Super-Heating and Micro-Bubble Generation around Plasmonic Nanoparticles under cw Illumination

Under illumination, metal nanoparticles can turn into ideal nanosources of heat due to enhanced light absorption at the plasmonic resonance wavelength. In this article, we aim at providing a comprehensive description of the generation of microbubbles in a liquid occurring around plasmonic nanoparticles under continuous illumination. We focus on a common situation where the nanoparticles are located on a solid substrate and immersed in water. Experimentally, we evidenced a series of singular phenomena: (i) the bubble lifetime after heating can reach several minutes, (ii) the bubbles are not made of water steam but of air, and (iii) the local temperature required to trigger bubble generation is much larger than 100 degrees C: This last observation evidences that superheated liquid water, up to 220 degrees C, is easy to achieve in plasmonics, under ambient pressure conditions and even over arbitrary large areas. This could lead to new chemical synthesis approaches in solvothermal chemistry.