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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Core-shell metallic alloy nanopillars-in-dielectric hybrid metamaterials with magneto-plasmonic coupling

Combining plasmonic and magnetic properties, namely magneto-plasmonic coupling, inspires great research interest and the search for magneto-plasmonic nanostructure becomes considerably critical. In this work, we designed a nanopillar-in-matrix structure with core–shell alloyed nanopillars for both BaTiO 3 (BTO)-Au 0.5 Co 0.5 (AuCo) and BTO-Au 0.25 Cu 0.25 Co 0.25 Ni 0.25 (AuCuCoNi) hybrid systems, i.e., ferromagnetic alloy cores (e.g., Co or CoNi) with plasmonic shells (e.g., Au or Au/Cu). These core–shell alloy nanopillars are uniformly embedded into a dielectric BTO matrix to form a vertically aligned nanocomposite (VAN) structure. Both hybrid systems present excellent epitaxial quality and interesting multi-functionality, e.g., high magnetic anisotropy, magneto-optical coupling response, tailorable plasmonic resonance wavelength, tunable hyperbolic properties and strong optical anisotropy. These alloyed nanopillars-in-matrix designs provide enormous potential for complex hybrid material designs with multi-functionality and demonstrate strong interface enabled magneto-plasmonic coupling along with plasmonic and magnetic performance.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Theoretical Investigations on the Plasmon-Mediated Dissociation of Small Molecules in the Presence of Silver Atomic Wires

Plasmonic nanoparticles can promote bond activation in adsorbed molecules under relatively benign conditions via excitation of the nanoparticle’s plasmon resonance. As the plasmon resonance often falls within the visible light region, plasmonic nanomaterials are a promising class of catalysts. However, the exact mechanisms through which plasmonic nanoparticles activate the bonds of nearby molecules are still unclear. Herein, we evaluate Ag 8 –X 2 (X = N, H) model systems via real-time time-dependent density functional theory (RT-TDDFT), linear response time-dependent density functional theory (LR-TDDFT), and Ehrenfest dynamics in order to better understand the bond activation processes of N 2 and H 2 facilitated by the presence of the atomic silver wire under excitation at the plasmon resonance energies. We find that dissociation is possible for both small molecules at high electric field strength. Activation of each adsorbate is symmetry- and electric field-dependent, and H 2 activates at lower electric field strengths than N 2 . Furthermore, this work serves as a step toward understanding the complex time-dependent electron and electron–nuclear dynamics between plasmonic nanowires and adsorbed small molecules.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Real-space simulations of the hyperbolic plasmon polaritons in 1T′ tungsten ditelluride

Recent discoveries of hyperbolic surface plasmon polaritons (SPPs) in 1T′ WTe 2 have garnered significant attention in 2D materials and nanophotonics. In this study, we employ finite-element simulations to investigate the real-space characteristics of hyperbolic SPPs in thin WTe 2 flakes. Our results show that the SPPs exhibit a pronounced sensitivity to excitation energy and sample thickness. By analyzing the plasmonic field patterns, we extract key plasmonic parameters including plasmon wavelengths, hyperbolic angles, and plasmonic figures of merit. In addition, we examine SPP modes in stacked WTe 2 flakes with varying twist angles, demonstrating that the plasmonic field patterns can be effectively tuned by adjusting the twist angle. Notably, as the twist angle increases, the SPPs undergo a topological transition from open hyperbolic modes to closed elliptic modes. This twist-engineering capability offers promising potential for the development of tunable plasmonic devices based on WTe 2 .

2D materials↗
DOE OSTI2022

Quantum states of cylindrical surface charge density for modeling plasmonic circuit elements: Nanowires, nanorods, cavities, and waveguides

Nanostructures in the form of ellipsoids, prolate spheroids, rings, and cylinders are known to exhibit resonant surface and cavity modes with applications in nanophotonics and plasmonics and, more recently, in novel quantum experiments, in which control of plasmons and their interactions with plasmons, photons, phonons, excitons, and quantum emitters are desired. Nanorods and nanowires are examples of plasmonic structures with spectral properties of potential use as interconnects and circuit components. Additionally, estimates of the surface properties of these components are needed in circuit design and integrated systems. Here, we present a quantum Hamiltonian for the cylindrical surface charge density. We then study the photon excitation of plasmons on the cylindrical surface and calculate their scattering and radiative decay rate. Nonradiative decay of plasmons induces an efficient heating of the nanoparticle and can photoacoustically excite mechanical oscillations. Computational calculations are also presented for the plasmonic modes and the ensuing excitations of nanomechanical eigenmodes of nanoparticles with near-cylindrical symmetries.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Sustainable chemistry with plasmonic photocatalysts

There is a pressing global need to increase the use of renewable energy sources and limit greenhouse gas emissions. Towards this goal, highly efficient and molecularly selective chemical processes that operate under mild conditions are critical. Plasmonic photocatalysis uses optically resonant metallic nanoparticles and their resulting plasmonic, electronic, and phononic light-matter interactions to drive chemical reactions. The promise of simultaneous high-efficiency and product-selective reactions with plasmon photocatalysis provides a compelling opportunity to rethink how chemistry is achieved. Plasmonic nanoparticles serve as nanoscale ‘antennas’ that enable strong light–matter interactions, surpassing the light-harvesting capabilities one would expect purely from their size. Complex composite structures, combining engineered light harvesters with more chemically active components, are a focal point of current research endeavors. In this review, we provide an overview of recent advances in plasmonic catalysis. We start with a discussion of the relevant mechanisms in photochemical transformations and explain hot-carrier generation and distributions from several ubiquitous plasmonic antennae. Then we highlight three important types of catalytic processes for sustainable chemistry: ammonia synthesis, hydrogen production and CO 2 reduction. To help elucidate the reaction mechanism, both state-of-art electromagnetic calculations and quantum mechanistic calculations are discussed. This review provides insights to better understand the mechanism of plasmonic photocatalysis with a variety of metallic and composite nanostructures toward designing and controlling improved platforms for green chemistry in the future.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Possible Realization of Hyperbolic Plasmons in Few-Layered Rhenium Disulfide

Hyperbolic plasmons are a highly desired property in optoelectronics and biomolecular sensing. The necessary condition to realize hyperbolic plasmons is a significant anisotropy of the principal components of the dielectric function, such that at a certain frequency range, one component is negative and the other is positive, i.e., one component is metallic, and the other one is dielectric. Here, we study the effect of anisotropy in ReS 2 , and our theory shows that ReS 2 can host hyperbolic plasmons in the ultraviolet frequency range. The operating frequency range of the hyperbolic plasmons can be tuned with the number of ReS 2 layers. However, we note that the significantly large imaginary part of the macroscopic dielectric response in all layered variants of ReS 2 can result in substantial losses for the hyperbolic plasmons, as in the case with other known hyperbolic materials, with the exception of MoOCl 2 . We also note that ReS 2 hosts ultraviolet hyperbolic plasmons while ZrSiSe, WTe 2 , and CuS nanocrystals host infrared plasmons, providing a novel platform for optoelectronics in the ultraviolet range.

36 MATERIALS SCIENCE↗
NASA NTRS2005

Voltage-induced broad-spectrum reflectivity change with surface-plasmon waves

Voltage-induced broad-spectrum reflectivity change with surface-plasmon waves is reported. When white light is incident at a metal/electro-optical material interface, surface-plasmon waves can be excited under phase match conditions. This surface-plasmon resonance depends on the dielectric constants of both the metal and the electro-optical material. Photons in the surface-plasmon resonance wavelength range are absorbed by the interface. Since metals have large imaginary parts of their dielectric constants, the surface-plasmon resonances are broad and may cover all visible wavelengths. Applying voltage to the electro-optical material to change its dielectric constant can result in a change in the reflectivity at the interface. Experimental results showed a reflectivity change from almost 0% to about 40% under an applied voltage using a liquid-crystal and nickel film structure, and the results had good agreement with theoretical calculations. The theoretical calculations also predicted a 90% reflectivity recovery by exciting surface-plasmon waves at a Rh-Al/electro-optical material interface. These results demonstrate that a high efficiency white light modulator can be built using surface-plasmon excitations.

white light modulator↗
DOE OSTI2022

Near–Band–Edge Enhancement in Perovskite Solar Cells via Tunable Surface Plasmons

Plasmonic perovskite solar cells (PSCs) using core-shell type plasmonic particles are designed, which possess the plasmon resonance in the near-infrared range. This can selectively strengthen the interaction of the perovskite layer with low-energy photons. The mesoporous PSCs employing the plasmonic particles have delivered a 10%-15% enhancement of external quantum efficiency in the plasmonic resonance range. This surface-plasmonic effect has been analyzed using complementary techniques, including selective wavelength excitation and time-dependent photoluminescence. Here it is shown that the metal-based core-shell-type plasmonic structures in PSCs optimize the scattering and absorption of incident light and the dynamics of photogenerated carriers. Furthermore, both optical and electronic effects increase the power conversion efficiency of PSCs from 17.49% to 19.88%, paving a way toward controlling the thickness of the photoactive layer for advanced devices such as tandem solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Elucidating the Roles of Local and Nonlocal Rate Enhancement Mechanisms in Plasmonic Catalysis

Plasmonic metal nanoparticles (e.g., Ag, Au, and Cu) constitute a class of materials that interact with light via the excitation of localized surface plasmon resonance (LSPR). Numerous studies have reported substantial enhancements in the rates of chemical reactions on illuminated plasmonic nanoparticle catalysts compared to corresponding systems in the absence of illumination. There are two mechanisms that have been proposed to explain the LSPR-induced chemical reactivity. One mechanism assumes a local plasmon-induced hot charge-carrier-mediated activation of the reactants, while the other assumes an LSPR-induced equilibrium heating of the catalyst, which leads to energy transfer to and chemical reaction of the adsorbed reactants. Here, in this contribution, we developed a setup amenable to accurate in situ catalyst temperature and kinetic reaction rate measurements. We employed this setup to study the LSPR-induced rate enhancement in a case study of the CO oxidation reaction on plasmonic, monometallic Ag nanoparticle catalysts supported on α-Al 2 O 3 . We explored various Ag loadings and clustering levels. Our data show that the equilibrium heating of the catalyst cannot fully explain the illumination-induced plasmonic rate enhancements. This is the case even for high loading and clustering of Ag nanoparticles, where the equilibrium heating significantly increases. Based on the analysis, we propose that local effects, related to the plasmon-induced activation of adsorbates (reactants) via electronic excitation of the reactant or photothermal heating of the reactants that is highly localized to the individual nanoparticles, play a critical role in driving LSPR-induced chemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Plasmon–emitter interactions at the nanoscale

Plasmon–emitter interactions are of central importance in modern nanoplasmonics and are generally maximal at short emitter–surface separations. However, when the separation falls below 10–20 nm, the classical theory deteriorates progressively due to its neglect of quantum effects such as nonlocality, electronic spill-out, and Landau damping. Here we show how this neglect can be remedied in a unified theoretical treatment of mesoscopic electrodynamics incorporating Feibelman d -parameters. Our approach incorporates nonclassical resonance shifts and surface-enabled Landau damping—a nonlocal damping effect—which have a dramatic impact on the amplitude and spectral distribution of plasmon–emitter interactions. We consider a broad array of plasmon–emitter interactions ranging from dipolar and multipolar spontaneous emission enhancement, to plasmon-assisted energy transfer and enhancement of two-photon transitions. The formalism gives a complete account of both plasmons and plasmon–emitter interactions at the nanoscale, constituting a simple yet rigorous platform to include nonclassical effects in plasmon-enabled nanophotonic phenomena.

Science & Technology - Other Topics↗
DOE OSTI2023

Optical N-plasmon: topological hydrodynamic excitations in graphene from repulsive Hall viscosity

Abstract Edge states occurring in Chern and quantum spin-Hall phases are signatures of the topological electronic band structure in two-dimensional (2D) materials. Recently, a new topological electromagnetic phase of graphene characterized by the optical N-invariant was proposed. Optical N-invariant arises from repulsive Hall viscosity in hydrodynamic many-body electron systems, distinct from the Chern and Z 2 invariants. In this paper, we introduce the topologically protected edge excitation—optical N-plasmon of interacting many-body electron systems in the topological optical N-phase. These optical N-plasmons are signatures of the topological plasmonic band structure in 2D materials. We demonstrate that optical N-plasmons exhibit unique dispersion relations, stability against various boundary conditions, and edge profiles when compared with the topologically trivial edge magneto plasmons. Based on the optical N-plasmon, we design an ultra sub-wavelength broadband topological hydrodynamic circulator, which is a chiral quantum radio-frequency circuit component crucial for information routing and interfacing quantum–classical computing systems. Furthermore, we reveal that optical N-plasmons can be effectively tuned by the neighboring dielectric environment without breaking the topological properties. Our work provides a smoking gun signature of topological electromagnetic phases occurring in 2D materials arising from repulsive Hall viscosity.

Physics↗
DOE OSTI2020

Enhancing Graphene Plasmonic Device Performance via its Dielectric Environment

Graphene plasmons provide a compelling avenue toward chip-scale dynamic tuning of infrared light. Dynamic tunability emerges through controlled alterations in the optical properties of the system defining graphene’s plasmonic dispersion. Typically, electrostatic induced alterations of the carrier concentration in graphene working in conjunction with mobility have been considered the primary factors dictating plasmonic tunability. We find here that the surrounding dielectric environment also plays a primary role, dictating not just the energy of the graphene plasmon but so too the magnitude of its tuning and spectral width. To arrive at this conclusion, poles in the imaginary component of the reflection coefficient are used to efficiently survey the effect of the surrounding dielectric on the tuning of the graphene plasmon. By investigating several common polar materials, optical phonons (i.e., the Reststrahlen band) of the dielectric substrate are shown to appreciably affect not only the plasmon’s spectral location but its tunability, and its resonance shape as well. In particular, tunability is maximized when the resonances are spectrally distant from the Reststrahlen band, whereas sharp resonances (i.e., high-Q) are achievable at the band’s edge. Overall, these observations both underscore the necessity of viewing the dielectric environment in aggregate when considering the plasmonic response derived from two-dimensional materials and provide heuristics to design dynamically tunable graphene-based infrared devices.

36 MATERIALS SCIENCE↗
DOE OSTI2021

First-principles modeling of plasmons in aluminum under ambient and extreme conditions

The theoretical understanding of plasmon behavior is crucial for an accurate interpretation of inelastic scattering diagnostics in many experiments. In this work, we highlight the utility of linear response time-dependent density functional theory (LR-TDDFT) as a first-principles framework for consistently modeling plasmon properties. We provide a comprehensive analysis of plasmons in aluminum from ambient to warm dense matter conditions and assess typical properties such as the dynamical structure factor, the plasmon dispersion, and the plasmon lifetime. We compare our results with scattering measurements and with other TDDFT results as well as models such as the random phase approximation, the Mermin approach, and the dielectric function obtained using static local field corrections of the uniform electron gas parametrized from path-integral Monte Carlo simulations. We conclude that results for the plasmon dispersion and lifetime are inconsistent between experiment and theories and that the common practice of extracting and studying plasmon dispersion relations is an insufficient procedure to capture the complicated physics contained in the dynamic structure factor in its full breadth.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Plasmon-Induced Resonance Energy Transfer in Hybrid Nanomaterials

Plasmon-induced resonance energy transfer (PIRET) has emerged as a powerful mechanism for harnessing and redirecting plasmon energy before it dissipates into hot carriers or heat. By matching plasmon resonance frequencies with acceptor absorption bands, PIRET extends plasmon-driven processes beyond the charge transfer pathway, enabling selective energy flow into excitonic transitions. Here, this review highlights important progress in elucidating the fundamental plasmon decay processes and transitioning them into hybrid nanomaterials under PIRET. Employing specialized single-particle spectroscopic techniques based on scattering, extinction, and emission enables demonstration of PIRET in the face of competing mechanisms, such as interfacial charge transfer and thermalization. Finally, we complete this review by addressing strategies for active modulation of PIRET and present applications, ranging from plasmon photocatalysis to intracellular biochemical sensing.

Energy transfer↗
DOE OSTI2025

Hybrid Plasmonic Coupled‐Mode Metasurface Design for Shot‐Noise Limited Ppb‐Level Hydrogen Detection

Plasmonic hydrogen sensors have enabled hydrogen detection below parts-per-million (ppm) range by boosting the sensitivity using localized surface plasmonic resonant (LSPR) structures. However, the intrinsic optical losses of Palladium (Pd), the primary plasmonic metal used for hydrogen detection, result in a low quality (Q) factor LSPR, which fundamentally hinders further improvement. In this work, a hybrid plasmonic metasurface is proposed that couples Pd-based LSPR structure with an Au film supporting surface plasmon polariton mode (Au-SPP). The coupled near-perfect absorber resonance yields a spectrally narrow, high Q response that retains strong sensitivity to hydrogen while improving resonance localization. Numerical analysis shows that, under shot-noise-limited conditions, the limit of detection (LoD) can be improved by over threefold compared to the state-of-the-art designs. Furthermore, this hybrid plasmonic coupled-mode metasurface thus presents a promising pathway to achieve parts-per-billion-level (ppb-level) hydrogen detection with enhanced spectral precision and robustness.

coupled modes↗
DOE OSTI2021

Ultrafast Carrier and Lattice Dynamics in Plasmonic Nanocrystalline Copper Sulfide Films

Excited carrier dynamics in plasmonic nanostructures determines many important optical properties such as nonlinear optical response and photocatalytic activity. Here it is shown that mesoscopic plasmonic covellite nanocrystals with low free-carrier concentration exhibit a much faster carrier relaxation than in traditional plasmonic materials. A nonequilibrium hot-carrier population thermalizes within first 20 fs after photoexcitation. A decreased thermalization time in nanocrystals compared to a bulk covellite is consistent with the reduced Coulomb screening in ultrathin films. The subsequent relaxation of thermalized, equilibrium electron gas is faster than in traditional plasmonic metals due to the lower carrier concentration and agrees well with that in a bulk covellite showing no evidence of quantum confinement or hot-hole trapping at the surface states. The excitation of coherent optical phonon modes in a covellite is also demonstrated, revealing coherent lattice dynamics in plasmonic materials, which until now was mainly limited to dielectrics, semiconductors, and semimetals. These findings show advantages of this new mesoscopic plasmonic material for active control of optical processes.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Low‐Loss Tunable Infrared Plasmons in the High‐Mobility Perovskite (Ba,La)SnO 3

Abstract BaSnO 3 exhibits the highest carrier mobility among perovskite oxides, making it ideal for oxide electronics. Collective charge carrier oscillations known as plasmons are expected to arise in this material, thus providing a tool to control the nanoscale optical field for optoelectronics applications. Here, the existence of relatively long‐lived plasmons supported by high‐mobility charge carriers in La‐doped BaSnO 3 (BLSO) is demonstrated. By exploiting the high spatial and energy resolution of electron energy‐loss spectroscopy with a focused beam in a scanning transmission electron microscope, the dispersion, confinement ratio, and damping of infrared localized surface plasmons (LSPs) in BLSO nanoparticles are systematically investigated. It is found that LSPs in BLSO exhibit a high degree of spatial confinement compared to those sustained by noble metals and have relatively low losses and high quality factors with respect to other doped oxides. Further analysis clarifies the relation between plasmon damping and carrier mobility in BLSO. The results support the use of nanostructured degenerate semiconductors for plasmonic applications in the infrared region and establish a solid alternative to more traditional plasmonic materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Plasmon-Assisted Electrochemical Epoxidation using Water as an Oxidant

Olefin epoxidation, an important industrial reaction, often uses hazardous oxidants, causing challenges in waste disposal. Here, we demonstrate the use of water as an oxidant by a plasmon-assisted electrochemical strategy. The electrocatalyst is comprised of a hybrid of a water oxidation catalyst, manganese oxide, and plasmonic gold nanoparticles. Visible-light irradiation of the electrocatalyst enhanced the epoxidation of 4-styrenesulfonate 5-fold as compared to dark conditions at the same temperature. From electrochemical analyses conducted under plasmon excitation conditions, complemented by real-time time-dependent density functional tight binding simulations, it is found that the plasmonic boost of the electrochemical styrene epoxidation is due to energetic holes generated by the excitation of localized surface plasmon resonances of gold nanoparticles. These photogenerated holes activate adsorbed water for oxidation and enhance the binding of 4-styrenesulfonate at interfacial sites. Here, this work demonstrates a proof of concept and establishes the mechanistic basis for plasmon-assisted activation of water as an O atom source for electrochemical epoxidations.

Gold↗