Plasmonic Response to Liquid–Solid Phase Transition in Individual Gallium Nanoparticles

Gallium is a phase-changing plasmonic material offering ultraviolet-to-near-infrared tunability, facile and scalable preparation, and good stability of nanoparticles. In this work, we explore the impact of the liquid-to-solid phase transition on their plasmonic properties at the single-particle level by analytical transmission electron microscopy. We observed a phase transition from liquid to β-gallium with a freezing temperature around -135 °C and a melting temperature around -20 °C. We have shown that the dipole mode of localized surface plasmon resonances can be tuned through their size from the ultraviolet to visible spectral region, while the differences in localized surface plasmon energies between liquid gallium at 25 °C and β-gallium nanoparticles at -177 °C are minor. Our results show that the performance of gallium nanoparticles is, in the case of temperature-dependent experiments, unaffected by the liquid-to-solid phase change of gallium and paves the way for suppressing the nonradiative recombination in surface-enhanced Raman spectroscopy at cryogenic temperature.