Marion Castilla | Searcharxiv

arXiv2022

Colloidal Synthesis of Crystalline Aluminum Nanoparticles for UV Plasmonics

Numerous applications of nanotechnologies rely on the wide availability of high-quality crystalline nanoparticles (NPs). Although the chemical synthesis of noble metal nanoparticles (gold and silver) is well mastered, pushing the optical response of metallic nanoparticles towards the ultraviolet requires other materials, such as aluminum. Although a few demonstrations of chemical synthesis of Al nanoparticles have been reported so far, an elaboration path allowing for a wide range of NP size that is compatible with mass production has yet to be demonstrated. In this article, we report on the production of spherical, size-controlled crystalline Al NPs starting from commercial Al foils and without the use of a catalyst. The proposed method combines sonochemistry with solvochemistry and is fully up-scalable. The obtained NPs have a 10-100 nm crystalline Al core surrounded by a thin alumina shell, allowing long-term stability in ethanol. Well-defined plasmonic resonances in the UV and visible ranges are experimentally evidenced on single nanoparticles.

cond-mat.mtrl-sci↗

arXiv2021

Hybridization and Dehybridization of Plasmonic Modes

The plasmon resonances (modes) of a metal nanostructure can be defined as a dipole, a quadrupole, or high-order modes depending on the surface charge distribution induced by the incident field. In a non-symmetrical environment or clusters, the modes can hybridize and exhibit different behavior and properties. In this work, we study experimentally and numerically the substrate-induced hybridization of plasmonic modes of a silver nanocylinder. The applications of plasmonic nanoparticles such as refractive index sensing and enhanced spectroscopies often rely on the sustained mode spectral position and specific spatial near-field distribution. However, we show that the implementation of such plasmonic nanoparticles in a sensing system can result in a change of the modes nature, its hybridization or dehybridization. These changes are not clearly pronounced in the far-field spectra and then may result in unexpected modifications of the sensor behavior. We show that the hybridization between the dipolar and quadrupolar modes of the plasmonic nanoparticle on the substrate results from quadrupolar mode excitation due to the superposition of the reflected and incoming light and, then, depends on the reflection of the substrate. The existence of the hybridized modes strongly depends on the surrounding environment of nanoparticles, and after the deposition of the nanometric polymer layer on top of the nanoparticle the hybridized modes vanish and are replaced by uncoupled multipolar resonances.

physics.optics↗