The ultimate aim of any detection method is to achieve such a level of sensitivity that individual quanta of a measured entity can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity1, 2, 3, 4. The fundamental reason limiting the resolution of such sensors is fluctuations due to thermal motion of charges and defects5, which lead to intrinsic noise exceeding the sought-after signal from individual molecules, usually by many orders of magnitude. Here, we show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphene's surface. The adsorbed molecules change the local carrier concentration in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chemical detectors but also for other applications where local probes sensitive to external charge, magnetic field or mechanical strain are required.

/pdf/detection-of-individual-gas-molecules-adsorbed-on-graphene-2b3viubc4o.pdf

Detection of individual gas molecules adsorbed on graphene

The ultimate aspiration of any detection method is to achieve such a level of sensitivity that individual quanta of a measured value can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity. The fundamental reason limiting the resolution of such sensors is fluctuations due to thermal motion of charges and defects which lead to intrinsic noise exceeding the sought-after signal from individual molecules, usually by many orders of magnitude. Here we show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphenes surface. The adsorbed molecules change the local carrier concentration in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chemical detectors but also for other applications where local probes sensitive to external charge, magnetic field or mechanical strain are required.

Detection of Individual Gas Molecules Absorbed on Graphene

Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

/pdf/carbon-nanotubes-present-and-future-commercial-applications-1nhq3xy4hh.pdf

Carbon Nanotubes: Present and Future Commercial Applications

Department of Materials Science, University of Patras, 26504 Rio Patras, Greece, Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vass. Constantinou Avenue, 116 35 Athens, Greece, Institut de Biologie Moleculaire et Cellulaire, UPR9021 CNRS, Immunologie et Chimie Therapeutiques, 67084 Strasbourg, France, and Dipartimento di Scienze Farmaceutiche, Universita di Trieste, Piazzale Europa 1, 34127 Trieste, Italy

Chemistry of Carbon Nanotubes

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

We have used nanoscale field effect transistor devices with carbon nanotubes as the conducting channel to detect protein binding A PEI/PEG polymer coating layer has been employed to avoid nonspecific binding, with attachment of biotin to the layer for specific molecular recognition Biotin-streptavidin binding has been detected by changes in the device characteristic Nonspecific binding was observed in devices without the polymer coating, while no binding was found for polymer-coated but not biotinylated devices Streptavidin, in which the biotin-binding sites were blocked by reaction with excess biotin, produced essentially no change in device characteristic of the biotinylated polymer-coated devices

/pdf/electronic-detection-of-specific-protein-binding-using-h1mw113i0x.pdf

Electronic Detection of Specific Protein Binding Using Nanotube FET Devices

We report carbon nanotube network field-effect transistors (NTNFETs) that function as selective detectors of DNA immobilization and hybridization. NTNFETs with immobilized synthetic oligonucleotides have been shown to specifically recognize target DNA sequences, including H63D single-nucleotide polymorphism (SNP) discrimination in the HFE gene, responsible for hereditary hemochromatosis. The electronic responses of NTNFETs upon single-stranded DNA immobilization and subsequent DNA hybridization events were confirmed by using fluorescence-labeled oligonucleotides and then were further explored for label-free DNA detection at picomolar to micromolar concentrations. We have also observed a strong effect of DNA counterions on the electronic response, thus suggesting a charge-based mechanism of DNA detection using NTNFET devices. Implementation of label-free electronic detection assays using NTNFETs constitutes an important step toward low-cost, low-complexity, highly sensitive and accurate molecular diagnostics.

https://www.pnas.org/content/pnas/103/4/921.full.pdf

Label-free detection of DNA hybridization using carbon nanotube network field-effect transistors

Here we demonstrate design, fabrication, and testing of electronic sensor array based on single-walled carbon nanotubes (SWNTs). Multiple sensor elements consisting of isolated networks of SWNTs were integrated into Si chips by chemical vapor deposition (CVD) and photolithography processes. For chemical selectivity, SWNTs were decorated with metal nanoparticles. The differences in catalytic activity of 18 catalytic metals for detection of H2, CH4, CO, and H2S gases were observed. Furthermore, a sensor array was fabricated by site-selective electroplating of Pd, Pt, Rh, and Au metals on isolated SWNT networks located on a single chip. The resulting electronic sensor array, which was comprised of several functional SWNT network sensors, was exposed to a randomized series of toxic/combustible gases. Electronic responses of all sensor elements were recorded and the sensor array data was analyzed using pattern-recognition analysis tools. Applications of these small-size, low-power, electronic sensor arrays are...

Gas sensor array based on metal-decorated carbon nanotubes.

Nanotube network transistors have been transferred to polymer supports. The polymer-supported networks can be bent through at least 60° angles without changing their electronic properties. They ope...

Flexible Nanotube Electronics

the filter were measured using condensation particle counters (TSI Inc. model 3022A). Submicrometer particles entering the counters are grown into micrometer sized droplets by condensation of a supersatu-rated vapor of 1-butanol onto the particles, then counted by laser light scattering. The particle concentrations were averaged over ten measurements at each particle size. Filter experiments were repeated at least twice to ensure reproducibility. The pressure drop after filtration was also measured using previously described methods. [6] Raman spectra of CVD-grown MWNTs displayed higher relative intensities for the disorder mode (D-band) when compared to arc-Nearly all biologically significant reactions result in the production , or removal of carbon dioxide. Therefore, the sensing of CO 2 is important in a broad variety of applications. CO 2 sensors are currently used to monitor indoor air quality, and in capnographyÐthe measurement of CO 2 in respiration during medical procedures. For these applications, the current technologyÐinfrared spectroscopy, is limited by its power consumption, and size. Although a number of simplified CO 2 sensors have been proposed, [1] many significant problems, such as direct detection, low power consumption, and room temperature operation still remain unsolved. Field-effect transistors fabricated using carbon nanotubes (NTFETs) [2] have been recently explored as chemical [3,4] and biological [5] sensors. The response of the device characteristics to chemical analytes occurs via charge transfer between the NTFET and the analytes, as evidenced by experiments involving electron-donating (NH 3) and electron-withdrawing (NO 2) molecules. [2j,3a] Recent studies also demonstrate the effect of electron negativity of aromatic compounds on the NTFET electronic characteristics. [4] Whereas the NTFET devices are sensitive to the presence of strong charge donors and accep-tors, they are not sensitive to weak Lewis acids or bases such as H 2 , CO 2 , and CH 4. Specific sensitivity can be achieved by employing recognition layers that induce chemical reactions that modify the NTFET device characteristics. A catalytic-reaction based sensing of H 2 has been reported, [3c] together with a demonstration of a charge-transfer reaction-based sensing mechanism. Both mechanisms work at ambient temperature. In this communication, we report the design and fabrication of chemically functionalized NTFET devices for CO 2 sensing. [6] Figure 1a displays the sensor architecture: a NTFET transducer functionalized with a recognition layer specific for CO 2 gas. Although the chemical functionalization of carbon [**] We acknowledge the Nanomix technical staff for their assistance with device fabrication and measurements. (b) …

Jean-Christophe P. Gabriel

Papers

Electronic Detection of Specific Protein Binding Using Nanotube FET Devices

Label-free detection of DNA hybridization using carbon nanotube network field-effect transistors

Gas sensor array based on metal-decorated carbon nanotubes.

Flexible Nanotube Electronics

Nanoelectronic Carbon Dioxide Sensors