Plasmon Resonances in Nanohemisphere Monolayers

Abstract

Plasmonic devices, consisting of nanoparticle monolayers, are conveniently fabricated by deposition techniques, wherein thermodynamics often favor the particle shape to be close to hemispherical. The present work investigates plasmon modes in Ag nanohemispheres (NHSs) using s-and p-polarized incident radiation at varying angles. The Ag NHSs, immobilized on nanoposts, resembling mushroom structures, allow for reduced substrate coupling and convenient resolution of the modes. Additionally, the modes are studied by in situ extinction acquisitions during nanoparticle synthesis and elucidated by numerical simulations. It is revealed that the broken symmetry by asymmetric particle shape leads to dipolar modes parallel and normal to the base, which are significantly different in terms of energy, excitation dependence on polarization, and particle−particle as well as particle−substrate couplings. In particular, the major parallel mode offers distinct advantages in plasmonics applications over nanospheres. For example, its strong substrate coupling may benefit thin film photovoltaics by efficient light coupling. Higher field concentrations are induced at the sharp edges of a NHS that may enhance hot electron injection in a photocatalyst. Unlike in a spherical dimer, where the field intensity peaks in the middle of the gap, the maximum field in a NHS dimer gap occurs on the metal surface (i.e., at the edges), overlaying with the chemical enhancement. Hence, a higher surface enhancement factor can be achieved in Raman scattering.

Applications of Symmetry Breaking in Plasmonics

“…To finish this mini-review, the last fields of application presented here are chemistry and plasmonic sensing (see Table 4). The first four examples are devoted to chemistry [89][90][91][92], and the last six are dedicated to plasmonic sensing [93][94][95][96][97][98].…”

“…Improved Performances Applications [89] Plasmonic resonances Surface-enhanced Raman scattering sensing [90] Splitting of plasmon modes Sensing [91] Optical properties of 1D plasmonic nanostructures Solution-phase metamaterials [92] Dynamic process of H 2 dissociation on metallic NP Tunable photochemistry [93] Splitting of plasmon modes for alloy nanodisc arrays Biosensing technologies [94] Detection sensitivity Modern biosensors [95] Magnetic Fano resonances Bioanalytics via high precision sensing [96] Detection sensitivity with plasmonic EPs Nanoscale devices and sensors [97] Circular dichroism Detection of chiral molecules [98] Circular dichroism Chiral sensors…”

Light absorption enhancement of ultrathin crystalline silicon solar cells with frequency upconversion layer using silver hemisphere nanoparticles

“…16 Among these various Ag nanoparticles, Ag nanohemispheres (Ag NHs) have attracted a lot of attention for their excellent LSPRs capability caused by multi-photon scattering. [17][18][19] Ag NHs have a high scattering cross section, which can produce a strong LSPR effect when constructed in SCs, and they are easy to prepare in experiments. In this case, rear-located hexagonally packed Ag NHs arrays are applied and integrated on the rear of SCs to improve the light absorption of SCs in long wavelengths.…”

“…Currently, common Ag nanoparticles include nanospheres, 13 nanocylinders, 14 nanocubes, 15 and nanostars 16 . Among these various Ag nanoparticles, Ag nanohemispheres (Ag NHs) have attracted a lot of attention for their excellent LSPRs capability caused by multi-photon scattering 17 – 19 Ag NHs have a high scattering cross section, which can produce a strong LSPR effect when constructed in SCs, and they are easy to prepare in experiments.…”

Standing wave type localized surface plasmon resonance of multifold Ag nanorods

“…It has attracted great attentions on the plasmonic behaviors of nanoparticles with various morphologies, i.e. nanospheres, nanorods, nanostars, nanocrescents, etc [3,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Excitations of LSPR within these nanoparticles could realize light focusing beyond the diffraction limit and generate hot spots on nanoparticle surfaces, where near-field spectrum signals enhancement occur [27,28].…”