Bismuth nanoparticles are being investigated due to their reported photothermal and photocatalytic properties. In this study, we synthesized spherical bismuth nanoparticles (50-600 nm) and investigated their structural and optical properties at the single-particle level using analytical transmission electron microscopy. Our experimental results, supported by numerical simulations, demonstrate that bismuth nanoparticles support localized surface plasmon resonances, which can be tuned from the near-infrared to the near-ultraviolet spectral region by changing the nanoparticle size. Furthermore, plasmonic resonances demonstrate stability across the entire spectral bandwidth, enhancing the attractiveness of bismuth nanoparticles for applications over a wide spectral range. Bismuth's lower cost, biocompatibility, and oxidation resistance make bismuth nanoparticles a suitable candidate for utilization, particularly in large-scale and even industrial plasmonic applications.

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• Journal Article MeSH

Bismuth is a particularly promising alternative plasmonic metal because of its theoretically predicted wide spectral bandwidth. In this study, we experimentally demonstrate the correlation between the shape and size of individual bismuth plasmonic antennas and their optical properties. To this end, we employ a combination of scanning transmission electron microscopy and electron energy loss spectroscopy. Bar-shaped and bowtie bismuth plasmonic antennas of various sizes were fabricated by focused ion beam lithography of a polycrystalline bismuth thin film. Our experimental findings demonstrate that these antennas support localized surface plasmon resonances and their dipole modes can be tuned through their size from the near-infrared to the entire visible spectral region. Furthermore, our findings demonstrate that bismuth exhibits a plasmon dispersion relation that is nearly identical to that of gold while maintaining its plasmonic performance even at higher plasmon energies, thus rendering it a promising low-cost alternative to gold.

• Keywords
• bismuth, electron energy loss spectroscopy, localized surface plasmons, nanophotonics, plasmonic antennas,
• Publication type
• Journal Article MeSH

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.

• Publication type
• Journal Article MeSH