Ultramicroelectrodes (UMEs)- electrodes with a diameter less than 25 micrometres - find important uses in electrochemistry in areas such as the probing of biological tissue, or scanning electrochemical surface imaging. Chemical vapour deposited (CVD) diamond has attracted considerable interest as a macroscopic electrode material in recent years because of some attractive electrochemical characteristics. In this work, we demonstrate how specific film nucleation treatments and the use of an electrical bias can be used to modify the usual CVD diamond growth process, to produce UMEs which are optimised for electrochemistry.

What has motivated you to conduct this work?

We have studied diamond electrochemistry for a number of years, and wanted to produce diamond UMEs for use in scanning electrochemical microscopy (SECM), for imaging in biological media where conventional microelectrodes fail to function, because of surface adsorption of biological species, which foul the electrode. We found that successful diamond UMEs were not produced in our normal CVD growth process, and therefore began to explore changes in the growth conditions to overcome the problems we were encountering.

Where do you see this work developing in the future?

Our future work will be immediately concerned with the application of the diamond UMEs for SECM imaging in biological media. One of the attractive features of diamond is that it can be chemically functionalised in a way which is much more stable than for other electrodes. This offers an attractive route to the formation of UMEs which show a stable and highly selective electrochemical response. Some novel applications in the area of electrochemical luminescence also exist.

Are there any particular challenges facing future research in this area?

To fully realise the capabilities of these ultramicroelectrodes, thin insulating conformal coatings are required for the body of the electrode, which can be removed from the electrode tip in a geometrically well-defined way, without damaging it. We are beginning to explore the use of electrophoretically-deposited polymer coatings, in conjunction with focussed ion beam etching, to achieve this.