Gold bipyramids as a promising alternative to gold nanorods for analytical and biomedical applications

Gold nanobipyramids and nanorods of comparable dimensions were synthesized to evaluate and contrast their plasmonic, analytical, and photothermal performance. The bipyramids exhibited a markedly higher absorption spectral quality factor than the nanorods. For surface-enhanced Raman scattering comparison, both nanoparticle types were functionalized with thiolated nitrobenzene molecules, revealing an approximately fourfold higher enhancement factor for the bipyramids. Their analytical sensitivity was further assessed by monitoring the plasmon resonance wavelength shift in response to changes in the external refractive index, as well as variations in the thickness and refractive index of a nanoscale coating. In all cases, the bipyramids outperformed the nanorods. Additionally, both experimental and theoretical analyses confirmed the superior efficiency of bipyramids as photothermal agents for converting laser irradiation into heat. Effective photothermal inactivation of Escherichia coli was achieved under resonant laser excitation using either particle type. Given the recent advances in their synthesis, gold bipyramids emerge as highly promising alternatives to nanorods for a broad range of analytical and biomedical applications.