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At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Highly luminescent ultra-thin films with rare earth for plasmonic applications

Amphiphilic complexes with luminescent rare earth metal ions suitable for Lanmuir-Blodgett (LB) deposition have been synthesized. LB monolayers with closely packed Eu complexes deposited directly on silver demonstrate significant far-field emission in contrast to the theoretical predictions of full quenching. Angular radiation and polarization patterns of the electric and magnetic dipole emission of Eu 3+ point to a high excitation efficiency of surface plasmon polaritons. Different luminescent behavior of closely packed emitters in comparison to diluted systems is tentatively attributed to the collective state of emitters in LB layers formed via near-field coupling with surface plasmons.

Munga, J.↗
DOE OSTI2020

Parametric study of optical transmission through plasmonic hole arrays modulated by the phase transition of vanadium dioxide

We have performed comprehensive electromagnetic simulations and preliminary experiments to explore the effects of geometrical and material parameters on the extraordinary optical transmission (EOT) through periodic arrays of subwavelength holes in a bilayer stack consisting of a gold or silver film atop a vanadium dioxide film (Au/Ag + VO 2 ), where the latter undergoes a semiconductor-to-metal phase transition. Using the finite-difference time-domain (FDTD) and finite-element methods (FEM), we vary iteratively the array periodicity, VO 2 film thickness and hole diameters, as well as the refractive index inside the VO 2 -layer holes and the VO 2 optical constants. For each variation, we compare the metallic-to-semiconducting ratios of the zero-order transmission ( T 00 ) peaks and find sharp maxima in these ratios within narrow parameter ranges. The maxima arise from Fabry-Perot and Fano-type resonances that minimize T 00 in the semiconducting phase of the perforated bilayers. At a fixed array period, the primary factors controlling the VO 2 -enabled EOT modulation are the VO 2 thickness, diameter of the VO 2 -layer holes, and absorption in the two VO 2 phases. Besides uncovering the origins of the higher metallic-phase T 00 , this study provides a protocol for optimizing the performance of the bilayer hole arrays for potential uses as dynamically tunable nano-optical devices.

Donev, Eugenii U. (ORCID:000000030555219X)↗
DOE OSTI2025

Ultrasonic deterrents provide no additional benefit over curtailment in reducing bat fatalities at an Ohio wind energy facility

Wind energy is important for achieving net-zero greenhouse gas emissions but also contributes to global bat mortality. Current strategies to minimize bat mortality due to collision with wind-turbine blades fall broadly into two categories: curtailment (limiting turbine operation during high-risk periods) and deterrence (discouraging bat activity near turbines). Recently, there has been interest in combining these strategies to achieve greater reductions in bat fatalities than either strategy might achieve in isolation. To investigate the effectiveness of combining curtailment with ultrasonic deterrent minimization strategies, we deployed six ultrasonic deterrents at nacelle height on 16 experimental turbines at Avangrid Renewables’ Blue Creek Wind Energy Facility. We rotated between four conditions (normal operations, curtailment only, deterrent only, curtailment and deterrent) randomly assigned to four wind turbines each night between 15 June and 3 October 2017. We found that bat mortality at wind turbines was independent of wind speed. The effectiveness of ultrasonic acoustic deterrents varied between high-frequency-calling species (eastern red bats) and low-frequency-calling species (hoary bats, silver-haired bats, and big brown bats). When deterrents were active, mortality was twice as high for eastern red bats compared to the control. Conversely, deterrents had a weak dampening effect on bat mortality for low-frequency species. We found no additive effects on mortality reduction for turbines operating both curtailment and deterrents compared to either approach in isolation. Our findings suggest that ultrasonic acoustic deterrents may not be effective for both high and low frequency echolocating bats. The increase in fatalities of eastern red bats is alarming and underscores the importance of considering site- and species-specific effects of minimization solutions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2020

Surface plasmon polariton pulse shaping via two-dimensional Bragg grating pairs

Abstract We demonstrate control over the spatial and temporal properties of surface plasmon polaritons (SPPs) launched from nanohole arrays in silver. The arrays provide wave vector matching to allow the conversion of free-space photons into counter-propagating SPPs. SPPs launched from multiple arrays interfere at well-defined spatial positions, and the interference fringes form an all-SPP periodic nano-optical grating which evolves in space and time as the SPPs propagate. The spatio-temporal characteristics of the optical grating can be tuned through various nanohole array parameters such as tilt angle, separation, and array width. In addition, we examine multiperiodic arrays (MPAs) consisting of arrays with different pitches placed adjacent to one another. This platform allows the temporal interference of SPPs with different central wavelengths to be tailored through the MPA geometric and structural parameters. The temporal interference serves as an encoded signal, whereby the frequency components can be controlled by the array properties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Zinc oxide (ZnO) hybrid metasurfaces exhibiting broadly tunable topological properties

Extreme light confinement observed in periodic photonic structures, such as the vortex singularities in momentum (k) space, has been associated with their topological nature. Consequently, by exploiting and tuning their topological properties, optical metasurfaces have been demonstrated as an attractive platform for active photonics. However, given the fact that most active media under external excitations can only provide limited refractive index change, the potential advancements offered by the topological character of active metasurfaces have remained mostly unexplored. Zinc oxide (ZnO), which has recently exhibited optically-induced extraordinarily large permittivity modulations at visible and near-infrared frequencies, is an excellent active material for dynamic metasurfaces exhibiting strong tuning. This work demonstrates that a hybrid metasurface consisting of an array of ZnO nanodisks on a silver backplane displays broadly tunable topological properties. In particular, by performing k-space scattering simulations using measured pump-fluence-dependent material properties of ZnO, we study in detail the light reflection from the hybrid metasurface. Our results validate that the large k-space topology tuning of the metasurface can result in enormously strong polarization manipulation of near-infrared light in the vicinity of the topological features. The observed polarization switching effect is highly sensitive to the polarization and wavelength of an incident wave, owing to the symmetry and dispersion characteristics of the proposed system. Our study indicates that leveraging a combination of the extraordinary material properties and the k-space topology, hybrid metasurfaces based on ZnO may open new avenues for creating all-optical switchable metadevices.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Anomalous dips in reflection spectra of optical polymers deposited on plasmonic metals

Abstract We have studied reflection spectra of dye-doped and undoped polymers deposited onto Ag and Au substrates and found anomalous dips in the UV spectral range. On top of Ag substrates, the λ ∼ 375 nm dips were observed in undoped PMMA, PVP, and PS polymers as well as PMMA doped with Rh590 and HITC laser dyes. In silver-based samples, the spectral positions of the observed reflection dips were close to singularities in the refractive indexes of surface plasmon polaritons (SPPs) propagating at the interface between Ag and polymer. The latter singularities can tentatively explain the λ ∼ 375 nm reflection dips, if the scattering of Ag and polymeric films is large enough to launch SPP without any prism or grating. The dips observed in reflection of Rh590:PMMA and HITC:PMMA on top of Au, were more pronounced than those on Ag, broader, shifted to shorter wavelengths, and their spectral positions had large standard deviations. Furthermore, no anomalous dips in gold-based samples were observed in the reflection spectra of undoped PMMA, PVP, and PS polymers, and a modest singularity in the SPP refractive index, predicted theoretically at λ ∼ 500 nm, cannot explain the dips in the UV reflection spectra observed experimentally. It appears likely that the origin of the reflection dips on top of Au substrates is different from that on top of Ag substrates.

36 MATERIALS SCIENCE↗
DOE OSTI2025

3D-printed mirror-less helicity preserving metasurface “mirror” for THz applications

Stimulated by seminal works on generalized reflection and refraction laws, metasurfaces have evolved to a highly promising research direction, as they allow a multitude of different functionalities by optically thin wave-control elements/structures. Among them, structures functioning in the low THz regime are of extensive research interest, due to their high potential in communication and sensing applications. In this paper we propose a simple THz metasurface design that exhibits ideally perfect cross-polarized reflection for linear polarization and perfect helicity-preserving reflection with a geometric (Pancharatnam–Berry) phase for circular polarization, without the presence of any back-reflector. Numerical calculations demonstrating the structure response are justified by analytical models, which provide physical insights on this response. The designed metasurfaces are fabricated using the direct laser writing 3D-printing technology, metallized with electroless silver plating, and are characterized by THz time domain spectroscopy, with the experimental results validating the corresponding theoretical ones. Applications including beam steering and focusing, exploring the Pancharatnam–Berry phase, are also demonstrated numerically. Besides those applications, the helicity preserving mirror response of our metasurfaces can be valuable, among others, also in molecular chirality sensing applications, an issue that is also highlighted here.

3D-printed metasurfaces↗
DOE OSTI2025

Generation of fast photoelectrons in strong-field emission from metal nanoparticles

We investigated the generation and control of fast photoelectrons (PEs) by exposing plasmonic nanoparticles (NPs) to short infrared (IR) laser pulses with peak intensities between 10 12 and 3 × 10 13 W/cm 2 . Our measured and numerically simulated PE momentum distributions demonstrate the extent to which PE yields and cutoff energies are controlled by the NP size, material, and laser peak intensity. For strong-field photoemission from spherical silver, gold, and platinum NPs with diameters between 10 and 100 nm our results confirm and surpass extremely high PEs cutoff energies, up to several hundred times the incident laser-pulse ponderomotive energy, found recently for gold nanospheres [Saydanzad et al., Nanophotonics 12, 1931 (2023)]. As reported previously for dielectric NPs [Rupp et al., J. Mod. Opt. 64, 995 (2017)], at higher intensities the cutoff energies we deduce from measured and simulated PE spectra tend to converge to a metal-independent limit. We expect these characteristics of light-induced electron emission from prototypical plasmonic metallic nanospheres to promote the understanding of the electronic dynamics in more complex plasmonic nanostructures and the design of nanoscale light-controlled plasmonic electron sources for photoelectronic devices of applied interest.

electron source↗
DOE OSTI2026

Sap Velocity Data for Urban Trees in Chicago, Illinois (2024-2025)

This dataset contains uncorrected sap velocity measurements using the heat ratio method (HRM) collected using ICT International SFM1x sensors at five urban sites in Chicago, Illinois, as part of the DOE CROCUS project. The data includes continuous monitoring of sap velocity from various tree species, including Maples (Acer spp.): Sugar Maple (Acer saccharum), Silver Maple (Acer saccharinum), and Red Maple (Acer rubrum); Oaks (Quercus spp.): Swamp White Oak (Quercus bicolor); American Elm (Ulmus americana); Honey Locust (Gleditsia triacanthos); Cottonwood (Populus deltoides); and Tree of Heaven (Ailanthus altissima) across Chicago State University (CSU), Northeastern Illinois University (NEIU), Northwestern University (NU), University of Illinois Chicago (UIC), and West Woodlawn "Blacks in Green" (BIG). These include both street trees and those in urban park locations. Measurements were collected at 15-20 minute intervals, depending on the sensor, and transmitted via Long Range Wide Area Network (LoRaWAN) protocols. The wireless data was collected by Sage Network (https://sagecontinuum.org/) nodes. The dataset includes sensor ID, Global Positioning System (GPS) coordinates, tree species (common and scientific names), tree identification number, diameter at breast height (DBH in cm), uncorrected sap velocity measurements (cm/hr) from both inner and outer probes, and Sage Node identifiers so the data can be mapped to related variables such as air quality and wind speed that were collected on the Sage nodes. All timestamps are in local Chicago time (CDT/CST). Quality control flags are provided using a 3-bit binary system indicating physical range violations (< -10 or > 60 cm/hr), step spikes (absolute difference > 36 cm/hr), and stuck sensor conditions (> 10 consecutive identical values). These are raw data, not corrected for wood anatomy or species-specific characteristics. Data is provided in comma separated (CSV) format. This dataset is part of a larger collection of CROCUS environmental monitoring data, including linked datasets from Air Quality Transmitter (AQT) sensors, Weather Transmitter (WXT) sensors, and Multi-Function Research LoRaWAN (MFR) Nodes. DOIs for the supporting data are provided as part of this data package.

Chicago↗
DOE OSTI2024

Plasmonic surface lattice resonances in nanoparticle arrays

This work reviews the literature and provides a detailed computational analysis of the optical properties of one- and two-dimensional arrays of silver and gold nanoparticles, with emphasis on surface lattice resonances (SLRs) that arise when localized plasmon resonances (LSPRs) in the nanoparticles couple to diffraction resonances that are determined by the interparticle spacing to give polariton modes in which the two types of excitations are coherently coupled. The computations are based on the coupled dipole approximation, which provides a nearly quantitative description of the extinction spectra for arrays of this type where the particles are well separated and not too large. The computations are used to determine many characteristics of SLRs associated with the lower polariton mode that is mostly photonic in nature, and we also study the upper polariton that is dominated by the LSPR response, as well as Rayleigh anomalies (RAs) that correspond to purely diffractive excitation. The calculations explore the sensitivity of these excitations to the directions of the incident wave and polarization vectors relative to the array axis, the effect of array spacing and number of particles in the array, and the effect of nanoparticle radius and background refractive indices. Details of the physical mechanisms involved in determining blue- and/or redshifts as structural parameters are varied is provided, with SLR’s being sensitive to far-field coupling, while LSPR’s can also be sensitive to near- and intermediatefield interactions that in some cases are similar to effects found in dye molecule aggregates.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Life cycle cost assessment of material recovery from perovskite solar cells

Perovskite photovoltaic (PV) cells have created a significant interest over the last few years due to their low-cost and high-power conversion efficiencies. While perovskite PVs are still under development, we analyze cost of alternative sustainable end-of-life management for perovskite PV cells; this allows to reuse economically valuable materials and prevent environmental contamination. Here, we studied the life cycle cost assessment of recovering metals such as lead, aluminum, gold, nickel, and silver and other valuable materials such as glass from waste perovskite PVs. We also developed a recycling scheme to optimize the material recovery and determine the economically feasible ways to separate the cells layer-by-layer. Further, we assessed the cost and the net cost of the perovskite PV recycling processes. We found that the most feasible recycling technique’ cost is $\$$10.70 and its net cost is $\$$– 2.95 per 1 m 2 module. These values could be further improved by optimizing and reusing chemicals involved in process. These results indicate that the cost of perovskite PV recycling is economically feasible and there is potentional to gain benefit from sustainable end-of-life management of perovskite PVs.

14 SOLAR ENERGY↗
DOE OSTI2020

Materials Data on BaAgSb by Materials Project

BaSbAg crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional and consists of two silver molecules and one BaSb framework. In the BaSb framework, Ba2+ is bonded to five equivalent Sb3- atoms to form a mixture of edge and corner-sharing BaSb5 trigonal bipyramids. There are three shorter (3.33 Å) and two longer (3.48 Å) Ba–Sb bond lengths. Sb3- is bonded to five equivalent Ba2+ atoms to form a mixture of edge and corner-sharing SbBa5 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SrAgSb by Materials Project

SrSbAg crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional and consists of two silver molecules and one SrSb framework. In the SrSb framework, Sr2+ is bonded to five equivalent Sb3- atoms to form a mixture of corner and edge-sharing SrSb5 trigonal bipyramids. There are three shorter (3.19 Å) and two longer (3.29 Å) Sr–Sb bond lengths. Sb3- is bonded to five equivalent Sr2+ atoms to form a mixture of corner and edge-sharing SbSr5 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Si3Ag3(SnP3)2 by Materials Project

(Ag)3(Sn)2(SiP2)3 crystallizes in the cubic I-43m space group. The structure is three-dimensional and consists of eight 7440-31-5 molecules, twelve silver molecules, and one SiP2 framework. In the SiP2 framework, Si4- is bonded to four equivalent P+0.83+ atoms to form corner-sharing SiP4 tetrahedra. All Si–P bond lengths are 2.28 Å. P+0.83+ is bonded in a distorted water-like geometry to two equivalent Si4- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaNiN by Materials Project

BaNiN is Potassium Silver Cyanide-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to four N3- atoms to form distorted corner-sharing BaN4 tetrahedra. There are a spread of Ba–N bond distances ranging from 2.77–2.84 Å. In the second Ba2+ site, Ba2+ is bonded in a distorted rectangular see-saw-like geometry to four N3- atoms. There are a spread of Ba–N bond distances ranging from 2.81–3.02 Å. There are two inequivalent Ni1+ sites. In the first Ni1+ site, Ni1+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.80 Å) and one longer (1.84 Å) Ni–N bond length. In the second Ni1+ site, Ni1+ is bonded in a linear geometry to two equivalent N3- atoms. Both Ni–N bond lengths are 1.76 Å. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded to four Ba2+ and two equivalent Ni1+ atoms to form a mixture of distorted edge and corner-sharing NBa4Ni2 octahedra. The corner-sharing octahedra tilt angles range from 1–68°. In the second N3- site, N3- is bonded to four Ba2+ and two Ni1+ atoms to form a mixture of distorted edge and corner-sharing NBa4Ni2 octahedra. The corner-sharing octahedra tilt angles range from 0–68°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li7Si2 by Materials Project

Li7Si2 is zeta silver zinc-like structured and crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are eight inequivalent Li sites. In the first Li site, Li is bonded in a 4-coordinate geometry to two equivalent Li and four equivalent Si atoms. Both Li–Li bond lengths are 2.95 Å. All Li–Si bond lengths are 2.57 Å. In the second Li site, Li is bonded in a body-centered cubic geometry to eight Li atoms. There are two shorter (2.36 Å) and six longer (2.65 Å) Li–Li bond lengths. In the third Li site, Li is bonded in a 3-coordinate geometry to five Li and three Si atoms. There are a spread of Li–Li bond distances ranging from 2.38–2.78 Å. There are one shorter (2.53 Å) and two longer (2.66 Å) Li–Si bond lengths. In the fourth Li site, Li is bonded in a 10-coordinate geometry to two Li and four Si atoms. The Li–Li bond length is 2.73 Å. There are a spread of Li–Si bond distances ranging from 2.70–2.91 Å. In the fifth Li site, Li is bonded in a 3-coordinate geometry to seven Li and three Si atoms. There are two shorter (2.70 Å) and two longer (2.88 Å) Li–Li bond lengths. There are one shorter (2.67 Å) and two longer (2.73 Å) Li–Si bond lengths. In the sixth Li site, Li is bonded in a 2-coordinate geometry to three Li and four Si atoms. The Li–Li bond length is 2.49 Å. There are a spread of Li–Si bond distances ranging from 2.65–2.97 Å. In the seventh Li site, Li is bonded in a 2-coordinate geometry to four Li and two equivalent Si atoms. There are one shorter (2.61 Å) and one longer (2.62 Å) Li–Li bond lengths. There are one shorter (2.69 Å) and one longer (2.72 Å) Li–Si bond lengths. In the eighth Li site, Li is bonded in a 12-coordinate geometry to eight Li and four Si atoms. There are a spread of Li–Si bond distances ranging from 2.82–2.96 Å. There are two inequivalent Si sites. In the first Si site, Si is bonded in a 12-coordinate geometry to twelve Li atoms. In the second Si site, Si is bonded in a 11-coordinate geometry to ten Li and one Si atom. The Si–Si bond length is 2.51 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ag25(BiO6)3 by Materials Project

Ag25(BiO6)3 is Potassium Silver Cyanide-derived structured and crystallizes in the trigonal P-3 space group. The structure is three-dimensional. there are six inequivalent Ag1+ sites. In the first Ag1+ site, Ag1+ is bonded in a distorted linear geometry to two O2- atoms. There are one shorter (2.16 Å) and one longer (2.21 Å) Ag–O bond lengths. In the second Ag1+ site, Ag1+ is bonded in a linear geometry to two O2- atoms. There are one shorter (2.14 Å) and one longer (2.15 Å) Ag–O bond lengths. In the third Ag1+ site, Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.13 Å. In the fourth Ag1+ site, Ag1+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. All Ag–O bond lengths are 2.58 Å. In the fifth Ag1+ site, Ag1+ is bonded in a linear geometry to two O2- atoms. Both Ag–O bond lengths are 2.17 Å. In the sixth Ag1+ site, Ag1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ag–O bond lengths are 2.11 Å. There are two inequivalent Bi+3.67+ sites. In the first Bi+3.67+ site, Bi+3.67+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Bi–O bond lengths are 2.20 Å. In the second Bi+3.67+ site, Bi+3.67+ is bonded in an octahedral geometry to six O2- atoms. There are three shorter (2.27 Å) and three longer (2.46 Å) Bi–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Ag1+ and one Bi+3.67+ atom. In the second O2- site, O2- is bonded to three Ag1+ and one Bi+3.67+ atom to form distorted corner-sharing OAg3Bi tetrahedra. In the third O2- site, O2- is bonded to three Ag1+ and one Bi+3.67+ atom to form corner-sharing OAg3Bi tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCN2 by Materials Project

BaCN2 is Potassium Silver Cyanide-derived structured and crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Ba2+ is bonded to six equivalent N3- atoms to form a mixture of distorted edge and corner-sharing BaN6 pentagonal pyramids. There are a spread of Ba–N bond distances ranging from 2.78–2.91 Å. C4+ is bonded in a linear geometry to two equivalent N3- atoms. Both C–N bond lengths are 1.24 Å. N3- is bonded in a 1-coordinate geometry to three equivalent Ba2+ and one C4+ atom.

36 MATERIALS SCIENCE↗