Foreword

When I think back to my first excursions into the world of ultrasound and its effects on chemical reactions it takes me back to 1975 when I obtained my first permanent academic post as an organic chemist at an institution that was then called Lanchester Polytechnic but later became Coventry University. The department I joined was Chemistry and Metallurgy, reflecting the applied nature of science courses at that time. One day I was walking through a metallurgy laboratory and saw an ultrasonic bath being used to clean metal samples. The process intrigued me for I could see that the ultrasonic bath was producing a large amount of energy as evidenced by the disturbance of the water with which it was filled. It occurred to me that this was perhaps a form of energy which might be employed to influence chemical reactivity using as an example a simple solvolysis reaction. However, the initial results were puzzling but I was sharing an office with a physical chemist, the late Phil Lorimer, but neither of us had heard of using ultrasound as a source of energy to promote chemical reactivity. Together we pursued this new subject and met many problems in convincing the UK science fraternity that we were ‘on to something big’. We produced our first paper in 1980 as a Chemical Communication, in which we reported a small (twofold) enhancement in the hydrolysis rate of 2-chloro-2-methylpropane. By 1986 the idea of using ultrasound to influence reactions had greatly expanded worldwide and we were involved in organising the first ever international conference on sonochemistry at Warwick University.

So where does electrochemistry fit into the development of sonochemistry? Phil Lorimer was originally an electrochemist and so had an interest in all things that might influence electrochemical processes. Together with another colleague, David Walton, we began to apply ultrasound to electrochemistry in the late 1980s and discovered that it could, for example, modify the electrochemical oxidation mechanism of cyclohexanecarboxylate. In 1990 we published a review using the term ‘Sonoelectrochemistry’ for the first time in a peer-reviewed journal. This review forced us to look at the literature surrounding the uses of ultrasound in electrochemistry and brought to light a number of research publications that had not previously been drawn together. Other sources have been unearthed since then, including the pioneering work of Young and Kersten in 1936 on the effects of ultrasonic radiation on electrodeposits. This was perhaps the first observation of improvements in hardness and brightness induced by ultrasound. Walker reinvestigated and advanced the work in the 1970s and in 1993 wrote a comprehensive review of his and other work entitled ‘Ultrasonic Agitation in Metal Finishing’. It is surprising to me that the very early work on sonoelectrochemistry has not been cited extensively. This is the case with the 1953 paper of Yeager and Hovorka entitled ‘Ultrasonic Waves and Electrochemistry’. It provided a survey of the electrochemical applications of ultrasonic waves that were discussed in terms of (i) the effects of ultrasonic waves on electrode processes, (ii) electrokinetic phenomena involving ultrasonic waves, and (iii) the use of ultrasonic waves as a tool in the study of the structure of electrolytic solutions.

Our own work in sonoelectrochemistry progressed at a pace and in 1995 we took on one of our own young and bright chemistry graduates to study for a PhD. He obtained his doctorate three years later with a thesis entitled ‘The Effect of Ultrasound upon Electrochemical Processes’ and his name was Bruno G. Pollet – the editor of this book. Bruno became more and more involved in the work on sonoelectrochemistry and looked at a range of topics, including the effect of ultrasonic frequency and power upon electrochemical systems, from the theory and modelling to ‘real’ industrial applications.

The group of authors that Bruno has assembled for this book have been able to cover many of the main areas of sonoelectrochemistry with contributions on fundamentals, analysis, organic synthesis, nanoparticles, polymerisation and much more. I recommend this book to you as a compendium of current thoughts and approaches to sonoelectrochemistry written by experts in the field.