrom after heating the samples to 1200 degrees C. This trend toward the spacing of graphite confirms the reversibility of the functionalization process. The C-H bonds have been broken yielding hydrogen, and the exposed carbon orbitals are in close enough proximity to have reverted to graphite.This Account introduces only a narrow area of materials chemistry, and many applications of graphene and its derivatives can be expected as researchers exploit this burgeoning field.

The Billups-Birch Reduction chemistry has been shown to functionalize single-walled carbon nanotubes (SWCNTs) without damaging the sidewalls, but has challenges in scalability. Currently published work uses a large mole ratio of Li to carbon atoms in the SWCNT (Li:C) to account for lithium amide formation, however this increases the cost and hazard of the reaction. We report here the systematic understanding of the effect of various parameters on the extent of functionalization using resonant Raman spectroscopy. Addition of 1-iodododecane yielded alkyl-functionalized SWCNTs, which were isolated by solvent extraction and evaporation, and purified by a hydrocarbon wash. The presence of SWCNT growth catalyst residue (Fe) was shown to have a strong adverse effect on SWCNT functionalization. Chlorination-based SWCNT purification reduced the amount of residual Fe, and achieve a maximum ID/IG ratio using a Li:C ratio of 6:1 in a reaction time of 30 min. This result is consistent with published literature requiring 20-fold mole equivalents of Li per mole SWCNT with a reaction time of over 12 h. This new understanding of the factors influencing the functionalization chemistry will help cut down material and process costs, and also increase the selectivity of the reaction toward the desired product.

The hydrogenation of commercial graphite using lithium/ammonia as the reducing agent and tert-butyl alcohol as a proton source was investigated. Characterization of the products after successive reductions of the same material by high-resolution transmission electron microscopy revealed a new material that was replete with edge and circular dislocations. Analysis by solid-state (13)C NMR spectroscopy indicates that after three reductions, the remaining aromatic rings appear to be interior benzene rings. NMR spectroscopy also offers strong evidence for the presence of small amounts of tert-butyl alcohol and ethanol (workup solvent) that could not be removed in vacuo from the samples. These compounds could be observed to move freely between the layers of the hydrographene.

Solid- and solution-state nuclear magnetic resonance (NMR) studies of six Ecuadorian asphaltenes have provided insight into using NMR to characterize asphaltenes. For these asphaltenes, free radicals prevent obtaining quantitatively meaningful H-1-C-13 cross-polarization magic angle spinning (CPMAS) spectra but facilitate obtaining meaningful carbon aromaticity values in direct polarization with C-13 pulse excitation. The benefit of studying any asphaltene by obtaining a series of CPMAS spectra with multiple contact times, rather than just a single contact time, is demonstrated. Analyzing the CPMAS and direct C-13 pulse spectra indicates that, on average, condensed aromatic ring systems become larger as the aromaticity increases, which seems more consistent with "island" than "archipelago" aromatic structures, just as recently proposed for asphaltenes. Solution-state two-dimensional (2D) H-1-C-13 heteronuclear single-quantum coherence (HSQC) spectra of the asphaltenes provide a wealth of structural information and are particularly useful for demonstrating that isolated methyl branches on alkyl chains are much more abundant than aromatic methyl groups. The prospect of using cryoprobes to obtain one-dimensional (ID) and 2D spectra with a much higher signal-to-noise ratio (S/N) allowing for a more detailed analysis of the less abundant structural environments is clearly attractive.

Covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) is an important tool for tailoring their properties for research purposes and applications. In this study, SWCNT samples were first functionalized by reductive alkylation using metallic lithium and 1-iodododecane in liquid ammonia. Samples of the alkyl-functionalized SWCNTs were then pyrolyzed under an inert atmosphere at selected temperatures between 100 and 500 °C to remove the addends. The extent of defunctionalization was assessed using a combination of thermogravimetric analysis, Raman measurements of the D, G, and radial breathing bands, absorption spectroscopy of the first- and second-order van Hove peaks, and near-IR fluorescence spectroscopy of (n,m)-specific emission bands. These measurements all indicate a substantial dependence of defunctionalization rate on nanotube diameter, with larger diameter nanotubes showing more facile loss of addends. The effective activation energy for defunctionalization is estimated to be a factor of ∼1.44 greater for 0.76 nm diameter nanotubes as compared to those with 1.24 nm diameter. The experimental findings also reveal the quantitative variation with functionalization density of the Raman D/G intensity ratio and the relative near-IR fluorescence intensity. Pyrolyzed samples show spectroscopic properties that are equivalent to those of SWCNTs prior to functionalization. The strong structure dependence of the defunctionalization rate suggests an approach for scalable diameter sorting of mixed SWCNT samples.

Abstract Diatoms were found in late Holocene age ice-core samples recovered from the Quelccaya Summit Dome in the tropical Andes of Peru and were imaged by environmental scanning electron microscopy and identified. Freshwater diatoms in the genera Hantzschia, Pinnularia, and Aulacoseira were the most common taxa in the samples and indicate a freshwater source for the material, which also is suggested by the presence of the freshwater alga Volvox. The overall species composition of the diatoms suggests that the majority of taxa originated from a high-elevation lake or wetland in the cordillera surrounding the ice cap. The abundant diatom valves, up to 70 µm in size, likely were transported to the ice via wind.

Using classical molecular dynamics method the reason of formation of diamond clusters into the amorphous carbon under electron irradiation was studied. It was shown that activation barrier of transition of graphite cluster to diamond cluster takes place only in a case of clusters with size more than 14 nm, whereas smaller clusters could be obtained only by a chemical functionalization of graphitic materials which is in a good agreement with our experimental data.

Electron irradiation of anthracite functionalized by dodecyl groups leads to recrystallization of the carbon network into diamonds. The diamonds range in size from ∼2 to ∼10 nm and exhibit {111} spacing of 2.1 Å. A bulk process consistent with bias-enhanced nucleation is proposed in which the dodecyl group provides hydrogen during electron irradiation. Recrystallization into diamond occurs in the hydrogenated graphitic subsurface layers. Unfunctionalized anthracite could not be converted into diamond during electron irradiation. The dependence of the phase transition pressure on cluster size was estimated, and it was found that diamond particles with a radius up to 20 nm could be formed.

Electronic and optoelectronic devices based on thin films of carbon nanotubes are currently limited by the presence of metallic nanotubes. Here we present a novel approach based on nanotube alkyl functionalization to physically remove the metallic nanotubes from such network devices. The process relies on preferential thermal desorption of the alkyls from the semiconducting nanotubes and the subsequent dissolution and selective removal of the metallic nanotubes in chloroform. The approach is versatile and is applied to devices post-fabrication.

Because of graphene's anticipated applications in electronics and its thermal, mechanical, and optical properties, many scientists and engineers are interested in this material. Graphene is an isolated layer of the π-stacked hexagonal allotrope of carbon known as graphite. The interlayer cohesive energy of graphite, or exfoliation energy, that results from van der Waals attractions over the interlayer spacing distance of 3.34 Å (61 meV/C atom) is many times weaker than the intralayer covalent bonding. Since graphene itself does not occur naturally, scientists and engineers are still learning how to isolate and manipulate individual layers of graphene. Some researchers have relied on the physical separation of the sheets, a process that can sometimes be as simple as peeling of sheets from crystalline graphite using Scotch tape. Other researchers have taken an ensemble approach, where they exploit the chemical conversion of graphite to the individual layers. The typical intermediary state is graphite oxide, which is often produced using strong oxidants under acidic conditions. Structurally, researchers hypothesize that acidic functional groups functionalize the oxidized material at the edges and a network of epoxy groups cover the sp2-bonded carbon network. The exfoliated material formed under these conditions can be used to form dispersions that are usually unstable. However, more importantly, irreversible defects form in the basal plane during oxidation and remain even after reduction of graphite oxide back to graphene-like material.As part of our interest in the dissolution of carbon nanomaterials, we have explored the derivatization of graphite following the same procedures that preserve the sp2 bonding and the associated unique physical and electronic properties in the chemical processing of single-walled carbon nanotubes. In this Account, we describe efficient routes to exfoliate graphite either into graphitic nanoparticles or into graphene without resorting to oxidation. Our exfoliation process involves the intercalation of lithium into bulk graphite to yield graphene sheets reduced by the lithium. We can alkylate the resulting graphite salt reductively using solubilizing dodecyl groups. By probe microscopy, we show that these groups are attached covalently only at the graphitic edges.

Highly exfoliated sulfonated graphene sheets (SGSs), an alternative to graphene oxide and graphene derivatives, were synthesized, characterized, and applied to liver cancer cells in vitro. Cytotoxicity profiles were obtained using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, WST-1[2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, and lactate dehydrogenase release colorimetric assays. These particles were found to be non-toxic across the concentration range of 0.1 to 10 μg/ml. Internalization of SGSs was also studied by means of optical and electron microscopy. Although not conclusive, high-resolution transmission and scanning electron microscopy revealed variant internalization behaviors where some of the SGS became folded and compartmentalized into tight bundles within cellular organelles. The ability for liver cancer cells to internalize, fold, and compartmentalize graphene structures is a phenomenon not previously documented for graphene cell biology and should be further investigated.

The objective of this workshop was to focus on new directions in carbon nanomaterial research, with a particular focus on new frontiers in nanotube alignment and applications of nanofluids. The first Carbon Nano Material Workshop was held at the Radisson Hotel, Rapid City, South Dakota, from October 30 to November 1, 2011, and was organized by Dr. G. P. “Bud” Peterson, Georgia Institute of Technology, and Dr. Haiping Hong, South Dakota School of Mines and Technology. More than 70 people from various government agencies, national labs, universities, and industries attended the workshop. The workshop agenda follows. The workshop included keynote plenary sessions and invited and contributed sessions, as well as a dedicated poster session of selected presentations assembled from an open call for papers.

Reduction of the graphenic edges of annealed nanodiamond by sodium in liquid ammonia leads to a nanodiamond salt that reacts with either alkyl or aryl halides by electron transfer to yield radical anions that dissociate spontaneously into free radicals and halide. The free radicals were observed to add readily to the aromatic rings of the annealed nanodiamond. Nanodiamonds functionalized by phenyl radicals were sulfonated in oleum, and the resulting sulfonic acid was converted to the sodium salt by treatment with sodium hydroxide. The solubility of the salt in water was determined to be 248 mg/L. Nanodiamond functionalized by carboxylic acid groups could be prepared by reacting 5-bromovaleric acid with the annealed nanodiamond salt. The solubility of the sodium carboxylate in water was found to be 160 mg/L.

: Nanodiamond particles possess extraordinary mechanical, electronic, thermal, and tribological properties and exhibit significant potential as components of novel multifunctional materials. However, processing of diamond nanoparticles for many applications is hampered by agglomeration and inhomogeneous dispersions in organic or aqueous solvents that are often used for these applications. The search for novel methods to process nanodiamonds is thus an important goal in materials science. In this study, we report a versatile, scalable synthesis of water-soluble nanodiamonds using a route similar to that demonstrated earlier for carbon nanotubes and graphene.

In this paper, we report the effort to prepare a stable su spension of carbon nanotube s in a hydro philic thermal transfer fluid with the motivation of enhancing its properties such as thermal conductivity and freezing point . The process of creating these fluid s involves the dispersion of carbon nanoparticles into the thermal transport fluid through intermittent sonication and the use of additives such as surfactants. I. Nomenclature