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Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

Thermal Cycles and Electrohydrodynamic Instabilities in Plasmonic Nanofluids




Abstract

We measure an electrical response to the light-induced Rayleigh-Bernard-Marangoni convective instabilities in gold (Au)-polyvinylpyrrolidone (PVP) nanoparticles (NPs) suspended in isopropanol and water. The far-field fringe patterns of the laser propagation through the nanofluid provide signatures of its optical, thermal, and electrohydrodynamic response. We study the solvent-dependence of the self-synchronizing, light-induced thermal cycles, which coincide with nano-ampere current oscillations. The electrical currents are attributed to the presence of the Au-PVP NPs with a negative zeta potential, in correspondence with the accompanying thermal lens oscillations and a nanofluid thermoelectric effect. Our electrical current measurement characterize the Rayleigh-B\'{e}rnard-Marangoni convective instabilities. We show that the oscillations are convective instabilities dominated by strong Marangoni effect at the evaporating free surface. These electrical oscillations represent a new electrohydrodynamic instability driven by light, one among many that should be observed with plasmonic nanoparticles in liquids. The optical and electrical measurements allow us to estimate physical characteristics of the nanofluid, with some future challenges remaining for achieving a comprehensive readout of the thermal electrohydynamics.

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