Chemical sensors based on individual single-walled carbon nanotubes (SWNTs) are demonstrated. Upon exposure to gaseous molecules such as NO(2) or NH(3), the electrical resistance of a semiconducting SWNT is found to dramatically increase or decrease. This serves as the basis for nanotube molecular sensors. The nanotube sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature. Sensor reversibility is achieved by slow recovery under ambient conditions or by heating to high temperatures. The interactions between molecular species and SWNTs and the mechanisms of molecular sensing with nanotube molecular wires are investigated.

Density functional theory calculations are performed to unravel the nature of the contact between metal electrodes and monolayer MoS2. Schottky barriers are shown to be present for a variety of metals with the work functions spanning over 4.2-6.1 eV. Except for the p-type Schottky contact with platinum, the Fermi levels in all of the studied metal-MoS2 complexes are situated above the midgap of MoS2. The mechanism of the Fermi level pinning at metal-MoS2 contact is shown to be unique for metal-2D-semiconductor interfaces, remarkably different from the well-known Bardeen pinning effect, metal-induced gap states, and defect/disorder induced gap states, which are applicable to traditional metal-semiconductor junctions. At metal-MoS2 interfaces, the Fermi level is partially pinned as a result of two interface behaviors: first by a metal work function modification by interface dipole formation due to the charge redistribution, and second by the production of gap states mainly of Mo d-orbitals character by the weakened intralayer S-Mo bonding due to the interface metal-S interaction. This finding would provide guidance to develop approaches to form Ohmic contact to MoS2.

A novel nanomaterial which consists of graphene sheets decorated with silsesquioxane molecoles has been developed. Indeed, aminopropyl-silsesquioxane (POSS-NH 2 ) has been employed to functionalize graphene oxide sheets (GOs). The surface grafting of GOs with POSS-NH 2 has been established by infrared spectroscopy and X-ray photoelectron spectroscopy, while the morphology has been investigated by field emission electron microscopy as well as by atomic force microscopy. The combination of the amino functionalized POSS molecules with GO sheets produces a hybrid silicon/graphite-based nanomaterial, named GRAPOSS, for which the electrical conductivity of reduced GO was restored, thus allowing promising exploitations in several fields such as polymer nanocomposites.Supporting Information. Experimental procedures, AFM and XPS characterization of the prepared samples. This material is available free of charge via the Internet at

12Tunnel field effect transistors (TFETs) based on vertical stacking of two dimensional materials are 13 of interest for low-power logic devices. The monolayer transition metal dichalcogenides (TMDs) 14 with sizable band gaps show promise in building p-n junctions (couples) for TFET applications.

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Among the candidates to replace Li-ion batteries, Li-S cells are an attractive option as their energy density is about five times higher (~2,600 Wh kg). The success of Li-S cells depends in large part on the utilization of metallic Li as anode material. Metallic lithium, however, is prone to grow parasitic dendrites and is highly reactive to several electrolytes; moreover, Li-S cells with metallic Li are also susceptible to polysulfides dissolution. Here, we show that ~10-nm-thick two-dimensional (2D) MoS can act as a protective layer for Li-metal anodes, greatly improving the performances of Li-S batteries. In particular, we observe stable Li electrodeposition and the suppression of dendrite nucleation sites. The deposition and dissolution process of a symmetric MoS-coated Li-metal cell operates at a current density of 10 mA cm with low voltage hysteresis and a threefold improvement in cycle life compared with using bare Li-metal. In a Li-S full-cell configuration, using the MoS-coated Li as anode and a 3D carbon nanotube-sulfur cathode, we obtain a specific energy density of ~589 Wh kg and a Coulombic efficiency of ~98% for over 1,200 cycles at 0.5 C. Our approach could lead to the realization of high energy density and safe Li-metal-based batteries.

A detailed in situ infrared spectroscopy analysis of single layer and multilayered graphene oxide (GO) thin films reveals that the normalized infrared absorption in the carbonyl region is substantially higher in multilayered GO upon mild annealing. These results highlight the fact that the reduction chemistry of multilayered GO is dramatically different from the single layer GO due to the presence of water molecules confined in the ∼1 nm spacing between sheets. IR spectroscopy, XPS analysis, and DFT calculations all confirm that the water molecules play a significant role interacting with basal plane etch holes through passivation, via evolution of CO(2) leading to the formation of ketone and ester carbonyl groups. Displacement of water from intersheet spacing with alcohol significantly changes the chemistry of carbonyl formation with temperature.

Mechanical energy harvesters are needed for diverse applications, including self-powered wireless sensors, structural and human health monitoring systems, and the extraction of energy from ocean waves. We report carbon nanotube yarn harvesters that electrochemically convert tensile or torsional mechanical energy into electrical energy without requiring an external bias voltage. Stretching coiled yarns generated 250 watts per kilogram of peak electrical power when cycled up to 30 hertz, as well as up to 41.2 joules per kilogram of electrical energy per mechanical cycle, when normalized to harvester yarn weight. These energy harvesters were used in the ocean to harvest wave energy, combined with thermally driven artificial muscles to convert temperature fluctuations to electrical energy, sewn into textiles for use as self-powered respiration sensors, and used to power a light-emitting diode and to charge a storage capacitor.