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Numerical Modeling of Acousto-Plasmonic Coupling in Metallic Nanoparticles
摘要： We describe a computational approach to study the acousto-plasmonic coupling in metallic nanoparticles. We use the high level multiphysics finite element software FreeFEM developed at Laboratoire Jacques-Louis Lions of Pierre and Marie Curie University (Paris). Our numerical method determines one after the other the acoustic modes of the nanoparticles and the modulation of the electromagnetic properties. The transfer of the deformed geometries between acoustic and electromagnetic simulations is realized by an update of the nodal coordinates situated at the boundary between the nanoparticle and its host medium, and using a mesh deformation algorithm based on radial basis function interpolation. Thus we theoretically investigate different coupling mechanisms between confined vibrations and surface plasmons: shape effect, electron density effect due to changes of the nanoparticle volume and inter-band transitions effect which is evaluated by the deformation potential mechanism.
关键词： acousto-plasmonic coupling,radial basis function interpolation,FreeFEM,finite element method,metallic nanoparticles
更新于2025-09-23 15:21:01
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Plasmonic Coupling of AgNPs near Graphene Edges: A Cross-Section Strategy for High-Performance SERS Sensing
摘要： Fully exploiting plasmonic coupling of nanostructured metals is an effective method to promote surface-enhanced Raman scattering (SERS) performance for trace detection of molecules. Herein, we propose a cross-section strategy to maximize plasmonic coupling of silver nanoparticles (AgNPs) in graphene-based membrane. Specifically, AgNPs are isolated by water-dispersible graphene (W-Gr) and enriched in the vicinity of W-Gr edges when assembling into a macroscopic membrane, thus affording AgNPs on the cross section with uniform and proper gaps in the vertical plane to generate maximal plasmon coupling. Moreover, the superior sensitivity (5×10-13 M for R6G) to most reported graphene-metal structures and the long-term stability against aerobic oxidation jointly make the cross-section of AgNPs/W-Gr membrane a potential SERS substrate for trace-molecule detection. The revealed mechanism for AgNPs enrichment near edges highlights the importance of flow-directed assembly process of W-Gr. This work provides new insight into the interpretation and utilization of two-dimensional materials as building blocks in high-performance SERS sensing.
关键词： Cross-section strategy,AgNPs,SERS sensing,Plasmonic coupling,Graphene edges
更新于2025-09-23 15:19:57
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Plasmonic coupling in closed-packed ordered gallium nanoparticles
摘要： plasmonic gallium (Ga) nanoparticles (nps) are well known to exhibit good performance in numerous applications such as surface enhanced fluorescence and Raman spectroscopy or biosensing. However, to reach the optimal optical performance, the strength of the localized surface plasmon resonances (LSPRs) must be enhanced particularly by suitable narrowing the NP size distribution among other factors. With this purpose, our last work demonstrated the production of hexagonal ordered arrays of Ga NPs by using templates of aluminium (Al) shallow pit arrays, whose LSPRs were observed in the VIS region. The quantitative analysis of the optical properties by spectroscopic ellipsometry confirmed an outstanding improvement of the LSPR intensity and full width at half maximum (FWHM) due to the imposed ordering. Here, by engineering the template dimensions, and therefore by tuning Ga NPs size, we expand the LSPRs of the Ga NPs to cover a wider range of the electromagnetic spectrum from the UV to the IR regions. More interestingly, the factors that cause this optical performance improvement are studied with the universal plasmon ruler equation, supported with discrete dipole approximation simulations. the results allow us to conclude that the plasmonic coupling between nps originated in the ordered systems is the main cause for the optimized optical response.
关键词： plasmonic coupling,gallium nanoparticles,spectroscopic ellipsometry,discrete dipole approximation,localized surface plasmon resonances
更新于2025-09-19 17:13:59
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Broadband plasmonic coupling and enhanced power conversion efficiency in luminescent solar concentrator
摘要： Advancements in solar energy harvesting technologies call for innovative approaches to meet the ever-growing energy demand. This study exploits the plasmonic interaction of metal nanoparticles (MNPs) with fluorophores to improve the optical performance of Luminescent Solar Concentrators (LSCs). Plasmonic Luminescent Solar Concentrator (PLSC) with dimensions of 45 × 45 × 3 mm3 containing Lumogen Red305 dye and gold core silver shell nanocuboids (Au@Ag NCs) were fabricated and characterized. Plasmonic coupling in the PLSC device was influenced through spacing and spectral overlap between the nanocuboids (NCs) and Red305 dye. The spacing between Au@Ag NCs and Red305 dye was controlled by the doping concentration of Au@Ag NCs for acquiring a homogeneous sample. The optical performance of PLSC waveguides was investigated through edge emission measurements of the waveguides while varying the doping concentration of Au@Ag NCs. A maximum enhancement of 30% in the fluorescence was achieved for PLSC device containing an optimal doping concentration (1.1 ppm) of Au@Ag NCs. A transition from maximum fluorescence enhancement to quenching was demonstrated, emphasizing the importance of MNP doping concentration and spectral overlap when coupling Au@Ag NC and Red305 dye molecules. At high doping concentrations of Au@Ag NCs, non-radiative energy transfer from Red305 dye molecules to the Au@Ag NCs made quenching a dominant effect. Monocrystalline silicon solar cells were attached to one edge of the PLSC waveguides. For the sample with 1.1 ppm Au@Ag NCs doping concentration, the power conversion efficiency was found to be 1.2 times higher than the power conversion efficiency of 0 ppm sample.
关键词： Gold core silver shell nanocuboids,Edge emission,Photon mode density,Luminescent solar concentrator,Surface plasmon resonance,Plasmonic coupling
更新于2025-09-19 17:13:59
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Multiple Fano Resonances with Tunable Electromagnetic Properties in Graphene Plasmonic Metamolecules
摘要： Multiple Fano resonances (FRs) can be produced by destroying the symmetry of structure or adding additional nanoparticles without changing the spatial symmetry, which has been proved in noble metal structures. However, due to the disadvantages of low modulation depth, large damping rate, and broadband spectral responses, many resonance applications are limited. In this research paper, we propose a graphene plasmonic metamolecule (PMM) by adding an additional 12 nanodiscs around a graphene heptamer, where two Fano resonance modes with different wavelengths are observed in the extinction spectrum. The competition between the two FRs as well as the modulation depth of each FR is investigated by varying the materials and the geometrical parameters of the nanostructure. A simple trimer model, which emulates the radical distribution of the PMM, is employed to understand the electromagnetic field behaviors during the variation of the parameters. Our proposed graphene nanostructures might find significant applications in the fields of single molecule detection, chemical or biochemical sensing, and nanoantenna.
关键词： surface plasmon,chemical potential,Fano resonances,graphene metamolecule,modulation depth,plasmonic coupling
更新于2025-09-19 17:13:59
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Collective multipole oscillations direct the plasmonic coupling at the nanojunction interfaces
摘要： We present a systematic study of the effect of higher-multipolar order plasmon modes on the spectral response and plasmonic coupling of silver nanoparticle dimers at nanojunction separation and introduce a coupling mechanism. The most prominent plasmonic band within the extinction spectra of coupled resonators is the dipolar coupling band. A detailed calculation of the plasmonic coupling between equivalent particles suggests that the coupling is not limited to the overlap between the main bands of individual particles but can also be affected by the contribution of the higher-order modes in the multipolar region. This requires an appropriate description of the mechanism that goes beyond the general coupling phenomenon introduced as the plasmonic ruler equation in 2007. In the present work, we found that the plasmonic coupling of nearby Ag nanocubes does not only depend on the plasmonic properties of the main band. The results suggest the decay length of the higher-order plasmon mode is more sensitive to changes in the magnitude of the interparticle axis and is a function of the gap size. For cubic particles, the contribution of the higher-order modes becomes significant due to the high density of oscillating dipoles localized on the corners. This gives rise to changes in the decay length of the plasmonic ruler equation. For spherical particles, as the size of the particle increases (i.e., ≥80 nm), the number of dipoles increases, which results in higher dipole–multipole interactions. This exhibits a strong impact on the plasmonic coupling, even at long separation distances (20 nm).
关键词： plasmonic coupling equation,silver nanoparticle pairs,localized surface plasmon resonance,field enhancement,dipole–multipole interaction
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Effective Coupling of a Plasmonic Nanorod to a Microsphere Resonator
摘要： Coupled photonic-plasmonic systems have already proven successful as ultra-sensitive sensors with the potential of single virus detection. Such systems are e.g. composed of a plasmonic nanoparticle in vicinity of an optical resonator usually in the form of a microsphere, a mirroring or a microdisk. These systems are proven highly sensitive due to their large quality factor and are thus utilized as bio, pressure, gas or temperature sensors. When a plasmonic nanoparticle is positioned near such resonator, coupling of the plasmonic and photonic modes can result in an ultra-sensitive biosensor, since nanoparticle presence enhance ambient refractive index (RI) variation sensitivity. In this paper, photonic-plasmonic coupling of a gold nanorod in close vicinity of a silica microsphere is simulated in order to investigate various types of coupling settings in such systems. The presence of the nanorod results in a frequency shift as well as in a reduction of the quality factor, which are both highly dependent on nanorod properties such as size, distance between the particle and the sphere as well as the nanorod orientation relative to the sphere surface. A single gold nanorod is positioned in 50nm distance to a 15.5μm silica microsphere which supports a whispering gallery mode at 1550nm and both resonance frequency and quality factor are computed using the simulation platform COMSOL Multiphysics. The nanorod orientation is altered starting from the tangential direction with respect to the sphere surface (0o) to the perpendicular direction (90o). In the Fig 1a) the quality factor together with the damping constant is shown as a function of the nanorod orientation for at an operating wavelength of 1550nm. The 90o direction results in higher quality factor as well as a better mode stability although the frequency shift associated to a 90o turn is only about 10GHz. In Fig 1b) the frequency shift and quality factor for the perpendicular nanorod versus ambient medium RI is plotted, which confirms the ultra-sensitivity of the designed optical resonator up to a 10-3 RI shift. The electric field distribution outside and inside of the nanorod is illustrated in Fig. 1c) for the three directions 90o, 45o and 0o where the perpendicular nanorod shows the weakest interaction with the excited whispering gallery mode and thus yields the largest quality factor.
关键词： silica microsphere,photonic-plasmonic coupling,gold nanorod,COMSOL Multiphysics,whispering gallery mode
更新于2025-09-12 10:27:22
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Strong circular dichroism enhancement by plasmonic coupling between graphene and h-shaped chiral nanostructure
摘要： Circular dichroism (CD) is useful in polarization conversion, negative refraction chemical analysis, and bio-sensing. To achieve strong CD signals, researchers constantly break the symmetry of nanostructures. However, how to further enhance the CD based on a new mechanism has become a new challenge in this field. In this work, a hybrid plasmonic chiral system composed of an array of graphene ribbons (GRs) over h-shaped sliver chiral nanostructures (HSCNs) is theoretically investigated. Results demonstrate that the plasmonic coupling between HSCNs and GRs results in different enhanced absorptions for different circularly polarized lights. The absorbance of right circularly polarized light is enhanced to perfect absorption; the absorption of left circularly polarized light is enhanced weakly. It leads to the CD effect of HSCNs@GRs approaching 88%. The loss distributions of HSCNs and HSCNs@GRs reveal that the absorption is enhanced and transferred from HSCNs to GRs. Moreover, the current distributions of HSCNs@GRs are simplified to equivalent LC resonant circuits, which can qualitatively explain the change of CD signals by tuning geometrical parameters of HSCNs@GRs. The findings of this work provide a new method of enhancing chirality and benefit the design of graphene-based chiral optoelectronic devices.
关键词： plasmonic coupling,Circular dichroism,chiral optoelectronic devices,graphene ribbons,h-shaped sliver chiral nanostructures
更新于2025-09-12 10:27:22
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Direct and Label-Free Detection of MicroRNA Cancer Biomarkers Using SERS-Based Plasmonic Coupling Interference (PCI) Nanoprobes
摘要： MicroRNAs (miRNAs), small non-coding endogenous RNA molecules, are emerging as promising biomarkers for early detection of various diseases and cancers. Practical screening tools and strategies to detect these small molecules are urgently needed in order to facilitate the translation of miRNA biomarkers into clinical practice. In this study, a label-free biosensing technique based on surface-enhanced Raman scattering (SERS), referred to as “plasmonic coupling interference (PCI)”, was applied for the multiplex detection of miRNA biomarkers. The sensing mechanism of the PCI technique relies on the formation of a nanonetwork consisting of nanoparticles with Raman labels located between adjacent nanoparticles that are interconnected by DNA duplexes. Due to the plasmonic coupling effect of adjacent nanoparticles in the nanonetwork, the Raman labels exhibit intense SERS signals. Such effect can be modulated by the addition of miRNA targets of interest that act as inhibitors to interfere with the formation of this nanonetwork, resulting in a diminished SERS signal. In this study, the PCI technique is theoretically analyzed and the multiplex capability for detection of multiple miRNA cancer biomarkers is demonstrated, establishing the great potential of PCI nanoprobes as a useful diagnostic tool for medical applications.
关键词： SERS,PCI,miRNAs,cancer biomarkers,MicroRNAs,plasmonic coupling interference,multiplex detection
更新于2025-09-12 10:27:22
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A Study of the Effect of Anisotropic Gold Nanoparticles on Plasmonic Coupling with a Photosensitizer for Antimicrobial Film.
摘要： Development of antimicrobial surfaces for sterilization is much needed to avoid the spreading of drug resistant bacteria. Light can activate antimicrobial surfaces by an interaction between nanoparticles and a photosensitizer dye, to produce a steady and efficient killing of bacteria. The film studied in this work contains gold nanorods (AuNRs) of 32 nm length and 16 nm diameter and gold nanostars (AuNSs) of 50 nm of diameter, in combination with crystal violet dye (CV). The surface plasmon resonance (SPR) of the nanoparticles used in the film was mathematically simulated and characterized to understand difference SPR between the particles. Their effects on plasmonic coupling with the dye, thus the production of reactive oxygen species (ROS) and consequently the activity of the film against bacteria were studied. The films showed great antimicrobial activity against gram negative bacteria (E. coli) in 4 h of light exposure, when modified with AuNSs, it could kill E. coli in 5 orders of magnitudes (5-log) and the one modified with AuNRs could kill with 4 order of magnitudes (4-log). While maintaining partial activity against gram positive bacteria (S. aureus), i.e. being able to kill in 2.5 orders of magnitudes by the film containing AuNSs and 3 orders of magnitudes by those containing AuNRs. The differential response of gram (-) and gram (+) bacteria to the ROS generated by the films, would allow more targeted approach for specific bacterial species, for example, surfaces of bedpans or common contact surfaces (handles, handrails etc.) that are contaminated principally by gram (-) or gram (+) bacteria, respectively.
关键词： anisotropy,light-activated,non-contact sterilization,antimicrobial surface,simulations,Plasmonic coupling
更新于2025-09-12 10:27:22