Arrays of electrical devices with each comprising multiple single-walled carbon nanotubes (SWNT) bridging metal electrodes are obtained by chemical vapor deposition (CVD) of nanotubes across prefabricated electrode arrays. The ensemble of nanotubes in such a device collectively exhibits large electrical conductance changes under electrostatic gating, owing to the high percentage of semiconducting nanotubes. This leads to the fabrication of large arrays of low-noise electrical nanotube sensors with 100% yield for detecting gas molecules. Polymer functionalization is used to impart high sensitivity and selectivity to the sensors. Polyethyleneimine coating affords n-type nanotube devices capable of detecting NO 2 at less than 1 ppb (parts-per-billion) concentrations while being insensitive to NH 3 . Coating Nafion (a polymeric perfluorinated sulfonic acid ionomer) on nanotubes blocks NO 2 and allows for selective sensing of NH 3 . Multiplex functionalization of a nanotube sensor array is carried out by microspotting. Detection of molecules in a gas mixture is demonstrated with the multiplexed nanotube sensors.

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Metallic and semiconducting carbon nanotubes generally coexist in as-grown materials. We present a gas-phase plasma hydrocarbonation reaction to selectively etch and gasify metallic nanotubes, retaining the semiconducting nanotubes in near-pristine form. With this process, 100% of purely semiconducting nanotubes were obtained and connected in parallel for high-current transistors. The diameter- and metallicity-dependent "dry" chemical etching approach is scalable and compatible with existing semiconductor processing for future integrated circuits.

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Herein, we demonstrate a ternary ionic hydrogel sensor consisting of tannic acid, sodium alginate, and covalent cross-linked polyacrylamide as skin-mountable and wearable sensors. Based on the multiple weak H-bonds and synergistic effects between the three components, the as-prepared hybrid hydrogel exhibits ultrastretchability with high elasticity, good self-healing, excellent conformability, and high self-adhesiveness to diverse substrates both in air and underwater. More importantly, the ternary hydrogel exhibits high strain sensitivity especially under subtle strains with a gauge factor of 2.0, which is close to the theoretical value of the ionic hydrogel sensors; an extremely large workable range of strain (0.05–2100%); and a low operating voltage 0.07 V. Consequently, the sensor demonstrates superior sensing performance for real-time monitoring of the large and subtle human motions, including limb motions, swallowing, smiling, and wrist pulse. Therefore, it is believed that the STP hydrogel has great potential applications in health monitoring, smart wearable devices, and soft robots.

With a cut metallic SWNT (gap L ~ 5-6 nm) bridged by a pentacene nano-crystallite (Fig.1b&c), we observed clear semiconducting FET characteristics in the current vs. gate (I ds -V gs ) curve (Fig. 2a). The device exhibited a current modulation of I max /I min ~ 10 5 under gating at a fixed bias voltage of V ds = -0.5V. The drastic switching clearly differed from the original metallic SWNT device (lack of gate dependence, Fig. 2a inset). This corresponds to the formation of a pentacene FET with channel length L ~ 5-6 nm and width of w ~ 2 nm (i.e., the diameter of the SWNT) as charge transport via hopping between pentacene molecules should be mainly confined in a width on the order of the tube diameter. Notably, the subthreshold swing of the device is S ~ 400 mV/decade (Fig. 2a).Small organic molecules and conjugated polymers can be easily processed to afford functional electronics such as field effect transistors (FETs), 1a and in principle, scaling 1b to singlemolecule long devices could circumvent the low carrier mobility problem for these materials to afford high performance ballistic FETs 2,3 . For highly scaled molecular transistors with short channels however, it is crucial to develop novel device geometries to optimize gate electrostatics needed for ON/OFF switching. 4,5 It is shown here that single-walled carbon nanotubes (SWNT) can be used as quasi one-dimensional (1D) electrodes to construct organic FETs with molecular scale width (~2 nm) and channel length (down to 1-3 nm). The favorable gate electrostatics associated with the sharp 1D electrode geometry allows for room temperature conductance modulation by orders of magnitude for organic transistors that are only several-molecules in length, with switching characteristics superior to devices with lithographically patterned metal electrodes. We suggest that carbon nanotubes may prove to be novel electrodes for a variety of molecular devices.We first developed a reproducible method of cutting metallic SWNTs to form small gaps within the tubes and with control over the gap size down to L~2 nm. The cutting relied on electrical break-down 6 of individual SWNTs between two metal electrodes (Fig. 1a), and the size of the cut was found to be controllable by varying the lengths of the SWNTs (see Ref.6b and Supp. Info). Organic materials were then deposited to bridge the gap in the vapor (for pentacene) or solution phase (for regio-regular ploy (3-hexylthiophene), P3HT), forming the smallest organic FETs with effective channel length down to L~1-3 nm and width ~2 nm. b cWe varied the channel lengths L of SWNT-contacted pentacene FETs (L ~ 1-3 nm, L ~5-6 nm and L ~10-15 nm respectively) and observed length dependent transport properties at various temperatures. At T=300K, the devices exhibited on-current I max scaling approximately with ~1/L (under V ds =-1 V). This suggests

We present a systematic experimental investigation of the reactions between hydrogen plasma and single-walled carbon nanotubes (SWNTs) at various temperatures. Microscopy, infrared (IR) and Raman spectroscopy, and electrical transport measurements are carried out to investigate the properties of SWNTs after hydrogenation. Structural deformations, drastically reduced electrical conductance, and an increased semiconducting nature of SWNTs upon sidewall hydrogenation are observed. These changes are reversible upon thermal annealing at 500 degrees C via dehydrogenation. Harsh plasma or high temperature reactions lead to etching of nanotubes likely via hydrocarbonation. Smaller SWNTs are markedly less stable against hydrocarbonation than larger tubes. The results are fundamental and may have implications to basic and practical applications including hydrogen storage, sensing, band gap engineering for novel electronics, and new methods of manipulation, functionalization, and etching of nanotubes.

Manganese MOF-based cathodes achieve high discharge capacity, reduced overpotentials and promoted reversibility in Li–CO2batteries.