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.

Chalcogenoxanthylium dyes were characterized as sensitizers of nanocrystalline titania in dye-sensitized solar cells (DSSCs). Four series of dyes were characterized: 2,7-bis(dimethylamino)-9-(2-thienyl-5-carboxy)chalcogenoxanthylium dyes (1-E, where E ) O, S, Se); 2,7-bis(dimethylamino)-9-(3-thienyl-2-carboxy)chalcogenoxanthylium dyes (2-E, where E ) S, Se); a 2,7-bis(dimethylamino)-9-(2-thienyl)selenoxanthylium dye (3-Se); 4-Se, a constrained analog of 1-Se. The orientation and aggregation state of the dyes were controlled by varying the position of the surface-attachment group relative to the xanthylium core. Series 1 dyes and 4-Se underwent H-aggregation on titania surfaces, whereas series 2 dyes adsorbed in amorphous monolayers.(3-Se did not adsorb appreciably to titania films, due to the lack of a tethering group.) The H-aggregated dyes exhibited broader absorption bands, increased light-harvesting efficiencies, and improved photoelectrochemical performance compared to the dyes which adsorbed in amorphous monolayers. The maximum incident photonto-current efficiencies (IPCEs) of series 1 dyes ranged from 70% to 84%, whereas those of 2-S and 2-Se were 11% and 20%. Our findings reveal that the light-harvesting efficiency, IPCE, and absorbed photon-tocurrent efficiency (APCE) of DSSCs with organic dyes can be optimized by systematically varying the structure of the dyes and their orientation and aggregation state on the surface.

In situ high-pressure Raman spectroscopy, with corroborating density functional calculations, is used to probe C-H chemical bonds formed when dissociated hydrogen diffuses from a platinum nanocatalyst to three distinct graphenic surfaces. At ambient temperature, hydrogenation and dehydrogenation are reversible in the combined presence of an active catalyst and oxygen heteroatoms. Hydrogenation apparently occurs through surface diffusion in a chemisorbed state, while dehydrogenation requires diffusion of the chemisorbed species back to an active catalyst.

This study reports 6FDA:BPDA-DAM polyimidederived hollowf iber carbon molecular-sieve (CMS) membranes for hydrogen and ethylene separation. Since H 2 /C 2 H 4 selectivity is the lowest among H 2 /(C 1 -C 3 )h ydrocarbons,a n optimizedC MS fiber for this gas pair is useful for removing hydrogen from all-cracked gas mixtures.Aprocess we term hyperaging provides highly selective CMS fiber membranes by tuning CMS ultramicropores to favor H 2 over larger molecules to give aH 2 /C 2 H 4 selectivity of over 250. Hyperaging conditions and ah yperaging mechanism are discussed in terms of an expedited physical aging process,w hich is largely controlled by the hyperaging temperature.F or the specific CMS material considered here,ahyperaging temperature beyond 90 8 8Cbut less than 250 8 8Cworks best. Hyperaging also stabilizes CMS materials against physical aging and stabilizes the performance of H 2 separation over extended periods.This work opens ad oor in the development of CMS materials for the separation of small molecules from large molecules.

In the next decade, separation science will be an important research topic in addressing complex challenges like reducing carbon footprint, lowering energy cost, and making industrial processes simpler. In industrial chemical processes, particularly in petrochemical operations, separation and product refining steps are responsible for up to 30% of energy use and 30% of the capital cost. Membranes and adsorption technologies are being actively studied as alternative and partial replacement opportunities for the state-of-the-art cryogenic distillation systems. This paper provides an industrial perspective on the application of membranes in industrial petrochemical cracker operations. A gas separation performance figure of merit for propylene/propane separation for different classes of materials ranging from inorganic, carbon, polymeric, and facilitated transport membranes is also reported. An in-house–developed model provided insights into the importance of operational parameters on the overall membrane design.

Deposition techniques that can uniformly and conformally coat deep trenches and very high aspect ratio pores with uniform thickness fi lms are valuable in the synthesis of complex three-dimensionally structured materials. Here it is shown that high pressure chemical vapor deposition can be used to deposit conformal fi lms of II-VI semiconductors such as ZnSe, ZnS, and ZnO into high aspect ratio pores. Microstructured optical fi bers serve as tailored templates for the patterning of II-VI semiconductor microwire arrays of these materials with precision and fl exibility. In this way, centimeters-long microwires with exterior surfaces that conform well to the nearly atomically smooth silica templates can be fabricated by conformal coating. This process allows for II-VI semiconductors, which cannot be processed into optical fi bers with conventional techniques, to be fabricated into step index and microstructured optical fi bers.

MQ silicone copolymers (MQ resins) and polyethylenes are very important polymers that are used in our daily lives. The microstructures of these polymers dictate some of their important physical properties and applications. However, it remains a challenge to accurately and quantitatively measure microstructural information by NMR due to an acoustic ringing baseline curvature observed with state-of-the-art high-sensitivity helium-cooled NMR cryoprobes. In this work, we report spin echo 90_180 NMR pulse sequences, with adiabatic and hard 180°pulse versions and different delays before and after the 180°pulse, that attenuate acoustic ringing artefacts and the 29 Si strong background signal from cryoprobe construction materials. An appropriate methodology to quantitatively measure M (Me 3 SiO 1/2 ), T(OZ) [Si(OZ)O 3/2 ], and Q (SiO 4/2 ) structural information of MQ resins (where Z may be H, Na, or iPr), and quantitatively measure the comonomer content information in polyethylene and polyethylene blends, is presented.

The ability to manipulate a single quantum object, such as a single electron or a single spin, to induce a change in a macroscopic observable lies at the heart of nanodevices of the future. We report an experiment wherein a single superconducting flux quantum, or a fluxon, can be exploited to switch the resistance of a nanowire between two discrete values. The experimental geometry consists of centimeter-long nanowires of superconducting Ga-In eutectic, with spontaneously formed Ga nanodroplets along the length of the nanowire. The nonzero resistance occurs when a Ga nanodroplet traps one or more superconducting fluxons, thereby driving a Josephson weak-link created by a second nearby Ga nanodroplet normal. The fluxons can be inserted or flipped by careful manipulation of the magnetic field or temperature to produce one of many metastable states of the system.