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

Although graphite is known as one of the most chemically inert materials, we have found that graphene, a single atomic plane of graphite, can react with atomic hydrogen, which transforms this highly conductive zero-overlap semimetal into an insulator. Transmission electron microscopy reveals that the obtained graphene derivative (graphane) is crystalline and retains the hexagonal lattice, but its period becomes markedly shorter than that of graphene. The reaction with hydrogen is reversible, so that the original metallic state, the lattice spacing, and even the quantum Hall effect can be restored by annealing. Our work illustrates the concept of graphene as a robust atomic-scale scaffold on the basis of which new two-dimensional crystals with designed electronic and other properties can be created by attaching other atoms and molecules.

/pdf/control-of-graphene-s-properties-by-reversible-hydrogenation-2h7j2618ra.pdf

Control of graphene's properties by reversible hydrogenation: Evidence for graphane

This review addresses recent advances in carbon-nanotubes (CNT) based electrochemical biosensors. The unique chemical and physical properties of CNT have paved the way to new and improved sensing devices, in general, and electrochemical biosensors, in particular. CNT-based electrochemical transducers offer substantial improvements in the performance of amperometric enzyme electrodes, immunosensors and nucleic-acid sensing devices. The greatly enhanced electrochemical reactivity of hydrogen peroxide and NADH at CNT-modified electrodes makes these nanomaterials extremely attractive for numerous oxidase- and dehydrogenase-based amperometric biosensors. Aligned CNT “forests” can act as molecular wires to allow efficient electron transfer between the underlying electrode and the redox centers of enzymes. Bioaffinity devices utilizing enzyme tags can greatly benefit from the enhanced response of the biocatalytic-reaction product at the CNT transducer and from CNT amplification platforms carrying multiple tags. Common designs of CNT-based biosensors are discussed, along with practical examples of such devices. The successful realization of CNT-based biosensors requires proper control of their chemical and physical properties, as well as their functionalization and surface immobilization.

/pdf/carbon-nanotube-based-electrochemical-biosensors-a-review-372j6kup7u.pdf

Carbon‐Nanotube Based Electrochemical Biosensors: A Review

Electrical stimulation of nerve tissue and recording of neural electrical activity are the basis of emerging prostheses and treatments for spinal cord injury, stroke, sensory deficits, and neurological disorders. An understanding of the electrochemical mechanisms underlying the behavior of neural stimulation and recording electrodes is important for the development of chronically implanted devices, particularly those employing large numbers of microelectrodes. For stimulation, materials that support charge injection by capacitive and faradaic mechanisms are available. These include titanium nitride, platinum, and iridium oxide, each with certain advantages and limitations. The use of charge-balanced waveforms and maximum electrochemical potential excursions as criteria for reversible charge injection with these electrode materials are described and critiqued. Techniques for characterizing electrochemical properties relevant to stimulation and recording are described with examples of differences in the in vitro and in vivo response of electrodes.

https://www.annualreviews.org/doi/pdf/10.1146/annurev.bioeng.10.061807.160518

Neural stimulation and recording electrodes.

Natural and biomimetic artificial surfaces for superhydrophobicity, self-cleaning, low adhesion, and drag reduction

Multilayered metal catalysts for controlling the density of single-walled carbon nanotube growth

Vertically aligned multiwalled carbon nanotube (MWCNT) arrays can mimic the hairs on a gecko’s foot and act as a dry adhesive We demonstrate the van der Waals interactions originated dry adhesion between MWCNT array surfaces and various target surfaces over millimeter-sized contact areas The adhesive strengths were measured over 10N∕cm2 in the normal direction and about 8N∕cm2 in the shear direction with glass surface The adhesion strength over repeated cycles is limited by the relatively poor adhesion of MWCNTs to their growth substrate, which was improved significantly by adding molybdenum to the catalyst underlayer We also measured the interfacial work of adhesion as a fundamental adhesion property at the interface Our measured values of a few tens of mJ∕m2, which falls in the range of typical van der Waals interactions energies, provide a direct proof of the van der Waals dry adhesion mechanism Furthermore, in contrast to other dry adhesives, we show that MWCNT adhesives are electrically and the

Interfacial energy and strength of multiwalled-carbon-nanotube-based dry adhesive

A gate-insulated vacuum channel transistor was fabricated using standard silicon semiconductor processing. Advantages of the vacuum tube and transistor are combined here by nanofabrication. A photoresist ashing technique enabled the nanogap separation of the emitter and the collector, thus allowing operation at less than 10 V. A cut-off frequency fT of 0.46 THz has been obtained. The nanoscale vacuum tubes can provide high frequency/power output while satisfying the metrics of lightness, cost, lifetime, and stability at harsh conditions, and the operation voltage can be decreased comparable to the modern semiconductor devices.

Vacuum nanoelectronics: Back to the future?—Gate insulated nanoscale vacuum channel transistor

We report the detection of DNA PCR amplicons using an ultrasensitive label-free electronic technique based on multiwalled carbon nanotube (MWNT) nanoelectrode arrays embedded in an SiO(2) matrix. Specific PCR amplicons are reliably detected using electrochemical (EC) methods through allele-specific oligonucleotide hybridization. The inherent guanine bases in the DNA amplicon target of [Formula: see text] bases serve as signal moieties with the aid of Ru(bpy)(3)(2+) mediators, providing an amplified anodic current associated with the oxidation of guanine groups at the nanoelectrode surface. The reduced size and density of the nanoelectrode array provided by MWNTs dramatically improves the sensitivity of EC detection. In addition, the abundant guanine bases in target DNA produce a large signal. Less than [Formula: see text] target amplicons can be detected on a microspot, approaching the sensitivity limit of conventional laser-based fluorescence techniques. This method also eliminates the labelling requirement and makes the measurements much simpler. This platform can be employed for developing highly automated electronic chips with multiplex nanoelectrode arrays for quick DNA analysis.

Ultrasensitive label-free DNA analysis using an electronic chip based on carbon nanotube nanoelectrode arrays.

We demonstrate integration of carbon nanotubes into large scale vertically aligned electrode arrays, by filling the as-grown samples with conformal SiO2 using chemical vapor deposition. Subsequent mechanical polishing yields a flat surface with only the very ends of the nanotube array exposed. The electronic properties of individual carbon nanotubes in the array are measured using current-sensing atomic force microscopy. These vertical nanotube arrays are suitable for fabricating various electronic devices and sensors.

/pdf/electronic-properties-of-multiwalled-carbon-nanotubes-in-an-17dcif4gqm.pdf

M. Meyyappan

Papers

Multilayered metal catalysts for controlling the density of single-walled carbon nanotube growth

Interfacial energy and strength of multiwalled-carbon-nanotube-based dry adhesive

Vacuum nanoelectronics: Back to the future?—Gate insulated nanoscale vacuum channel transistor

Ultrasensitive label-free DNA analysis using an electronic chip based on carbon nanotube nanoelectrode arrays.

Electronic properties of multiwalled carbon nanotubes in an embedded vertical array