Surface-enhanced photoacoustic wave generation from light absorbers located in the gap of high-refractive-index dielectric nanoparticles

Abstract

Plasmonic nanoparticles, such as Au nanoparticles, have been used as effective exogeneous contrast agents in photoacoustic imaging. However, using these particles to enhance photoacoustic wave generation from other light absorbers is difficult because the signal is overwhelmed by the signal from plasmonic nanoparticles themselves. In this study, we realized the surface-enhanced photoacoustic effect by using high-refractive-index dielectric nanoparticles in their ultralow light absorption Ohmic-loss wavelength band. We performed finite element method simulation on a model with gallium phosphide nanorod dimmer and light absorbers in the dimmer gap. The Au nanowire, carbon nanotube, and nanotube filled with melanin molecules were sequentially considered as the light absorber. It is found that a photoacoustic wave surface enhancement factor of approximately 10 was achieved and the enhanced photoacoustic wave ensures the photoacoustic spectral signature of the light absorber. The potential of optimization for boosting enhancement factors was further analyzed. These results can provide considerable insight into molecular photoacoustic sensing and imaging.