Here we report on the fabrication of reconfigurable and solution processable nanoscale biosensors with multisensing capability, based on single-walled carbon nanotubes (SWCNTs). Distinct DNA-wrapped (hence water-soluble) CNTs were immobilized from solution onto different prepatterned electrodes on the same chip, via a low-cost dielectrophoresis (DEP) methodology. The CNTs were functionalized with specific, and different, aptamer sequences that were employed as selective recognition elements for biomarkers indicative of stress and neuro-trauma conditions. Multiplexed detection of three different biomarkers was successfully performed, and real-time detection was achieved in serum down to physiologically relevant concentrations of 50 nM, 10 nM, and 500 pM for cortisol, dehydroepiandrosterone-sulfate (DHEAS), and neuropeptide Y (NPY), respectively. Additionally, the fabricated nanoscale devices were shown to be reconfigurable and reusable via a simple cleaning procedure. The general applicability of the strategy presented, and the facile device fabrication from aqueous solution, hold great potential for the development of the next generation of low power consumption portable diagnostic assays for the simultaneous monitoring of different health parameters.

Fatigue crack growth rates have been determined on standard specimens containing long cracks ( = 5-10 mm) and on specimens containing two-dimensional short cracks (=O.l(MSOrnm). Large differences have been observed indicating that at a given stress intensity factor short cracks propagate much faster than long cracks. Mouth opening displacement measurements for both specimen geometries have shown that the crack closure effect is largely responsible for the observed effect. These results are used to rationalize the behaviour of short cracks initiated from natural sites which were either graphite nodules or microshrinkage pores. The three-dimensional aspect of these natural small cracks is analysed and discussed in detail.

We have determined the black carbon concentration in three sets of ice core samples from the GISP2 (Greenland Ice Sheet Project 2) ice core. The major peaks in black carbon concentration between 320 and 330 A.D. correlate well with peaks in ammonium concentration and with the dips in electrical conductivity measurements (ECM), which allows us to identify extensive forest fires in this time period. The average black carbon concentration during the 320 to 330 A.D. decade is found to be 2.1 µg of black carbon per 1 kg of snow melt water. The current snow (1989 and 1990) from the GISP2 site shows an average black carbon concentration of about 2.0 µ/kg suggesting that the rate of black carbon deposition at the GISP2 Greenland site during 1989–1990 was about the same as 1670 years ago.

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Keywords: quinoxaline-walled deep cavitand, multi-walled carbon nanotubes, oxygen plasma treatment, gold nanoparticle, benzene.The unprecedented sensitivity and partial selectivity of quinoxaline-walled thioether-legged deep cavitand functionalized multiwall carbon nanotubes toward traces of benzene vapors is presented. The cavitand is grafted onto gold nanoparticle (Au-NP) decorated oxygen plasma treated multiwall carbon nanotubes (O-MWCNT) by a self-assembled monolayer process affording a product referred to as cav-Au-MWCNT. The reported technique is suitable for the mass production of hybrid nanomaterials at low cost. The cav-Au-MWCNT resistive gas sensor operates at room temperature and shows an outstanding performance toward traces of benzene vapors. The detection of 2.5 ppb of benzene in dry air is demonstrated with a limit of detection (LOD) near 600 ppt. For the first time, it is shown that a CNT nanomaterial can effectively sense the extremely harmful benzene molecule with higher sensitivity than toluene or o-xylene at the trace levels. The cavitand is well suited for binding benzene, which, being in close proximity to the MWCNT, affects its density of states (DOS) shifting the Fermi level away from the valence band. The binding of benzene is transduced in a diminution of 2 MWCNT conductance. Furthermore, the inclusion of benzene is fully reversible at room temperature, implying that the sensor can operate at very low power consumption.

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SummaryHere we report on the gas sensing properties of multiwalled carbon nanotubes decorated with sputtered Pt or Pd nanoparticles. Sputtering allows for an oxygen plasma treatment that removes amorphous carbon from the surface of the carbon nanotubes and creates oxygenated surface defects in which metal nanoparticles nucleate within a few minutes. The decoration with the 2 nm Pt or the 3 nm Pd nanoparticles is very homogeneous. This procedure is performed at the device level (i.e., for carbon nanotubes deposited onto sensor substrates) for many devices in one batch, which illustrates the scalability for the mass production of affordable nanosensors. The response to selected aromatic and non-aromatic volatile organic compounds, as well as pollutant gases has been studied. Pt- and Pd-decorated multiwalled carbon nanotubes show a fully reversible response to the non-aromatic volatile organic compounds tested when operated at room temperature. In contrast, these nanomaterials were not responsive to the aromatic compounds studied (measured at concentrations up to 50 ppm). Therefore, these sensors could be useful in a small, battery-operated alarm detector, for example, which is able to discriminate aromatic from non-aromatic volatile organic compounds in ambient.

Herein a strategy is presented for the assembly of both static and stimuli‐responsive single‐molecule heterostructures, where the distance and electronic coupling between an individual functional nanomoiety and a carbon nanostructure are tuned via the use of DNA linkers. As proof of concept, the formation of 1:1 nanohybrids is controlled, where single quantum dots (QDs) are tethered to the ends of individual carbon nanotubes (CNTs) in solution with DNA interconnects of different lengths. Photoluminescence investigations—both in solution and at the single‐hybrid level—demonstrate the electronic coupling between the two nanostructures; notably this is observed to progressively scale, with charge transfer becoming the dominant process as the linkers length is reduced. Additionally, stimuli‐responsive CNT‐QD nanohybrids are assembled, where the distance and hence the electronic coupling between an individual CNT and a single QD are dynamically modulated via the addition and removal of potassium (K+) cations; the system is further found to be sensitive to K+ concentrations from 1 pM to 25 × 10−3 m. The level of control demonstrated here in modulating the electronic coupling of reconfigurable single‐molecule heterostructures, comprising an individual functional nanomoiety and a carbon nanoelectrode, is of importance for the development of tunable molecular optoelectronic systems and devices.