Pulsed laser induced microbubble in gold nanorod colloid

The characterization of a pulsed laser induced microbubble (PLIMB) in gold nanorod (GNR) colloid was studied experimentally. The generation of PLIMB is due to the optical breakdown in water. Using an ultrasonic transducer and a probing He-Ne laser associated with a photodetector, the photoacoustic (PA) signals and the bubble formation of the multi-cycled oscillation of a single PLIMB were measured simultaneously. Both results are in agreement to show that the lifetime of PLIMB is reduced as the gold concentration increases. This phenomenon is attributed to the plasmonic light scattering (Faraday-Tyndall effect) in GNR colloid; the energy for optical breakdown is reduced at the focus due to laser-beam defocusing. The effect is particularly pronounced at the longitudinal surface plasmon resonance of GNRs. In addition, the divergence angle of 532-nm CW laser beam through gold nanoparticle (GNP) colloid was measured. Our results show that the divergence angle increases as the concentration of GNP increases.