Photosensitization of nonlinear scattering and photoacoustic emission from single-walled carbon nanotubes

Enhancement of laser-induced nonlinear scattering has been observed from an aqueous suspension of single-walled carbon nanotubes (SWCNTs) doped with near-infrared dye chromophores. The underlying mechanism involves cavitation triggered by optical heating and bubble pulsation, which are further enhanced by the dye adsorbed on SWCNT surfaces, resulting in the scattering enhancement and a modification of the accompanying photoacoustic waveform. These photosensitizing effects suggest potential feasibility of dye-doped nanotubes as optically switchable nanoemitters of ultrasound for biomedical applications such as ultrasonic therapy and imaging.