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Highlights in Chemical Technology

Chemical technology news from across RSC Publishing.

Diamonds are for electron microscopy

28 September 2007

A team of UK scientists has developed a way of controlling the chemical vapour deposition of diamond to uniformly coat ultramicroelectrodes. These electrodes often have a diameter of less than 25 microns, ideally suited for scanning electrochemical microscopy (SECM).

The diamond ultramicroelectrode, from a variety of angles

SECM is a type of microscopy that images surfaces using a physical probe. By mechanically moving the probe across a surface, an accurate image of the surface can be mapped. The electrodes that are used as probes are known as ultramicroelectrodes (UMEs).

Diamond is an attractive material for electrodes because of its electrochemical characteristics and chemical inertness. However, up until now diamond UMEs could not be made using conventional chemical vapour deposition techniques. The team led by John Foord at the University of Oxford successfully modified the deposition process to produce diamond-coated ultramicroelectrodes. By combining efficient nucleation methods and an electrochemical bias during growth, the electrode can be coated with a uniform, polycrystalline diamond layer.

The team has been working in the area of diamond electrochemistry for a number of years and aims to produce diamond electrodes for probing biological media. Foord explained the challenge: 'Conventional microelectrodes fail to function in biological media because of adsorption of biological media, which foul the electrode,' he said. Diamond can be chemically functionalised to make it more stable than other electrodes under these conditions, he said, making it an ideal target material.

"Until now diamond ultramicroelectrodes could not be made using conventional chemical vapour deposition techniques"
Frank Marken from the University of Bath is an expert in novel electrode design and believes this work could have a wide impact. 'The availability of sharp, conducting diamond tools could be of wider significance... tools to "dissect" and image individual biological cells and their content could be envisaged as future developments.'

However, Foord believes that more work is needed before the full potential of these ultramicroelectodes is realised. A thin insulating coating for the body of the electrode is needed, which can be removed from the electrode tip without damaging it. The group is currently exploring the use of polymer coatings for this purpose.

May Copsey

Link to journal article

Hot filament chemical vapour deposition of diamond ultramicroelectrodes
Jingping Hu, John S. Foord and Katherine B. Holt, Phys. Chem. Chem. Phys., 2007, 9, 5469
DOI: 10.1039/b710241k

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