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

From diagnosis of life-threatening diseases to detection of biological agents in warfare or terrorist attacks, biosensors are becoming a critical part of modern life. Many recent biosensors have incorporated carbon nanotubes as sensing elements, while a growing body of work has begun to do the same with the emergent nanomaterial graphene, which is effectively an unrolled nanotube. With this widespread use of carbon nanomaterials in biosensors, it is timely to assess how this trend is contributing to the science and applications of biosensors. This Review explores these issues by presenting the latest advances in electrochemical, electrical, and optical biosensors that use carbon nanotubes and graphene, and critically compares the performance of the two carbon allotropes in this application. Ultimately, carbon nanomaterials, although still to meet key challenges in fabrication and handling, have a bright future as biosensors.

Carbon Nanomaterials in Biosensors: Should You Use Nanotubes or Graphene?

Building an electronic device using individual molecules is one of the ultimate goals in nanotechnology. To achieve this it will be necessary to measure, control and understand electron transport through molecules attached to electrodes. Substantial progress has been made over the past decade and we present here an overview of some of the recent advances. Topics covered include molecular wires, two-terminal switches and diodes, three-terminal transistor-like devices and hybrid devices that use various different signals (light, magnetic fields, and chemical and mechanical signals) to control electron transport in molecules. We also discuss further issues, including molecule-electrode contacts, local heating- and current-induced instabilities, stochastic fluctuations and the development of characterization tools.

Electron transport in molecular junctions.

Nanostructuring electrodes with carbon nanotubes: A review on electrochemistry and applications for sensing

Stochastic on-off conductivity switching observed in phenylene-ethynylene oligomers has been explained in terms of changes in ring conformations, or electron localization, or both. We report the observation of stochastic on-off switching in the simplest of wired molecules: octanedithiol, decanedithiol, and dodecanedithiol bonded on an Au(111) surface. Stochastic switching was observed even when a top gold contact was pressed on by a conducting atomic force microscope tip at constant force. The rate of switching increased substantially at 60°C, a temperature at which these films are commonly annealed. Because such switching in alkanethiols is unlikely to be caused by internal molecular electronic changes and cannot be fully accounted for by breaking of the top contact, we argue that the cause is the well-known mobility of molecules tethered to gold via a thiol linkage.

https://science.sciencemag.org/content/sci/300/5624/1413.full.pdf

A Bond-Fluctuation Mechanism for Stochastic Switching in Wired Molecules

We describe a method of measuring the electrical properties of a molecule via conducting atomic force microscopy (AFM). A dithiolated molecule is chemically inserted into defect sites in an insulating self-assembled monolayer formed on an epitaxial Au substrate and the top thiol terminus of the molecule is reacted with a Au nanoparticle. A Au-coated AFM probe is used to contact the molecule through the nanoparticle, thus electrical data can be obtained. We report preliminary transport measurements of two test molecules. Our data shows qualitative agreement with previously published results for similar molecules deposited in a nanopore containing approximately a thousand molecules. This work indicates that the measured negative differential resistance is not an intermolecular phenomenon.

Electrical measurements of a dithiolated electronic molecule via conducting atomic force microscopy

In situ detection of cytochrome c adsorption with single walled carbon nanotube device

We are developing a 'toolbox' containing organic molecules, nanoparticles and carbon nanotubes (CNTs) that can be self-arranged into a very advanced information processing system. Before we can assemble these 'tools' in complex systems, it is imperative that we determine their physical, chemical and electrical properties. Here, we describe the development of three techniques to aid in evaluating the electrical properties of these 'tools'. Firstly, via a conducting atomic force microscope, we will examine a method of measuring the electrical properties of a single (few) dithiolated electronic molecule(s) inserted into an 'insulating' self-assembled monolayer (SAM). Secondly, to expedite the transport measurements of electronic molecules, we will present a hybrid assembly technique that consists of forming a SAM of the investigated molecule on pre-patterned electrodes and then bridging the electrodes with Au nanoparticles using an alternating electric field. Finally, to integrate single-wall carbon nanotubes into a circuit, we will outline a single optical lithographic step approach to pattern catalyst islands on top of metal electrodes. Then, reduced pressure chemical vapour deposition is performed on the patterned substrates to form CNTs bridging neighbouring electrodes and produce a circuit which is ready to test.

A molecular electronics toolbox

A probe (10,30,40) for forming images of surfaces (11) facilitates simultaneous formation of both thermal and atomic force microsocopy images. The probe (10,30,40) includes a heat sensing assembly (15) that has a heat sensing element (19,38,42). An electrically isolating and thermally conductive tip (22,48) projects from the heat sensing assembly. The probe (10) also has a reflective element (24) that is positioned between a first end of the heat sensing assembly (15) and the electrically isolating and thermally conductive tip (22).

Theresa J. Hopson

Papers

A Bond-Fluctuation Mechanism for Stochastic Switching in Wired Molecules

Electrical measurements of a dithiolated electronic molecule via conducting atomic force microscopy

In situ detection of cytochrome c adsorption with single walled carbon nanotube device

A molecular electronics toolbox

Probe for providing surface images