Characterisation of cavitation using electrochemical, acoustic and luminescent techniques (GR/M24615/01)

Characterisation of cavitation using electrochemical, acoustic and luminescent techniques (GR/M24615/01) T. G. Leighton and P. R. Birkin 1. Background There is an international need to understand the influence of cavitation on chemical and physical processes. While sonochemistry offers a variety of beneficial and appealing characteristics many limitations are apparent from the available literature. This is due in part to the diverse nature of sonochemistry, relying on aspects of chemistry, electrochemistry and acoustics. In general the understanding of the acoustic environment of a sonochemical cell is complex and relies on the characterisation of the transducer/cell/cavitation interaction that can be generated within the system as a whole. This fundamental problem often results in poor reproducibility between experiments and laboratories even though the same chemical environment and system is being employed (assuming no differences in the chemistry occur). In this context the proposed project set out to investigate cavitation using electrochemical sensors to characterise the chemical effects, while also employing luminescent and imaging technology to investigate the nature of the process termed ‘sonoluminescence’. In order to achieve these goals, controlled and characterised acoustic cells with the ability to generate cavitation were employed. Within these a further series of experiments was proposed to investigate the chemical and physical effects of cavitation. This involved the study of multi bubble and single bubble systems, each of which is known to have differing characteristics. While the single bubble sonoluminescent systems (SBSL) may initially be regarded as ‘simpler’ with the possibility to investigate a single event at one time, the difference in the observations reported in the literature between MBSL and SBSL have clouded the issues further. The project was successful in producing and characterising a set of sonochemical cells, which were then investigated using electrochemical, luminescent and imaging technology. Further to this, a link between sonoluminescence and sonochemical activity was verified, a new series of experimental procedures for the electrochemical detection of radical reactions was developed and the first electrochemical evidence for radicals produced by SBSL was found. While some results have yet to be published, the authors (TGL & PRB) have produced a series of high quality publications outlining the major results of the project (including 14 peer reviewed papers in the process of or published, with more in preparation in high quality journals). This success has led to 3 further EPSRC grants including non-academic sponsors all of which rely on well-characterised experimental procedures. In addition to these achievements the grant supported a PhD student directly plus (at no extra cost to the grant) an additional PhD student and 2 undergraduate final year projects.