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Xuehua Zhang1 2 3 Yuliang Wang3 4 Pengyu Lu3 Detlef Lohse3

1, University of Alberta, Edmonton, Alberta, Canada
2, RMIT University, Melbourne, Victoria, Australia
3, University of Twente, Enschede, , Netherlands
4, Beihang University, Beijing, , China

Microbubbles produced by plasmonic heating or chemical reactions play an important role in emerging and efficient plasmonic-enhanced processes for catalytic conversion, solar energy harvesting, biomedical imaging, and cancer therapy. In this work, the growth dynamics of nucleating bubbles from plamonic heating are studied to determine the exact origin of the occurrence and growth of these bubbles. The microbubbles were measured in air-equilibrated water (AEW) and degassed water (DGW) with fast imaging. Our experimental data reveals that the growth dynamics can be divided into two regimes: an initial bubble nucleation phase and subsequently a bubble growth phase. The explosive growth in regime I is identical for AEW and DGW due to the vaporization of water. However, the slower growth in regime II is distinctly different, which is attributed to the uptake of dissolved gas expelled from the water around the hot nanoparticle. We also experimentally and theoretically examine the growth and detachment dynamics of oxygen bubbles from hydrogen peroxide decomposition catalyzed by gold. We measured the bubble radius R(t) as a function of time by confocal microscopy. The results show that the dynamical evolution of bubbles is influenced by comprehensive effects combining chemical catalysis and physical mass transfer. The size of the bubbles at the moment of detachment is determined by the balance between buoyancy and surface tension and by the detailed geometry at the bubble’s contact line.

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