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The language spoken in La Vis is a constructed language. It is both recognizable and unrecognizable; it gives credibility to the characters and to the whole décor. Reality is elusive and yet believable. Perceived as a multilayered language, it is reduced to one single word in the final sequence.

High-purity semiconducting single-walled carbon nanotubes (sc-SWCNTs) are promising for portable and high-sensitivity gas sensors because of their excellent physical and electrical properties. Here, we describe the synthesis of a novel indigo-fluorene-based copolymer (PFIDBoc) that has been designed to selectively enrich sc-SWCNTs with excellent purity (>99.9%) yet contain a latent function in the form of a tert-butoxy (t-BOC)-protected amine that can be later revealed and exploited for carbon dioxide (CO₂) gas sensing. SWCNTs wrapped with the PFIDBoc polymer can be easily converted via an on-chip thermal process to reveal a vinylogous amide moiety with a secondary amine nitrogen within the indigo building block of the copolymer which is perfectly suited for CO₂ recognition. Thin-film transistors and sensors were inkjet-printed onto rigid and flexible substrates, demonstrating the versatility of enriched PFIDBoc-derived sc-SWCNT dispersions. The printed transistors exhibited a mobility up to 9 cm² V⁻¹ s⁻¹ and on/off current ratios >10⁵. We further demonstrate herein a CO₂ sensor for indoor air quality monitoring even in low humidity environments, possessing a linear response with up to ∼5.4% sensitivity and a dynamic range between 400 and 2000 ppm in air with a relative humidity of ∼ 40%.

The story unfolds chronologically and each sequence has a specific ‘time quality’ according to who appears on-screen. The death of the grandmother evokes the past, while most of the story takes place in the present as told by the omniscient camera. The future brings a paradoxical sense of closure.

Dispersions of purely semiconducting single-walled carbon nanotubes (SWCNTs) have enabled solution-processed SWCNT networks as active layers in field-effect transistors (FETs) with high carrier mobilities and excellent on/off current ratios. Although reproducibility has improved in recent years, reaching the level that is required for commercial large-scale processing remains a challenge. A key issue is the tendency of SWCNTs to aggregate over time, resulting in network inhomogeneities that cause large device performance variations. Based on the tailored formulation of colloidal inks by the choice of solvent and use of additives, we demonstrate the strong stabilization effect of phenanthroline additives on polymer-sorted (6,5) SWCNT using time-dependent near-infrared absorption spectroscopy as a fast and simple assessment tool for the aggregation rate. The addition of the N-heteropolycycle 1,10-phenanthroline significantly extends the stability of dispersions of polymer-wrapped nanotubes in toluene and hence improves the morphology of spin-coated networks even after ink storage for several days. Bottom-contact, top-gate FETs based on such networks show much higher charge carrier mobilities and drastically reduced device-to-device variations compared to devices based on SWCNT dispersions without phenanthroline. Nanotube ink formulations with small-molecule additives are an important step toward reproducible device parameters and are crucial for the translation of nanotube FETs from the laboratory to commercial applications.

The high sensitivity of carbon nanotube devices as gas sensors is generally attributed to the large surface area of the material, whereas selectivity is often imparted by the “lock-and-key” mechanism. In contrast with this picture, where little function is conferred to the underlying substrate, we demonstrate that bottom gate carbon nanotube network field-effect transistors (CNN-FETs) fabricated on a variety of polymer dielectrics, but with the same pristine carbon nanotubes, show differentiated responses to analytes. Interaction with the environment thus occurs not only directly with carbon nanotubes but is often mediated by the substrate. In a broad survey of polymers, we identify several materials suitable as the gate dielectric of printed devices and that yield a vanishing gate hysteresis in ambient air. The other two classes of polymers that induce a lagging or advancing hysteresis in CNN-FETs are found desirable for gas sensing applications. Moreover, we have tested CNN-FETs with different polymer gate dielectrics against a series of analytes ranging from common alcohols to organic solvents and amines, among others. A rich set of distinct and complementary analyte signatures could be observed, identifying the polymer gate dielectric as a differentiator for chemical discrimination in a future printed cross-reactive sensor array, that is, an electronic nose.

Although carbon nanotube transistors present outstanding performances based on key metrics, large-scale uniformity and repeatability required in printable electronics depend greatly on proper control of the electrostatic environment. Through a survey of polymer dielectric encapsulants compatible with printing processes, a simple correlation is found between the measured interfacial charge density and the onset of conduction in a transistor, providing a rational route to control the electrical characteristics of carbon nanotube transistors. Smooth and continuous balancing of the properties between unipolar p-type and n-type transport is achieved using a molar fraction series of poly(styrene-co-2-vinylpyridine) statistical copolymers combined with an electron-donating molecule. We further demonstrate the easy fabrication of a p-n diode which shows a modest rectification of 8:1.

To fully actualize the potential of boron nitride nanotubes (BNNTs), it is necessary to overcome the inherent insolubility of this nanomaterial. Drawing on the successes realized in the analogous carbon nanotube field, noncovalent functionalization with conjugated polymers offers a simple, scalable route toward the production of stable dispersions of BNNTs. 2,7-carbazoles were chosen as our core monomer based on density functional theory (DFT) predictions, which suggest superior interactions with BNNTs when compared to fluorene-BNNT interactions. Homo poly(2,7-carbazole)s and copolymers with fluorenes were synthesized and used successfully to disperse BNNTs into organic solvents. Thermogravimetric analysis and atomic force microscopy results confirm the proficiency of these polymers to disperse large amounts (> 80% by weight) of individualized BNNTs. Analysis of absorbance data shows that the choice of solvent is critical, with stability enhanced in THF compared to CHCl₃ due to the more efficient planarization of polymer chains on the surface of BNNTs, particularly for the homopolymers. The utility of these highly-soluble poly(2,7-carbazole)-BNNT complexes for printed electronics and transparent composites was demonstrated by the fabrication of simple capacitors and incorporation into poly(methyl methacrylate) composites, respectively.

A generalization of the Raman scattering (RS) spectrum, the Raman excitation map (REM) is a hyperspectral two-dimensional (2D) data set encoding vibrational spectra, electronic spectra and their coupling. Despite the great potential of REM for optical sensing and characterization with remarkable sensitivity and selectivity, the difficulty of obtaining maps and the length of time required to acquire them has been practically limiting. Here we show, with a simple setup using current optical equipment, that maps can be obtained much more rapidly than before (~ms to ~100 s now vs. ~1000 s to hours before) over a broad excitation range (here ~100 nm is demonstrated, with larger ranges straightforward to obtain), thus taking better advantage of scattering resonance. We obtain maps from different forms of carbon: graphite, graphene, purified single walled carbon nanotubes (SWCNTs) and chirality enriched SWCNTs. The relative speed and simplicity of the technique make REM a practical and sensitive tool for chemical analysis and materials characterization.

3D printing has enabled materials, geometries and functional properties to be combined in unique ways otherwise unattainable via traditional manufacturing techniques, yet its adoption as a mainstream manufacturing platform for functional objects is hindered by the physical challenges in printing multiple materials. Vat polymerization offers a polymer chemistry-based approach to generating smart objects, in which phase separation is used to control the spatial positioning of materials and thus at once, achieve desirable morphological and functional properties of final 3D printed objects. This study demonstrates how the spatial distribution of different material phases can be modulated by controlling the kinetics of gelation, cross-linking density and material diffusivity through the judicious selection of photoresin components. A continuum of morphologies, ranging from functional coatings, gradients and composites are generated, enabling the fabrication of 3D piezoresistive sensors, 5G antennas and antimicrobial objects and thus illustrating a promising way forward in the integration of dissimilar materials in 3D printing of smart or functional parts., 3D printing has enabled materials, geometries and functional properties to be combined in unique ways but printing multiple materials remains challenging. Here, the authors demonstrate how spatial distribution of different material phases can be modulated by controlling the kinetics of gelation, cross-linking density and material diffusivity in vat polymerization.

We describe a technique to prepare ensembles of neat, unbundled single-walled carbon nanotubes decorated with pure size-filtered metal nanoparticles. Polymer-encased nanotubes are drop-cast on nanoporous transmission electron microscope membrane grids, mounted within a nanoparticle-deposition apparatus, baked in situ to remove the polymer coating, and exposed to a beam of pure size-selected metal nanoparticles. Subsequent electron microscopy imaging reveals the presence of nanoparticles supported by pure suspended single-walled nanotubes. This method is promising for efficient production of prototype chemical and physical devices which require the presence of clean well-defined nanoparticle-nanotube hybrids for characterization, imaging, and applications.

Conjugated polymer extraction (CPE) is a low-cost, scalable process that can enrich single-walled carbon nanotube (SWCNT) materials in organic media. For other separation methods in aqueous phases, redox chemistry and/or pH control dramatically affect the sorting process of the SWCNTs. We have previously determined that the CPE process can be fine-tuned by adjusting the pH on the tube surface. Here, we systematically studied the effect of redox chemistry on the CPE process by adding organic p-/n-dopants. At a very strong p-/n-doping level, static repulsions dominated the interactions between the tubes and the CPE lost selectivity. When the doping level changed from a medium p-doping to a neutral state, the yield of CPE increased and the selectivity was compromised. We also observed chiral selectivity when a weak p-dopant was used. A photoluminescence excitation mapping under different titration conditions provided more insight into the doping level of the tubes relative to their diameters, chiralities, and redox potentials. We proposed a mechanism for the CPE process. The semiconducting and metallic tubes are separated because of their different solubilities, which are determined by the bundling energy between the tubes and are related to their doping level in polymer solutions.

Conjugated polymer extraction (CPE) has been shown to be a highly effective method to isolate high-purity semiconducting single-walled carbon nanotubes (sc-SWCNTs). In both literature reports and industrial manufacturing, this method has enabled enrichment of sc-SWCNTs with high purity (≥99.9%). High selectivity is typically obtained in nonpolar aromatic solvents, yet polar solvents may provide process improvements in terms of yield, purity and efficiency. Using an amphiphilic fluorene-alt-pyridine conjugated copolymer with hydrophilic side chains, we have investigated the enrichment of sc-SWCNTs in polar solvents. Various conditions such as polymer/SWCNT ratio, solvent polarity, solvent dielectric constant as well as polymer solubility and SWCNT dispersibility were explored in order to optimize the purity and yield of the enriched product. Herein, we provide insights on CPE by demonstrating that a conjugated polymer having a hydrophobic backbone and hydrophilic oligo(ethylene oxide) side chains provides near full recovery (95%) of sc-SWCNTs using a multiextraction protocol. High purity is also obtained, and differences in chiral selectivity compared to analogous hydrophobic systems were confirmed by optical absorption and Raman spectroscopy as well as photoluminescence excitation mapping. Taking into consideration the solvent dielectric constant, polarity index as well as polymer solubility and SWCNT dispersibility provides a better understanding of structure–property effects on sc-SWCNT enrichment. The resulting hydrophilic SWCNT dispersions demonstrate long-term colloidal stability, making them suitable for ink formulation and high-performance thin-film transistors fabrication.

Semiconducting single-walled carbon nanotubes (sc-SWCNTs) are emerging as a promising material for high-performance, high-density devices as well as low-cost, large-area macroelectronics produced via additive manufacturing methods such as roll-to-roll printing. Proof-of-concept demonstrations have indicated the potential of sc-SWCNTs for digital electronics, radiofrequency circuits, radiation hard memory, improved sensors, and flexible, stretchable, conformable electronics. Advances toward commercial applications bring numerous opportunities in SWCNT materials development and characterization as well as fabrication processes and printing technologies. Commercialization in electronics will require large quantities of sc-SWCNTs, and the challenge for materials science is the development of scalable synthesis, purification, and enrichment methods. While a few synthesis routes have shown promising results in making near-monochiral SWCNTs, gram quantities are available only for small-diameter sc-SWCNTs, which underperform in transistors. Most synthesis routes yield mixtures of SWCNTs, typically 30% metallic and 70% semiconducting, necessitating the extraction of sc-SWCNTs from their metallic counterparts in high purity using scalable postsynthetic methods. Numerous routes to obtain high-purity sc-SWCNTs from raw soot have been developed, including density-gradient ultracentrifugation, chromatography, aqueous two-phase extraction, and selective DNA or polymer wrapping. By these methods (termed sorting or enrichment),99% sc-SWCNT content can be achieved. Currently, all of these approaches have drawbacks and limitations with respect to electronics applications, such as excessive dilution, expensive consumables, and high ionic impurity content. Excess amount of dispersant is a common challenge that hinders direct inclusion of sc-SWCNTs into electronic devices. At present, conjugated polymer extraction may represent the most practical route to sc-SWCNTs. By the use of polymers with a π-conjugated backbone, sc-SWCNTs with99.9% purity can be dispersed in organic solvents via a simple sonication and centrifugation process. With 1000 times less excipient and the flexibility to accommodate a broad range of solvents via diverse polymer constructs, inks are readily deployable in solution-based fabrication processes such as aerosol spray, inkjet, and gravure. Further gains in sc-SWCNT purity, among other attributes, are possible with a better understanding of the structure-property relationships that govern conjugated polymer extraction. This Account covers three interlinked topics in SWCNT electronics: metrology, enrichment, and SWCNT transistors fabricated via solution processes. First, we describe how spectroscopic techniques such as optical absorption, fluorescence, and Raman spectroscopy are applied for sc-SWCNT purity assessment. Stringent requirements for sc-SWCNTs in electronics are pushing the techniques to new levels while serving as an important driver toward the development of quantitative metrology. Next, we highlight recent progress in understanding the sc-SWCNT enrichment process using conjugated polymers, with special consideration given to the effect of doping on the mechanism. Finally, developments in sc-SWCNT-based electronics are described, with emphasis on the performance of transistors utilizing random networks of sc-SWCNTs as the semiconducting channel material. Challenges and advances associated with using polymer-based dielectrics in the unique context of sc-SWCNT transistors are presented. Such transistor packages have enabled the realization of fully printed transistors as well as transparent and even stretchable transistors as a result of the unique and excellent electrical and mechanical properties of sc-SWCNTs.

Cyanoethylated pullulan (CEP), a high-k solution processable polymer gate dielectric, is used to fabricate bottom gated single wall carbon nanotube (SWCNT) network thin film transistors (TFTs). Both aqueous and organic dispersions of highly semiconducting enriched SWCNTs are used as the channel material. Use of CEP as the dielectric enables fabrication of devices operating at low voltage (1 Hz) is found to significantly decrease the transconductance. This is shown to be related to a significant frequency dependence of the capacitance associated with a slow polarization response of the dielectric. Despite this limitation, CEP could be a useful dielectric in SWCNT TFTs for applications such as sensors and low frequency amplifiers.

Here, we present a metrological perspective on SWCNT optics, covering only the most essential photophysics, discussing sample properties and conditions that affect optical characterization, and the current metrological application of the most important optical characterization methods. We give a perspective on the continued development of nanotube metrology. Standards meetings, technical specifications, and other standard documents and protocols, as well as SWCNT reference materials are reviewed., Series: World Scientific Series on Carbon Nanoscience, Series: Handbook of Carbon Nano Materials

Photoluminescence excitation mapping used routinely to characterize semiconducting single-walled carbon nanotubes (sc-SWCNTs) is extended to provide time-dependent data. A hyperspectral method based on a supercontinuum light source and an imaging detector is demonstrated with excitation and emission wavelengths spanning 600–1000 and 1050–1650 nm, respectively, at time scales

Enrichment schemes providing high-purity semiconducting single-walled carbon nanotubes (sc-SWCNTs) will enable their implementation into high end and printed electronics. Conjugated polymer extraction (CPE) has been shown to be a very effective and scalable method to isolate sc-SWCNTs with purities >99.9%. However, this method is often plagued with variability, and the mechanism is not thoroughly understood. Herein, we probe the origins of selectivity in polyfluorene-assisted enrichment using poly(9,9-di-n-dodecylfluorene) (PFDD) and find that the affinity of the wrapping polymer to bind metallic (m-) and semiconducting SWCNTs is similar and may not contribute to the selectivity, but rather that oxygen-driven p-doping of the nanotubes and its dependence on the surface acidity may play a vital role for the selective dispersion of sc-SWCNT. The latter hypothesis is tested by titration experiments in which sodium hydroxide (NaOH) is used to neutralize the SWCNT surface, thus mitigating oxygen p-doping of SWC...

Author(s): Sun, J; Sapkota, A; Park, H; Wesley, P; Jung, Y; Maskey, BB; Kim, Y; Majima, Y; Ding, J; Ouyang, J; Guo, C; Lefebvre, J; Li, Z; Malenfant, PRL; Javey, A; Cho, G | Abstract: A limitless-length flexible active-matrix implies that virtually any surface can be rendered into an interactive medium when laminated with electrophoretic or organic light-emitting diode sheets. However, performance, cost, and size limitations of current fabrication technologies and semiconducting materials, typically utilized in thin film transistor (TFT) active matrices (TFT-AMs), have hindered progress, thus preventing the realization of fully printed TFT-AMs on a plastic roll. A new high-purity semiconducting single-walled carbon nanotube (s-SWCNT) ink is prepared by first isolating 99.9% pure s-SWCNTs via conjugated polymer extraction, and then utilizing a ligand-exchange method to formulate a novel hydrophilic gravure-compatible semiconducting ink. Based on the s-SWCNT ink, a fully additive manufacturing process using roll-to-roll (R2R) gravure printing enables the fabrication of a flexible TFT-AM, overcoming performance, cost, and size limitations. TFT-AMs with 10 to 40 PPI resolution where average mobility of 0.23 ± 0.12 cm2 V−1 s−1, average on–off ratio of 104.1, and threshold voltage variation of ±13% are attained. As a proof of concept, an inexpensive and flexible electrophoretic display is demonstrated by simply laminating an electrophoretic sheet onto the R2R gravure-printed s-SWCNT-based TFT-AM.

Spontaneously charged aerosol droplets, each containing a few single-walled carbon nanotubes wrapped in conjugated polymers were precipitated on a target substrate using electrostatic forces. Nanotube networks were assembled on a variety of dielectric surfaces including polymers with low surface energy: Good transistor performance was achieved in all cases. Under proper regime of electrostatic and flow fields, patterns were produced in a maskless fashion and feature sizes below 150 μm were demonstrated.

Representing the Holocaust raises fundamental questions regarding the almost impossible task of reproducing a specific ‘reality’ on-screen. Animation provides an environment that is both realistic and metaphoric and thus it enables the viewer to imagine the claustrophobic reality of life in the Warsaw Ghetto and access an emotional truth.

The trunk the traveller drags along is shown in a variety of powerful shots as he makes his way uphill. It conjures up two familiar myths: Sisyphus and Pandora’s box, which provide interesting clues regarding the symbolic significance of such a voyage.

The thermal oxidation of carbon nanotubes in air is investigated by in situ Raman spectroscopy. Etching rates are directly seen to be diameter, chirality, and type dependent. We directly track the evolution of bundled nanotube networks that undergo air etching from 300 to 600 °C. Some species are more robust than others. Changes to radial breathing mode (RBM) and G– peak structures suggest that metallic species etch away more rapidly, with smaller diameter semiconducting species etching more slowly and large diameter nanotubes, including semiconductors, etching last. The decay in integrated G and D band intensities is tracked and fit reasonably well with biexponential decay. The RBM evolution is better represented by a single exponential. All bands are fit to activation plots with RBMs showing significantly different rates.

Single-walled carbon nanotube (SWCNT) ensembles are characterized by their defect density and diameter distribution. Here, SWCNTs are grown using chemical vapor deposition with acetylene as the carbon source and cobalt as the catalyst and analyzed ex situ, without any modification or processing, using Raman spectroscopy. The defect density shows an activated temperature dependence (activation energy ∼0.8 eV or ∼80 kJ/mol) with fewer defects at high growth temperatures for a wide range of experimental parameters. This is consistent with a single activated mechanism, such as the catalytic healing of defects, possibly a single simple defect. Consistent with previous reports, we see that low growth temperatures produce smaller diameter SWCNTs than high growth temperatures. Elementary thermodynamic considerations of the strain energy in the lattice constrain the SWCNT diameter distribution and its temperature dependence and appear consistent with our observations. A “phase diagram” for SWCNT growth is constructed and suggests methods of controlling the diameter distribution. There is a trade-off here between small diameter SWCNTs and SWCNTs with low defect densities.

Individual air-suspended single-walled carbon nanotubes are imaged both spatially and spectrally in photoluminescence. At low excitation power, photoluminescence is bright and stable with high quantum efficiency; however, higher power initially causes a gradual red shift and then more severe changes. Blinking, the loss of quantum efficiency, and the appearance of new deep levels are all seen and can be explained by the introduction of defects. We propose that optical excitation induces molecular deposition onto the nanotube by optically induced van der Waals interactions, leading to physisorption and ultimately chemisorption which severely degrades the luminescence.

Carbon nanotube forests are arrays of roughly vertically aligned nanotubes. Under certain growth conditions, these forests can show a growth instability that gives rise to periodic ripples that are coherent over a forest-sized scale. Previously, we showed that the uniformity and synchronization of the ripples is sufficient for them to behave as diffraction gratings for visible light. Here, we identify the conditions that reproducibly promote the formation of these ripples. We investigate the formation mechanism via ex situ scanning electron microscopy and in situ optical imaging. While the rippling amplitude varies appreciably, the rippling wavelength varies very little and can be estimated from simple mechanical considerations. We provide evidence that the rippling is a consequence of cohesive interactions between nanotubes and the build up of strain, driven by a non-uniform growth rate. The origin of the non-uniform growth rate is explained.

Polarized light microscopy (PLM) is used to image individual single-walled carbon nanotubes (SWNTs) suspended in air across a slit opening. The imaging contrast relies on the strong optical anisotropy typical of SWNTs. We combine PLM with a tunable light source to enable hyperspectral excitation spectroscopy and nanotube chirality assignment. Comparison with fluorescence microscopy and spectroscopy confirms the assignment made with PLM. This represents a versatile new approach to imaging SWNTs and related structures. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

International audience; Several fractions of wheat fibres were isolated from starchy endosperm, aleurone layer and bran, and characterized for their hydration properties and arabinoxylans (AX) content. The influence of their addition, up to 10%, to standard flour was studied through mixing tests, and rheological tests at small and large deformations. The effect of insoluble AX on dough development was accounted for by their capacity to retain water, whatever their origin and percentage of addition. The addition of insoluble AX increased the viscoelastic plateau modulus. The addition of soluble and insoluble AX to the dough did not modify the overall dough flow behaviour in shear, characterized by a Newtonian plateau at low shear rates followed by shear-thinning behaviour at larger shear rates. This behaviour could be fitted by the Cross model. The addition of water soluble AX modified the Newtonian viscosity value. Conversely, the addition of insoluble ones increased dough consistency, probably through a filler-like effect in the dough matrix.

The dynamical evolution of nanotube chemical vapor deposition growth was investigated by in situ spectroscopy of three main Raman bands: G, D, and RBM. The evolution in diameter distribution is inferred from RBM and G bands, and the evolution in crystallinity is determined from D and G bands. A consistent sequence of the growth evolution is observed, with four discernible phases: incubation, acceleration, linear growth, and termination. The temperature dependence of each of these stages of growth is experimentally determined, and characteristic energy scales apparently associated with each phase are extracted. The growth becomes slower as the temperature increases, with activated, parasitic reactions suggested as a cause. We explore to what extent one diameter grows in comparison to another and thus gain some insight into how the nanotube population changes with time.

Due to their high surface area, monoatomic wall thickness, electronic structure (band gap, van Hove singularities) and properties (high mobility, ambipolar transport), single-walled carbon nanotubes (SWNTs) stand as a promising active material for chemical sensors. In a sensor context, they however suffer from lack of selectivity. For the same reasons that they are highly sensitive to analytes, they will be affected by their environment: interference from ambient gases (i.e. O2 / H2O redox couple) are to be expected [1,2], and vicinal charges and dipoles [3,4] will change the local electrostatics felt by the SWNTs. The dielectric environment being an integral part of the field-effect transistor (FET) stack, we sought to understand its effect on the transfer characteristics of devices with a carbon nanotube network as the active channel component. References [1] Aguirre, C. M. et al. The Role of the Oxygen/Water Redox Couple in Suppressing Electron Conduction in Field-Effect Transistors. Adv. Mater. 21, 3087–3091 (2009). [2] Lefebvre, J. et al. Hysteresis free carbon nanotube thin film transistors comprising hydrophobic dielectrics. Appl. Phys. Lett. 107, 243301 (2015). [3] Kobayashi, S. et al. Control of carrier density by self-assembled monolayers in organic field-effect transistors. Nat. Mater. 3, 317–322 (2004). [4] Lee, S.-H. et al. Effect of Polymer Gate Dielectrics on Charge Transport in Carbon Nanotube Network Transistors: Low-k Insulator for Favorable Active Interface. ACS Appl. Mater. Interfaces 8, 32421–32431 (2016).

Semiconducting single-walled carbon nanotubes (sc-SWCNTs) enriched by a conjugated polymer extraction process have been actively studied for various applications in both electronics and optoelectronics. Although the resulting tube samples usually have high sc-purity and concentration, SWCNT networks from such dispersions typically contain residual conjugated polymer that may degrade device performance and its removal remains a challenge while maintaining uniform, dense SWCNT thin film networks. In this study, a novel polymer–SWCNT combination based on an alternating bisfuran-s-tetrazine and benzo[1,2-b:4,5-b′]dithiophene copolymer abbreviated as PBDTFTz is proposed. This polymer decomposes at >250 °C or under UV irradiation. In situ transistor characterization under laser irradiation confirms the polymer decomposition. The study of the tube network in the transistor channel at various channel lengths reveals significantly reduced contact resistance attributed to removal of the wrapping PBDTFTz polymer. In ammonia sensing experiments, sc-SWCNT networks demonstrate rapid and reversible responses, while the unwrapped nanotube networks prove superior in terms of signal to noise ratio and a detection limit of 2.5 ppb is calculated, almost four times better than polymer wrapped nanotubes.

Single-walled carbon nanotubes (SWNTs) are commonly synthesized in bundles for which the luminescence is often quenched altogether. Here, we report on the simplest case of nanotube bundles: a single pair of individual air-suspended SWNTs. Using luminescence imaging spectroscopy, we find that emission and excitation spectra can be described within an energy transfer picture, with donor to acceptor transfer of excitation. The multiplicity of emission peaks in small bundles indicates that the transfer of luminescence is only partial at room temperature, with thermal occupation of the donor being significant. We attribute this signature to the unique band structure of SWNTs, with diameter and chirality dependent energy, recombination rate, and density of states.

Retardation test, step-shear rate experiments, low-amplitude and large-amplitude dynamic measurements have been combined to study the nonlinear and time-dependent viscosity of dough and shear-induced effects of flow on dough structure. Despite large quantitative differences in linear viscoelastic constants, doughs from different flours or with different water contents display the same type of flow behaviour. Shear-induced structural changes cause flow to shift from a high viscosity steady-state regime to a low viscosity one. The process, irreversible, is responsible for the time-dependent character of dough viscosity and seems to be controlled by the mechanical energy absorbed. Nevertheless, the two steady-state viscosities follow the same shear-thinning flow curve, fitted by a Cross equation with an exponent close to 1; the Newtonian plateau is approached at very low shear rate values. Viscosity data obtained on different doughs yield a unique flow master curve in reduced coordinates. Shear-induced structural changes cause also the linear viscoelastic plateau modulus of dough to decrease; this progressive weakening of the network structure is irreversible and seems governed by the accumulated strain. These characteristics of dough rheology are discussed with reference to the behaviour of concentrated suspensions.

Axe 2 Structuration sous contraintes des agropolymères et réactivité des poudres Contact: fax: +33 (4) 9961 3076. E-mail address: morel@supagro.inra.fr; International audience; The mechanism of gluten network development is still unclear and remains difficult to study since gluten network formation in bread dough is a rather quick process. In order to better characterize this dynamic event, we slowed down its kinetics by increasing the dough water content. During mixing, performed with a planetary mixer at variable mixing speeds and flour/water ratios, the torque was recorded. Common flours from wheat cultivars Orvantis, Caphorn and Isengrain, similar in composition and Farinograph parameters, were studied. At low flour/water ratios, mixing curves showed a lag phase preceding the increase of torque to the maximum dough resistance peak. Lag phase duration increased with dough water content, whereas increasing the mixing speed decreased time for optimal dough development. For the three flours studied, the time for optimal dough development was found to be related to the instantaneous power delivered to the dough during the lag phase and not to the specific mechanical energy required to get the maximum torque. Besides the effect of this common control parameter, flours exhibited wide variations in response to a given instantaneous power delivery, with dough development times varying by a factor of 6. Orvantis was always faster to develop than Caphorn or Isengrain. Optical microscopy observations of batters, using a protein stain, showed that gluten network development resulted from two successive phenomena. The first one involved the formation of microscopic gluten lumps, and the second one consisted of the development of gluten strands starting, at the end of the lag phase. The very different behaviours observed for the three flours are discussed in relation to the batter structure and to the colloidal properties of Gluten proteins

Dynamic measurements and retardation tests were combined to characterise the linear viscoelastic behaviour of wheat flour dough in the 10 −5 –10 2 rad/s frequency range. Analysis of the data provided the Newtonian steady-state viscosity, the steady-state compliance, the terminal relaxation time, the viscoelastic plateau compliance and a measure of the upper frequency limit of the viscoelastic plateau. The influence of dough water content and composition of high molecular weight glutenin subunits on dough viscoelasticity was studied. Both factors affected dough viscoelasticity in a similar and remarkable way. In particular, the same inverse relationship between steady-state viscosity and compliance, and the same power law relationship between steady-state and plateau compliances, was found to hold whether the variability was due to high molecular weight glutenin subunits or to dough water content.

SWCNT network morphology and TFT performance of polyfluorene wrapped sc-SWCNT on different substrates is reported. The polymer/tube weight ratio and concentration impacts network formation and device performance. Hydrophilic SiO2 surfaces show stronger adsorption compared to poly-l-lysine treated SiO2, which leads to more uniform and higher density networks. TFTs with mobility up to 38 cm2/Vs with

A novel purification process for the enrichment of sc-SWCNTs that combines selective conjugated polymer extraction (CPE) with selective adsorption using silica gel, termed hybrid-CPE (h-CPE), has been developed, providing a high purity sc-SWCNT material with a significant improvement in process efficiency and yield. Using the h-CPE protocol, a greater than 5 fold improvement in yield can be obtained compared to traditional CPE while obtaining sc-SWCNT with a purity99.9% as assessed by absorption spectroscopy and Raman mapping. Thin film transistor devices using the h-CPE derived sc-SWCNTs as the semiconductor possess mobility values ranging from 10-30 cm(2) V(-1) s(-1) and current ON/OFF ratio of 10(4)-10(5) for channel lengths between 2.5 and 20 μm.