Abstract
When dissolved in water, a fluorescent solute absorbs the light of single-bubble sonoluminescence (SBSL), and emits light in longer wavelength region. This phenomenon is called single-bubble sonophotoluminescence (SBSPL). We measured SPSPL spectra for 1-pyrenebutyric acid (PBA), a kind of surfactant. Its molecules were expected to come closer to a bubble, absorbing the light of SL directly. However, for low concentrations of PBA, only insignificant changes were observed in the spectra in comparison with another fluorescent solute, fluorescein, which was not surface active. For high concentrations, a bubble became less stable, and SBSL did not occur for concentrations higher than 0.4mM, at which the surface activity began to play a significant role.
