Recent Advances in Molecular Electronics Based on Carbon Nanotubes

Carbon nanotubes (CNTs) have exceptional physical properties that make them one of the most promising building blocks for future nanotechnologies. They may in particular play an important role in the development of innovative electronic devices in the fields of flexible electronics, ultra-high sensitivity sensors, high frequency electronics, opto-electronics, energy sources and nano-electromechanical systems (NEMS). Proofs of concept of several high performance devices already exist, usually at the single device level, but there remain many serious scientific issues to be solved before the viability of such routes can be evaluated. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. In our opinion, truly innovative use of these nano-objects will come from: i) the combination of some of their complementary physical properties, such as combining their electrical and mechanical properties, ii) the combination of their properties with additional benefits coming from other molecules grafted on the nanotubes, and iii) the use of chemically- or bio-directed self-assembly processes to allow the efficient combination of several devices into functional arrays or circuits. In this article, we outline the main issues concerning the development of carbon nanotubes based electronics applications and review our recent results in the field

Aligned carbon nanotube based ultrasonic microtransducers for durability monitoring in civil engineering

International audienceStructural health monitoring of porous materials such as concrete is becoming a major component in our resource-limited economy, as it conditions durable exploitation of existing facilities. Durability in porous materials depends on nanoscale features which need to be monitored in situ with nanometric resolution. To address this problem, we put forward an approach based on the development of a new nanosensor, namely a capacitive micrometric ultrasonic transducer whose vibrating membrane is made of aligned single-walled carbon nanotubes (SWNT). Such sensors are meant to be embedded in large numbers within a porous material in order to provide information on its durability by monitoring in situ neighboring individual micropores. In the present paper, we report on the feasibility of the key building block of the proposed sensor: we have fabricated well-aligned, ultra-thin, dense SWNT membranes that show above-nanometer amplitudes of vibration over a large range of frequencies spanning from 100 kHz to 5 MHz

Micro−transducteur ultrasonique capacitif à membrane de nanotubes de carbone : Perspectives pour le suivi immergé de la durabilité des matériaux cimentaires

Nous présentons des éléments de la conception, la réalisation et la caractérisation d'un micro−transducteur ultrasonique capacitif haute-fréquence dont la membrane vibrante est faite de nanotubes de carbone alignés. Le dispositif est conçu spécifiquement pour l'instrumentation immergée de la microporosité des matériaux cimentaires. La modélisation élasto−acoustique du dispositif valide préliminairement son intérêt applicatif pour la métrologie de la microporosité

High-sensitivity versus conventional troponin in the emergency department for the diagnosis of acute myocardial infarction

International audienceINTRODUCTION: Recently, newer assays for cardiac troponin (cTn) have been developed which are able to detect changes in concentration of the biomarker at or below the 99th percentile for a normal population. The objective of this study was to compare the diagnostic performance of a new high-sensitivity troponin T (HsTnT) assay to that of conventional cTnI for the diagnosis of acute myocardial infarction (AMI) according to pretest probability (PTP). METHODS: In consecutive patients who presented to our emergency departments with chest pain suggestive of AMI, levels of HsTnT were measured at presentation, blinded to the emergency physicians, who were asked to estimate the empirical PTP of AMI. The discharge diagnosis was adjudicated by two independent experts on the basis of all available data. RESULTS: A total of 317 patients were included, comprising 149 (47%) who were considered to have low PTP, 109 (34%) who were considered to have moderate PTP and 59 (19%) who were considered to have high PTP. AMI was confirmed in 45 patients (14%), 22 (9%) of whom were considered to have low to moderate PTP and 23 (39%) of whom were considered to have high PTP (P < 0.001). In the low to moderate PTP group, HsTnT levels ≥ 0.014 μg/L identified AMI with a higher sensitivity than cTnI (91%, 95% confidence interval (95% CI) 79 to 100, vs. 77% (95% CI 60 to 95); P = 0.001), but the negative predictive value was not different (99% (95% CI 98 to 100) vs. 98% (95% CI 96 to 100)). There was no difference in area under the receiver operating characteristic (ROC) curve between HsTnT and cTnI (0.93 (95% CI 0.90 to 0.98) vs. 0.94 (95% CI 0.88 to 0.97), respectively). CONCLUSIONS: In patients with low to moderate PTP of AMI, HsTnT is slightly more useful than cTnI. Our results confirm that the use of HsTnT has a higher sensitivity than conventional cTnI

Carbon nanotubes based ultrasonic transducer: realization process, morphological and mechanical properties

For instrumentation of microporosity in cementitous materials, carbon nanotubes based capacitive ultrasonic transducers (cMUT) are promising sensors. Their interest lies in the combination of high working frequencies (1 GHz) with small dimensions (1 µm²). In the proposed device, the cMUT membrane is made of aligned single-walled carbon nanotubes (SWNT) bridging a gap over a command electrode. We will describe the realization process of the vibrating membrane and its characterizations. First step of the device realization is the dispersion of SWNTs in N-methylpyrrolidone. Then, nanotubes are aligned by dielectrophoresis (DEP) between metallic electrodes onto a SiO2 substrate. A metallic layer is deposited over the electrodes edges to prevent nanotubes from slipping when suspended. The underlying SiO2 is then etched to release the membrane. Relevant features of the membrane are nanotubes alignment and density. Via SEM imaging, we have linked them with DEP operating parameters, in agreement with theoretical properties of DEP. To put a figure on membrane features, we are working on SEM image processing for nanotubes recognition. The method is based on advanced noise removal and contrast enhancement. First results of identification and measurement of intermeshed nanotubes on SEM pictures will be presented. We also mapped the Young's modulus of a suspended membrane using an AFM in contact mode, over surfaces of about 1 µm² surface. It opens the way for calculation of localized Young modulus, Poisson's ratio and thickness measurement of the membrane. We will check for correlations between mechanical data and quantitative properties of the deposition obtained from image processing. The optimization of membrane realization process and characterization techniques are presented, describing the present progress of our cMUT project. Next step will be actuation of the membrane to demonstrate vibrations at low frequency

Nanotubes de carbone comme matériau semi-conducteur pour l'électronique plastique : trier ou ne pas trier ?

National audienceLes nanotubes de carbone mono-parois sont obtenus par croissance d'un mélange de nanotubes semi-conducteurs et de nanotubes métalliques de diamètres similaires, mais différents par la chiralité de l'enroulement du feuillet de graphène qui constitue le tube. La synthèse séparée des deux types a été envisagée mais s'avère très difficile et à faible rendement. Cependant, les nanotubes semi-conducteurs sont d'excellents candidats pour l'électronique plastique : manipulable en solution comme des composés organiques, ils présentent d'excellentes mobilités et rapports courant ouvert/courant fermé proches de ceux des semi-conducteurs inorganiques.Pour éviter les court-circuit dus aux nanotubes métalliques présents dans le mélange de croissance, plusieurs méthodes de séparation ont été développées dans les 15 dernières années, dont deux ont permis la mise sur le marché de matériaux séparés. Nous verrons un aperçu de ces méthodes de séparation et de leurs usages pour l'électronique plastique, en comparaison d'autres matériaux imprimables. Notre laboratoire développe par ailleurs un traitement chimique sélectif permettant de supprimer la conductivité des nanotubes métalliques tout en conservant la qualité des nanotubes semi-conducteurs. Ce traitement simple, en phase aqueuse, évite la nécessité de séparer les deux types et fournit un matériau semi-conducteur imprimable à coût réduit

A highly selective non-radical diazo coupling provides low cost semi-conducting carbon nanotubes

International audienceSingle wall carbon nanotubes are synthesized as a mixture of semi-conducting (sc-CNT) and metallic (m-CNT). Both sc-CNT and m-CNT would find applications in electronics if separated, but the presence of the otherelectronic type in the mixture is very detrimental, in particular m-CNT shorting devices made of sc-CNTs. CNTsorting after electronic type has been widely studied, giving rise to very efficient separation methods in the past 10years. However the cost of separated sc-CNTs or m-CNTs remains too high for such low cost applications as plasticelectronics.We propose an alternative strategy where CNTs are treated with a covalent coupling selective for m-CNTs,and the mixture is used as a semi-conductive material without separation. Indeed, covalent coupling to m-CNTs cutstheir conductivity, while the sc-CNT quality is preserved thanks to the high selectivity of the diazoether reagent used[2], as a contrary to diazonium coupling [1].We will show how the unsorted semi-conducting CNT material can be produced in large quantity forprinting or spray processing. We will show what key role plays the quality of the CNT dispersion in water withsurfactant for reactivity, selectivity as well as ink stability. The origin of the high selectivity towards m-CNTcoupling will be discussed. Finally, we will show an example of implementation in transistors on plastic obtained byspray