The non-linear evolution of radiative properties of plasmonic nanofluid during light-induced vaporization process

Abstract

The light-induced vaporization process of plasmonic nanofluid plays an essential role in solar energy harvesting. Under light illumination, metallic nanoparticles can be converted into ideal thermal sources at nanoscale and generate plasmonic nanobubbles (PNBs) at the localized surface plasmon resonance (LSPR) wavelength, Therefore, the radiative properties of nanofluid closely correlate with the evolution of PNB nucleation, growth, fusion, and dissipation. A model based on finite element modeling is developed to investigate the evolution of radiative properties. The effect of gold nanoparticle (AuNP) size, PNB size, and AuNP aggregation morphology on the extinction cross section, albedo, and LSPR peak wavelength of particle-bubble complexes (P-B complexes) during the evolution of PNB is determined. The results indicate that with the vaporization process of nanofluid, the evolution of PNBs makes the radiation properties exhibit an obvious non-linear evolution pattern. Specifically, the generation of PNB shifts the LSPR peak wavelength towards blue, while the aggregation of AuNPs shifts it towards red. In the presence of PNB, the variation of the LSPR peak wavelength depends on the competition between the blue-shifting effect of PNB growth and the red-shifting effect of AuNP aggregation. After PNB dissipation, the aggregation of AuNPs raises the aggregates’ albedo. An albedo lower than 0.5 indicates a strong absorption of incident light energy. The increase in AuNP size, PNB size, and the aggregation of AuNPs all contribute to the increase in the peak extinction cross section. When PNB is present, whether the albedo of P-B complexes exceeds 0.5 depends on the relative magnitude of the extinction cross section of AuNP aggregates and PNB. The increase in the number of AuNPs aggregation layers causes the blue-shifted LSPR peak wavelength of AuNP aggregates, the decreased peak extinction cross section, the increased LSPR peak width, and the potential for multiple extinction peaks.