Optical monitoring the dynamics of plasmonic nanobubbles

Laser generated bubbles surrounding plasmonic nanoparticles (known as plasmonic nanobubbles) are an attractive candidate approach for imaging and therapy, especially for cancer research. Nanobubbles are typically small in size (in microns), have a short lifetime (microseconds), and require complex instrumentation to characterize. Current approaches measure the bubble size using flash photography or an ultrafast camera and the bubble lifetime indirectly with a light scattering of a probe beam. Here, we demonstrate swept-source (1310+/-70 nm, 100 Khz scan rate) optical coherence tomography (OCT) as a new approach to monitoring plasmonic nanobubbles' dynamics. We recorded a one-dimensional (A-scan) analysis on a thin Au-nanoparticle-embedded gelatin layer and monitored the phase offset of the gelatin/air interface where nanobubbles were generated in response to a high energy single 10-ns 1064nm Nd: YAG laser pulse. We observed the gel/air interface movement reflecting the formation and collapse of nanobubbles with radius in the range of 200 – 600 nm and lifetime up to 100 microseconds corresponding to an incident laser fluence of 0.9 – 2.4J/cm2. We observed interface oscillations following nanobubble collapse. In conclusion, OCT may provide a simple technique to characterize both nanobubble's size and lifetime in response to pulsed laser irradiation of plasmonic nanoparticles.