The Effect of Spike Geometry on the Linear and Nonlinear Plasmonic Properties of Gold Nanourchins

Domantas Peckus; Fatima Albatoul Kasabji; Maziar Moussavi; Loic Vidal; Hana Boubaker; Asta Tamuleviciene; Arnaud Spangenberg; Tomas Tamulevicius; Joel Henzie; Karine Mougin; Sigitas Tamulevicius

arXiv · 2507.03161

The Effect of Spike Geometry on the Linear and Nonlinear Plasmonic Properties of Gold Nanourchins

Domantas Peckus·Fatima Albatoul Kasabji·Maziar Moussavi·Loic Vidal·Hana Boubaker·Asta Tamuleviciene·Arnaud Spangenberg·Tomas Tamulevicius·Joel Henzie·Karine Mougin·Sigitas Tamulevicius

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Abstract

Wet-chemistry synthesized Gold nanourchins (Au NUs), characterized by spiky morphologies with spherical cores, exhibit complex and geometry-dependent plasmonic properties distinct from those of symmetrical nanostructures. While plasmon hybridization and mode coupling in branched nanostructures have been broadly studied, the specific optical behavior of Au NUs-particularly regarding spike length distribution and ultrafast dynamics-remains underexplored. This study investigates the steady-state and transient absorption spectra of Au NUs with 50-80 nm cores and 5-20 nm spikes, revealing multiple resonance bands. Transient absorption spectroscopy at various excitation wavelengths confirmed the presence of distinct resonances. Electromagnetic simulations based on TEM tomography-inspired models identified two key extinction bands: a green-wavelength dark mode resonance and a red-nIR spike-induced resonance attributed to the lightning rod effect. Simulations further showed that short, uniformly distributed spikes (aspect ratio <= 1) weakly excite dark resonances, while longer spikes (aspect ratio > 1) induce hybridized longitudinal resonances and significant redshifts. Broad spike length distributions result in multiple coexisting resonances, aligning with experimental extinction spectra. A preliminary surface-enhanced Raman scattering study using 2-naphthalene thiol confirmed stronger enhancement for long-spiked Au NUs under 785 nm excitation, validating the field enhancement potential of the identified resonances.

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Domantas Peckus, Fatima Albatoul Kasabji, Maziar Moussavi, Loic Vidal, Hana Boubaker, Asta Tamuleviciene, Arnaud Spangenberg, Tomas Tamulevicius, Joel Henzie, Karine Mougin, Sigitas Tamulevicius. 2025-07-03. The Effect of Spike Geometry on the Linear and Nonlinear Plasmonic Properties of Gold Nanourchins. https://arxiv.org/abs/2507.03161

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