Sonoluminescence quenching and cavitation bubble temperature measurements in an ionic liquid

A comparison between the temperatures within imploding acoustic cavitation bubbles and the extent of sonoluminescence (SL) quenching by C1–C5 aliphatic alcohols in 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4], a well known imidazolium based room temperature ionic liquid (RTIL)), has been made at an ultrasound frequency of 213 kHz. The temperatures obtained ranged from 3500 ± 200 K, in neat [EMIM][EtSO4], to about 3200 ± 200 K in RTIL-alcohol containing solutions. It was also found that the SL intensity decreased with increasing concentration (up to 1 M) of the alcohols to a greater extent compared with the relative changes to the bubble temperatures. Both the extent of the reduction in the bubble temperatures and the SL quenching were much smaller than those obtained in comparable aqueous solutions containing aliphatic alcohols. Possible reasons for the differences in the observed trends between water/alcohol and [EMIM][EtSO4]/alcohol systems under sonication at 213 kHz are discussed.