Low-dimensional carbon nanomaterials such as fullerenes, nanotubes, graphene and diamondoids have extraordinary physical and chemical properties. Compression-induced polymerization of aromatic molecules could provide a viable synthetic route to ordered carbon nanomaterials, but despite almost a century of study this approach has produced only amorphous products. Here we report recovery to ambient pressure of macroscopic quantities of a crystalline one- dimensional sp(3) carbon nanomaterial formed by high-pressure solid-state reaction of benzene. X-ray and neutron diffraction, Raman spectroscopy, solid-state NMR, transmission electron microscopy and first-principles calculations reveal close- packed bundles of subnanometre-diameter sp(3)-bonded carbon threads capped with hydrogen, crystalline in two dimensions and short-range ordered in the third. These nanothreads promise extraordinary properties such as strength and stiffness higher than that of sp(2) carbon nanotubes or conventional high-strength polymers. They may be the first member of a new class of ordered sp(3) nanomaterials synthesized by kinetic control of high-pressure solid-state reactions.

The ionicity and transport properties of a series of diethylmethylamine (DEMA) based protic ionic liquids (PILs) were characterized, principally utilizing nuclear magnetic resonance (NMR) spectroscopy. PILs were formed via the protonation of DEMA by an array of acids spanning a large range of acidities. A correlation between the (1)H chemical shift of the exchangeable proton and the acidity of the acid used for the synthesis of the PIL was observed. The gas phase proton affinity of the acid was found to be a better predictor of the extent of proton transfer than the commonly used aqueous ΔpKa. Pulsed field gradient (PFG) NMR was used to determine the diffusivity of the exchangeable proton in a subset of the PILs. The exchangeable proton diffuses with the acid if the PIL is synthesized with a weak acid, and with the base if a strong acid is used. The ionicity of the PILs was characterized using the Walden analysis and by comparing to the ideal Nernst-Einstein conductivity predicted from the (1)H PFG-NMR results.

As ligand functionalization of nanomaterials becomes more complex, methods to characterize the organization of multiple ligands on surfaces is required. In an effort to further the understanding of ligand-surface interactions, a combination of multinuclear ((1)H, (29)Si, (31)P) and multidimensional solid-state nuclear magnetic resonance (NMR) techniques was utilized to characterize the phosphonic acid functionalization of fumed silica nanoparticles using methylphosphonic acid (MPA) and phenylphosphonic acid (PPA). (1)H → (29)Si cross-polarization (CP)-magic angle spinning (MAS) solid-state NMR was used to selectively detect silicon atoms near hydrogen atoms (primarily surface species); these results indicate that geminal silanols are preferentially depleted during the functionalization with phosphonic acids. (1)H → (31)P CP-MAS solid-state NMR measurements on the functionalized silica nanoparticles show three distinct resonances shifted upfield (lower ppm) and broadened compared to the resonances of the crystalline ligands. Quantitative (31)P MAS solid-state NMR measurements indicate that ligands favor a monodentate binding mode. When fumed silica nanoparticles were functionalized with an equal molar ratio of MPA and PPA, the MPA bound the nanoparticle surface preferentially. Cross-peaks apparent in the 2D (1)H exchange spectroscopy (EXSY) NMR measurements of the multiligand sample at short mixing times indicate that the MPA and PPA are spatially close (≤5 Å) on the surface of the nanostructure. Furthermore, (1)H-(1)H double quantum-single quantum (DQ-SQ) back-to-back (BABA) 2D NMR spectra further confirmed that MPA and PPA are strongly dipolar coupled with observation of DQ intermolecular contacts between the ligands. DQ experimental buildup curves and simulations indicate that the average distance between MPA and PPA is no further than 4.2 ± 0.2 Å.

The molecular interactions of silk materials plasticized using glycerol were studied, as these materials provide options for biodegradable and flexible protein-based systems. Plasticizer interactions with silk were analyzed by thermal, spectroscopic, and solid-state NMR analyses. Spectroscopic analysis implied that glycerol was hydrogen bonded to the peptide matrix, but may be displaced with polar solvents. Solid-state NMR indicated that glycerol induced β-sheet formation in the dried silk materials, but not to the extent of methanol treatment. Fast scanning calorimetry suggested that β-sheet crystal formation in silk-glycerol films appeared to be less organized than in the methanol treated silk films. We propose that glycerol may be simultaneously inducing and interfering with β-sheet formation in silk materials, causing some improper folding that results in less-organized silk II structures even after the glycerol is removed. This difference, along with trace residual glycerol, allows glycerol extracted silk materials to retain more flexibility than methanol processed versions.

Catechol on TiO 2 is a model system for a class of molecules that bind and interact very strongly with metal oxides. This interaction gives rise to a marked charge-transfer absorption band that can be used to sensitize the complex to visible light. In solar cells, these are called type II sensitizers in contrast with type I sensitizers where an excitation of the molecule with subsequent charge injection is the main mechanism for placing an electron in the conduction band of the semiconductor. The adsorption geometry of these molecules is critical in their functioning. Nuclear magnetic resonance (NMR) spectroscopic methods can be used to elucidate structural information about the local geometry at the substrate−molecule interface. NMR methods coupled with density functional theory (DFT) allow for the detailed characterization of molecular binding modes. In the present work, we report a solid-state NMR and DFT study of catechol on TiO 2 . DFT-GIPAW chemical shift predictions for the 13 C CP-MAS experiments unambiguously indicate the presence of a chelated geometry. 1 H → 13 C cross-polarization build-up kinetics were used to determine the protonation state of additional geometries and point toward the presence of molecular species. The most stable adsorption modes on regular slab models were found to be bidentate, and it is only in the presence of defective surfaces where the chelated mode is stabilized in the presence of undercoordinated titanium surface sites. The combined NMR and DFT approach thus allows characterization of the binding geometry, which is a stepping stone in the design of more complex light-harvesting architectures. This work constitutes, to the best of our knowledge, the first detailed instance of combined solid-state NMR and DFT studies on this class of materials.

Silicon clathrates contain cage‐like structures that can encapsulate various guest atoms or molecules. An electrochemical evaluation of type I silicon clathrates based on Ba8AlySi46−y as the anode material for lithium‐ion batteries is presented here. Postcycling characterization with nuclear magnetic resonance and X‐ray diffraction shows no discernible structural or volume changes even after electrochemical insertion of 44 Li (≈1 Li/Si) into the clathrate structure. The observed properties are in stark contrast with lithiation of other silicon anodes, which become amorphous and suffer from large volume changes. The electrochemical reactions are proposed to occur as single phase reactions at approximately 0.2 and 0.4 V versus Li/Li+ during lithiation and delithiation, respectively, distinct from diamond cubic or amorphous silicon anodes. Reversible capacities as high as 499 mAh g−1 at a 5 mA g−1 rate were observed for silicon clathrate with composition Ba8Al8.54Si37.46, corresponding to ≈1.18 Li/Si. These results show that silicon clathrates could be promising durable anodes for lithium‐ion batteries.

The composition of the Sutter's Mill meteorite insoluble organic material was studied both in toto by solid-state NMR spectroscopy of the powders and by gas chromatography-mass spectrometry analyses of compounds released upon their hydrothermal treatment. Results were compared with those obtained for other meteorites of diverse classifications (Murray, GRA 95229, Murchison, Orgueil, and Tagish Lake) and found to be so far unique in regard to the molecular species released. These include, in addition to Ocontaining aromatic compounds, complex polyether-and estercontaining alkyl molecules of prebiotic appeal and never detected in meteorites before. The Sutter's Mill fragments we analyzed had likely been altered by heat, and the hydrothermal conditions of the experiments realistically mimic early Earth settings, such as near volcanic activity or impact craters. On this basis, the data suggest a far larger availability of meteoritic organic materials for planetary environments than previously assumed and that molecular evolution on the early Earth could have benefited from accretion of carbonaceous meteorites both directly with soluble compounds and, for a more protracted time, through alteration, processing, and release from their insoluble organic materials.carbonaceous chondrites | extraterrestrial organic materials

Excluding aqueous solutions, the highest ambient temperature conductivities of lithium containing materials have been found, not in liquid, but in glassy, mixed glass-crystal and crystal phases. The partly recrystallized thiophosphate glass reported by Tatsumisago and co-workers [3] exhibited an ambient temperature conductivity of a remarkable 17 mS cm −1 , significantly higher than the highest reported in nonaqueous electrolyte solutions, and that has now been exceeded by a chlorinecontaining variant of the Kamaya et al. thiophosphogermanate superionic crystal [4] that exhibits σ 25 °C = 25 mS cm −1 . [5] Part of the success of these solid electrolytes is due to the fact that the alkali cation is now, not only the most mobile ion, but usually the only mobile ion. However, as rigid materials, they tend to be mechanically fragile and are prone to encounter junction problems with anode and cathode materials. Excellent cell performance has nonetheless been reported. [5] An alternative approach that avoids the liquid state is to dissolve salts in plastic crystal phases. Two types of plastic crystal solvents have been explored: (i) molecular solvent [6,7] (succinonitrile (SSN) in which a salt like LiN(Tf) 2 is dissolved) and (ii) organic cation salts in which salts like LiBF 4 and LiN(Tf) 2 are dissolved, of which many variants [8][9][10] have been employed. Although it was not mentioned in the initial publication, [6] the success of the plastic crystal state as a solvent lies primarily in the ability of the molecular solvent (or molecular ions), to reorient on short time scales (t reor ≈0.1 ns in the case of SSN [11] ) thus providing a high entropy medium within which the ions enjoy high mobility. While each case has been considered successful, the disadvantage of each is that the Li + species proves to be the least mobile species. This is because, due to its high charge radius ratio, the Li cation dominates competition for ligands and "digs itself a hole" in the same way as it does in a typical nonaqueous molecular liquid electrolyte. A consequence is low mobility of the electroactive species relative to others, and consequent polarization problems during operation at high currents.It is against this backdrop that we have sought to develop an improved type of ambient temperature plastic crystal ion conductor, one in which the only mobile species is the alkali cation so that (as in superionic glasses and crystals) the conductivity Portable electronic devices are predominantly powered by lithium ion batteries in which the electrolyte is a liquid or gel of lithium salts dissolved in molecular solvents. There have been many attempts to replace the flammable liquid component of the electrolyte by alternative alkali metal transporting media, such as superionic crystals, alkali-conducting glassy solids, ionic liquids, saltin-molecular plastic crystal solvent, and salt-in-ionic plastic crystal solvents. Except for the first two of the above, which have their own problems, all the above have the disadvantage that the alkali ...