Plasmonic Sensing of Refractive Index and Density in Methanol-Ethanol Mixtures at High Pressure

Abstract

The localized surface plasmon resonance (LSPR) of gold nanospheres dispersed in methanol-ethanol 4:1 was measured as a function of pressure up to 60 GPa. The LSPR exhibits an intense red-shift with pressure in the range of 0-10 GPa, followed by a slower blue-shift at higher pressures. This is because an increase in the solvent refractive index with pressure leads to a red-shift of the LSPR peak wavelength while an increase in the electron density of the gold nanospheres with pressure leads to a blue-shift. Solvent solidification at 10 GPa and associated nonhydrostatic effects have a negligible influence on the LSPR shifts in the case of nanospheres. Here we show that both the LSPR shifts and..