M. Ashokkumar et al., The effect of pH on multibubble sonoluminescence from aqueous solutions containing simple organic weak acids and bases, J AM CHEM S, 121(32), 1999, pp. 7355-7359
The sonoluminescence (SL) intensity from aqueous solutions: containing eith
er all;yl acids or alkylamines is shown to be dependent on both the hydroca
rbon chain length of the solute and the pH of the solution. Alkylamines que
nch the SL only at pH values above about 9 whereas alkyl acids quench only
below about pH 7. In the pH ranges where SL quenching occurs, the longer th
e alkyl chain length the greater the effect. The results have been interpre
ted in terms of the neutral forms of the solutes adsorbing at the bubble/so
lution interface and then evaporating into the bubble core during its growt
h and compression oscillations, leading to the quenching of the SL. Possibl
e processes that may be responsible for the quenching are discussed.