Carbon nanotubes (CNTs) exhibit a unique combination of excellent mechanical, electrical and electrochemical properties, which has stimulated increasing interest in the application of CNTs as components in (bio)sensors. This review highlights various design methodologies for CNT-based biosensors and their employment for the detection of a number of biomolecules. In addition, recent developments in the fields of CNT-based chemiresistors and chemically sensitive field-effect transistors are presented. After a critical discussion of the factors that currently limit the practical use of CNT-based biosensors, the review concludes with an outline of potential future applications for CNTs in biology and medicine.

Biosensors based on carbon nanotubes

Different types of carbon based electrodes have emerged over the last few years, significantly changing the scope and sensitivity of electroanalytical methods for the measurement of diverse targets from metal ions through gases to biological markers. This Highlight article shows how the use of carbon nanotube modified electrodes has led to a fundamental understanding of the location and nature of electron transfer processes on graphitic electrodes and to the realisation that edge plane pyrolytic graphite may represent, at present, an optimal electrode material of this type for electroanalysis.

New electrodes for old: from carbon nanotubes to edge plane pyrolytic graphite

Cyclic voltammetry is recorded of the oxidation of ferrocyanide on a glassy carbon electrode modified with multiple layers of single-walled carbon nanotubes. The current response is interpreted in terms of semi-infinite planar diffusion towards the macro-electrode surface and in terms of oxidation of the electroactive species trapped in pockets in between the nanotubes. A thin layer model is used to illustrate the effects of diffusion within a porous layer. It is found that a semi-infinite planar diffusion model alone is not appropriate for interpreting the kinetics of the electron transfer at this electrode surface. In particular, caution should be exercised in respect of comparing voltammetric peak-to-peak potential separations between naked electrodes and nanotube-modified electrodes for the inference of electrocatalysis via electron transfer via the nanotubes.

Cyclic voltammetry on electrode surfaces covered with porous layers: An analysis of electron transfer kinetics at single-walled carbon nanotube modified electrodes

We report the controlled synthesis of multiwalled carbon nanotube−quantum dot (CNT-QD) heterojunctions using the ethylene carbodiimide coupling procedure (EDC). Thiol-stabilized ZnS-capped CdSe quantum dots containing amine terminal groups (QD−NH2) were conjugated with acid-treated multiwalled carbon nanotubes (MWCNT) ranging from 400 nm to 4 μm in length. Scanning and transmission electron microscopy were used to characterize the conjugation process.

Covalent Coupling of Quantum Dots to Multiwalled Carbon Nanotubes for Electronic Device Applications

The discovery of carbon nanotubes has had a profound impact on many areas of science and technology, not least that of electroanalysis The properties and applications of carbon nanotubes themselves have been well reviewed in the literature and a number of reviews with an electrochemical emphasis have been published However, the modification of carbon nanotubes has recently been the focus of much research, primarily to improve their solubility in various solvents Yet modified carbon nanotube electrodes also allow the electrochemist to tailor the properties of the carbon nanotubes, or the electrode surface to impart desired properties such as enhanced sensing capabilities In this review we attempt to comprehensively cover the different chemical and electrochemical modification strategies and research carried out using modified carbon nanotubes for electroanalytical and bioanalytical applications Furthermore we also discuss the use of modified carbon nanotubes in electrocatalysis and biocatalysis from an analytical aspect, as well as seeking to dispel some of the myths surrounding the “electrocatalytic” properties of carbon nanotubes

Xian-Wen Wei

Papers

Electrocatalytic oxidation of nitric oxide at multi-walled carbon nanotubes modified electrode