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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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Generation of plasmonic hot carriers from d-bands in metallic nanoparticles
摘要： We present an approach to master the well-known challenge of calculating the contribution of d-bands to plasmon-induced hot carrier rates in metallic nanoparticles. We generalize the widely used spherical well model for the nanoparticle wavefunctions to flat d-bands using the envelope function technique. Using Fermi’s golden rule, we calculate the generation rates of hot carriers after the decay of the plasmon due to transitions either from a d-band state to an sp-band state or from an sp-band state to another sp-band state. We apply this formalism to spherical silver nanoparticles with radii up to 20 nm and also study the dependence of hot carrier rates on the energy of the d-bands. We find that for nanoparticles with a radius less than 2.5 nm, sp-band state to sp-band state transitions dominate hot carrier production, while d-band state to sp-band state transitions give the largest contribution for larger nanoparticles.
关键词： Fermi’s golden rule,plasmonic hot carriers,spherical well model,silver nanoparticles,d-bands,metallic nanoparticles,envelope function technique
更新于2025-09-23 15:19:57
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Investigation of Non-ideality Factors for a P3HT: PCBM Based Bulk Heterojunction Organic Solar Cell in Presence of Silver Nanoparticles
摘要： Solar cells are a potential option to meet the growing energy requirements of humans. Organic solar cells (OSCs) represent a class of solar cells that is a part of the third generation solar cell technology. The quest for obtaining enhanced OSC efficiencies has led to the incorporation of metallic nanoparticles (NPs) in the OSCs. Metallic NPs increase the incident light absorption instances, thus increasing the obtainable cell efficiencies. Different parameters and factors need to be considered for obtaining the optimum NP specifications. Investigations of the mechanism of light absorption after the introduction of NPs in the OSC are critical. Hence theoretical simulations for such OSCs are important. An overview of the different solar cell characterization techniques is presented in this paper. Simulations are carried out for these characterization techniques to study the behavior of the P3HT:PCBM based OSC in which silver NPs are incorporated in the active layer. The simulations are carried out for the cell structure in the presence of different non-ideality factors. The non-idealities include mobility limitations, presence of traps, recombination losses, low generation, presence of non-ideal values of series and shunt resistances, the effect of doping, etc. The simulated characterization techniques can be utilized for the performance study and parameter extraction of these NP incorporated OSCs.
关键词： Absorption,Metallic nanoparticles,Active layer,Bulk heterojunction,Cell characterization,Organic solar cell
更新于2025-09-23 15:19:57
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Plasmon lifetime enhancement in a bright-dark mode coupled system
摘要： Metallic nanoparticles can localize the incident light to hot spots as plasmon oscillations, where the intensity can be enhanced by up to four orders of magnitude. Even though the lifetime of plasmons is typically short, it can be increased via interactions with quantum emitters, e.g., spaser nanolasers. However, molecules can bleach in days. Here, we study the lifetime enhancement of plasmon excitations due to the coupling with longer-lifetime dark plasmon modes. We apply an analytical model based on harmonic oscillators to demonstrate that a coupled system of bright and dark plasmon modes decays more slowly than the bright mode alone. Furthermore, exact solutions of the three-dimensional Maxwell equations, i.e., finite-difference time domain, demonstrate that the lifetime of the coupled system significantly increases at the hot spot, which is not predictable by far-field response. The decay of the overall energy of such a coupled system, which can be extracted from experimental absorption measurements, is substantially different from the decay of the hot spot field. This observation enlightens the plasmonic applications in which the hot spot intensity enables the detection of the optical responses.
关键词： bright-dark mode coupling,finite-difference time domain,metallic nanoparticles,plasmon lifetime,hot spot
更新于2025-09-19 17:13:59
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Plasmonic Response of Light-Activated, Nano-Gold Doped Polymers
摘要： Incorporation of metallic nanoparticles (NPs) in polymer matrix has been used to enhance and control dissolution and release of drugs, for targeted drug delivery, as antimicrobial agents, localized heat sources, and for unique optoelectronic applications. Gold NPs in particular exhibit a plasmonic response that has been utilized for photothermal energy conversion. Because plasmonic nanoparticles typically exhibit a plasmon resonance frequency similar to the visible light spectrum, they present as good candidates for direct photothermal conversion with enhanced solar thermal efficiency in these wavelengths. In our work, we have incorporated ~3-nm-diameter colloidal gold (Auc) NPs into electrospun polyethylene glycol (PEG) fibers to utilize the nanoparticle plasmonic response for localized heating and melting of the polymer to release medical treatment. Auc and Auc in PEG (PEG+Auc) both exhibited a minimum reflectivity at 522 nm or approximately green wavelengths of light under ultraviolet-visible (UV-Vis) spectroscopy. PEG+Auc ES fibers revealed a blue shift in minimum reflectivity at 504 nm. UV-Vis spectra were used to calculate the theoretical efficiency enhancement of PEG+Auc versus PEG alone, finding an approximate increase of 10 % under broad spectrum white light interrogation, and ~14 % when illuminated with green light. Auc enhanced polymers were ES directly onto resistance temperature detectors and interrogated with green laser light so that temperature change could be recorded. Results showed a maximum increase of 8.9 °C. To further understand how gold nanomaterials effect the complex optical properties of our materials, spectroscopic ellipsometry was used. Using spectroscopic ellipsometry and modeling with CompleteEASE? software, the complex optical constants of our materials were determined. The complex optical constant n (index of refraction) provided us with optical density properties related to light wavelength divided by velocity, and k (extinction coefficient) was used to show the absorptive properties of the materials.
关键词： spectroscopic ellipsometry,photothermal energy conversion,polyethylene glycol,metallic nanoparticles,plasmonic response,UV-Vis spectroscopy,gold NPs,electrospun fibers
更新于2025-09-16 10:30:52
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[IEEE 2019 Novel Intelligent and Leading Emerging Sciences Conference (NILES) - Giza, Egypt (2019.10.28-2019.10.30)] 2019 Novel Intelligent and Leading Emerging Sciences Conference (NILES) - Conical and Cylindrical Metallic Nanoparticles Design for Plasmonic Photovoltaics Enhancement
摘要： Plasmonic Photovoltaics are considered as a promising candidate for enhancing the optical absorption by embedding metallic nanoparticles that confine the incident light in the cell. This results in thin-film PVs with improved efficiency. In this paper, the effects of embedding both conical and cylindrical metal nanoparticles in plasmonic PVs are investigated. The extinction cross sections for these designs are calculated. The improvement of the optical absorption of the solar cell due to these nanoparticles is proved and compared. Finally, the effects of the design parameters of these nanoparticles are studied. All these simulations are done for PV hosting material of amorphous silicon (a-Si).
关键词： plasmonics,metallic nanoparticles,photovoltaics,localized surface plasmon
更新于2025-09-12 10:27:22
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Size-dependent dielectric function for electron-energy-loss spectra of plasmonic nanoparticles
摘要： A size-dependent complex dielectric function is proposed to describe the impact that size effects have on the dielectric response for electron energy loss spectroscopy (EELS) of plasmonic nanoparticles. Our implementation is based on experimental bulk complex refractive index and the modification of the Lorentz-Drude model. Our theoretical framework is verified and analysed by performing numerical simulation comparisons of EELS for Au spherical nanoparticles of different sizes. The results show that finite-size effects cannot be neglected for a broader size range of up to at least 200 nm for Au spherical nanoparticles. Moreover, the EELS regions in which contributions of surface or bulk energy loss are dominant are confirmed by the optical extinction spectra of Au spherical nanoparticles of different sizes, which takes into account the size-dependent dielectric function. The results provided here provide a suitable and versatile framework for the design of plasmonic elements on the nanometre scale.
关键词： metallic nanoparticles,Plasmonics,size-dependent dielectric function,surface plasmon,electron energy loss spectroscopy (EELS)
更新于2025-09-12 10:27:22
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Biocompatible Gold Nanorod Conjugates for Preclinical Biomedical Research
摘要： Gold nanorods with a peak absorption wavelength of 760 nm were prepared using a seed-mediated method. A novel protocol has been developed to replace hexadecyltrimethylammonium bromide on the surface of the nanorods with 16-mercaptohexadecanoic acid and metoxy-poly(ethylene glycol)-thiol, and the monoclonal antibody HER2. The physical chemistry properties of the conjugates were monitored through optical and zeta-potential measurements to confirm surface chemistry changes. The efficiency of the modifications was quantified through measurement of the average number of antibodies per gold nanorod. The conjugates were investigated for different cells lines: BT-474, MCF7, MCF10, MDCK, and fibroblast. The results show successful cell accumulation of the gold nanorod HER2 conjugates in cells with HER2 overexpression. Incubation of the complexes in heparinized mouse blood demonstrated the low aggregation of the metallic particles through stability of the spectral properties, as verified by UV/VIS spectrometry. Cytotoxicity analysis with LDH release and MTT assay confirms strong targeting and retention of functional activity of the antibody after their conjugation with gold nanorods. Silver staining confirms efficient specific binding to BT-474 cells even in cases where the nanorod complexes were incubated in heparinized mouse blood. This is confirmed through in vivo studies where, following intravenous injection of gold nanorod complexes, silver staining reveals noticeably higher rates of specific binding in mouse tumors than in healthy liver. The conjugates are reproducible, have strong molecular targeting capabilities, have long term stability in vivo and can be used in pre-clinical applications. The conjugates can also be used for molecular and optoacoustic imaging, quantitative sensing of biological substrates, and photothermal therapy.
关键词： Metallic nanoparticles,Gold nanorod fabrication,Cell particle targeting,Gold surface modification,Biocompatible targeting agent,Antibody conjugation
更新于2025-09-10 09:29:36
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Surface Plasmon Resonances in Silver Nanostars
摘要： The recent development of silver nanostars (Ag-NSs) is promising for improved surface-enhanced sensing and spectroscopy, which may be further exploited if the mechanisms behind the excitation of localized surface plasmon resonances (LSPRs) are identified. Here, we show that LSPRs in Ag-NSs can be obtained with finite-difference time-domain (FDTD) calculations by considering the nanostars as combination of crossed nanorods (Ag-NRs). In particular, we demonstrate that an apparent tail at large wavelengths (λ (cid:38) 700 nm) observed in the extinction spectra of Ag-NSs is due to a strong dipolar plasmon resonance, with no need to invoke heterogeneity (different number of arms) effects as is normally done in the literature. Our description also indicates a way to tune the strongest LSPR at desired wavelengths, which is useful for sensing applications.
关键词： Ag nanostars,metallic nanoparticles,plasmonic biosensing
更新于2025-09-10 09:29:36
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Copolymer template etching for Au nanoparticles self-assembly
摘要： In this paper, we report a study on self-assembly of Au colloids assisted by polystyrene (PS)-polymethyl methacrylate (PMMA) block copolymer templates. Etching PMMA cylindrical domains of PS-PMMA thin films provides large-scale arrays of holes in which 12nm Au colloids may fall into. We demonstrate that the holes’ functionalisation with aminosilanes favours the deposition of the Au colloids into the holes. The extinction spectroscopy measurements demonstrate that the Au NPs which are self-assembled using this process do not present any aggregation. Such a process should pave the way for designing plasmonic devices like optical nanosensors.
关键词： optical nanosensor,localised surface plasmon resonance,copolymer template,metallic nanoparticles,self-assembly
更新于2025-09-09 09:28:46