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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 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

3D Hybrid Plasmonic Framework with Au Nanopillars Embedded in Nitride Multilayers Integrated on Si

Integration of nanoscale photonic and plasmonic components on Si substrates is a critical step toward Si-based integrated nanophotonic devices. Herein, a set of unique complex 3D metamaterials with intercalated nanolayered and nanopillar structures with tunable plasmonic and optical properties on Si substrates is designed. More specifically, the 3D metamaterials combine metal (Au) nanopillars and alternating metal-nitride (Au-TiN and Au-TaN) nanolayers, epitaxially grown on Si substrates. The ultrafine Au nanopillars ( d ≈ 3 nm) continuously grow throughout all the nanolayers with high epitaxial quality. Novel optical properties, such as highly anisotropic optical property, high absorbance covering the entire visible spectrum regime, and hyperbolic property in the visible regime, are demonstrated. Furthermore, a waveguide based on a silicon nitride (Si 3 N 4 ) ridge with a multilayer structure is successfully fabricated. The demonstration of 3D nanoscale metamaterial design integrated on Si opens up a new route toward tunable metamaterials nanostructure designs with versatile material selection for various optical components in Si integrated photonics.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Light‐Gated Synthetic Protocells for Plasmon‐Enhanced Chemiosmotic Gradient Generation and ATP Synthesis

Abstract Herein, we present a light‐gated protocell model made of plasmonic colloidal capsules (CCs) assembled with bacteriorhodopsin for converting solar energy into electrochemical gradients to drive the synthesis of energy‐storage molecules. This synthetic protocell incorporated an important intrinsic property of noble metal colloidal particles, namely, plasmonic resonance. In particular, the near‐field coupling between adjacent metal nanoparticles gave rise to strongly localized electric fields and resulted in a broad absorption in the whole visible spectra, which in turn promoted the flux of photons to bacteriorhodopsin and accelerated the proton pumping kinetics. The cell‐like potential of this design was further demonstrated by leveraging the outward pumped protons as “chemical signals” for triggering ATP biosynthesis in a coexistent synthetic protocell population. Hereby, we lay the ground work for the engineering of colloidal supraparticle‐based synthetic protocells with higher‐order functionalities.

Chen, Zhaowei↗
DOE OSTI2019

Comparative analysis of silicon and black phosphorous as an add-layer in nanomaterial based plasmonic sensor

In the proposed article silicon and black phosphorous as an add-layer above the plasmonic metal in nanomaterial (graphene and MoS{sub 2}) based plasmonic sensor are compared. The reflectance curves are obtained for different thickness of silicon and black phosphorous by using transfer matrix method. The performance defining parameters i.e. shift in resonance angle, beam width of reflectance curve, and minimum reflectance intensity for a minute change of 0.005 in refractive index of sensing medium at the optimized thickness 5 nm of silicon and black-phosphorous, and conventional are (13.86, 10.96, 2.415), (4.956, 3.817, 1.419), and (0.012, 0.002, 0.002) respectively. Further, the addition of nanomaterials increases these parameters and generally follows the order MoS{sub 2}-graphene > MoS{sub 2} > graphene. Furthermore, transverse-magnetic electric field shows that nanomaterial covered silicon have higher penetration depth than the nanomaterial covered black-phosphorous. The analysis shows that nanomaterial covered silicon can replace nanomaterial covered black-phosphorous in terms of higher sensitivity and penetration depth.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Design of all-optical XOR and XNOR logic gates based on Fano resonance in plasmonic ring resonators

In this paper, compact all-optical XOR and XNOR gates based on different configurations of metal–insulator–metal plasmonic ring resonators (PRRs) have been proposed. Square and octagon-shaped rings have been used in this case. The logic gates have been simulated using the two-dimensional finite-difference time-domain numerical method, with a conventional perfectly matched layer as the absorbing boundary condition of the area under simulation. The phenomenon of Fano resonance is employed by the proposed gates to excite ON/OFF states. As a result, a large value of contrast ratio (C.R.) is obtained. The results show that the values of C.R. of XNOR and XOR gates for square-shaped PRR are 22.66 and 22.9 dB, respectively and the values of C.R. of XNOR and XOR gates for octagon-shaped PRR are 23.01 and 23.52 dB, respectively. Also, it is shown that the octagon-shaped gates have higher transmission ratios than other proposed configurations. The proposed optical logic gates can be used as key components in optical communications and for designing compact plasmonic devices.

42 ENGINEERING↗
DOE OSTI2019

Nanoscale plasmonic detector of wave intensity difference and uni-directional waveguide

In this paper, a new nanoscale plasmonic differential detector of wave intensities is proposed. This structure can be useful for calibration applications and for finding out if a wave intensity is high enough to pass a threshold level or not. Next, a nanoscale plasmonic uni-directional waveguide is presented. The distinction of this waveguide with similar cases is that the one-way wave-guiding is provided by adding a properly located controlling source, without employing any non-reciprocal material. This feature can be used in many applications that only uni-directional wave propagation is desirable. Both structures have been designed in metal–insulator–metal structure including cavity resonators. The operations are based on the coupling of the wave from input waveguides to the cavity resonators and decoupling to output waveguides in the cavity resonance wavelengths. The simulation results of performance of the structures, as elements applicable to photonic integrated circuits, have been obtained using the numerical method of the finite difference time domain.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Bio-compatible and highly sensitive two-dimensional plasmonic sensor

We propose a novel bio-compatible two dimensional plasmonic sensor with array of ring and the hole structure on an optically thick gold film for biochemical sensing. We use finite-difference time-domain simulation for design and calculation of sensitivity in the near-infrared region. The bio-compatible and cheap plasmonic glycerol sensor with high sensitivity by interferometer style as a motif in the sensor’s structure. The proposed sensor can be applied as highly sensitivity sensor with a good linear response under different glycerol concentrations.

42 ENGINEERING↗
DOE OSTI2019

Fano resonances based on plasmonic square resonator with high figure of merits and its application in glucose concentrations sensing

A compact plasmonic structure is proposed employing symmetrical metal–insulator-metal (MIM) waveguides coupled to the square resonator for nano-sensing applications, especially for water glucose sensing. Finite difference time domain method is chosen to derivate the output characteristics and magnetic-field distributions. Outcomes illustrate the Fano resonance in the output characteristics can be simply managed by varying the inner and outer lengths and the refractive index of the square cavity. Also, between Fano resonance wavelength and resonator length, a linear behavior exists. These features suggest that physical parameters provide flexibility to propose the structure. Our plasmonic device produces a sensitivity and figure of merit of about 6400 nm/RIU and 1 × 10{sup 4}, respectively. By utilizing the mathematical model for water refractive index, we aim to develop a sensor structure to detect the glucose concentration in water. This designed sensor may discover significant applications in future nanosensing domain.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Plasmonic hybrid core-shell (HyCoS) AgPt NP template hybridized with GQDs for SERS enhancement of 4-MBA and BT

Surface-enhanced Raman spectroscopy (SERS) is an attractive vibrational spectroscopic technique that can enable a non-destructive and ultra-sensitive detection down to the single-molecule level. Herein, a novel hybrid SERS platform is developed based on hybrid core-shell (HyCoS) AgPt nanoparticles (NPs) and graphene quantum dots (GQDs) for the enhancement of Raman vibration of 4-mercaptobenzoic acid (4-MBA) and benzenethiol (BT). The unique design of HyCoS AgPt NPs induces strong electromagnetic mechanism (EM) enhancement through the amplification of electromagnetic fields by the excitation of high-density surface plasmons and hot spots. Superior localized surface plasmon resonance (LSPR) is generated by the AgPt core-shell and background Ag NP coupling, which is systematically investigated by the optical properties and FDTD simulations. The background Ag NPs can further increase the coverage of metallic NPs, leading to higher-density hot spots and enhanced SERS response. At the same time, GQDs can provide plentiful accessible edges for the charge transfer to the HOMO and LUMO of 4-MBA and BT based on the chemical mechanism (CM) enhancement. The mixing approach of GQDs and target molecules on the HyCoS AgPt NPs can significantly amplify the Raman signals via the strong adsorption of probe molecules by the π – π interaction. The enhancement factors of proposed SERS platform can reach ~107 and ~105 for the 4-MBA and BT respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Synthesis, characterization and evaluation of the photocatalytic performance of Ag-CdMoO{sub 4} solar light driven plasmonic photocatalyst

Graphical abstract: - Highlights: • Ag-CdMoO{sub 4} solar light driven photocatalyst was successfully synthesized. • Photocatalyst exhibited strong absorption in the visible region. • Photocatalytic activity was significantly enhanced. • Enhanced activity was caused by the SPR effect induced by Ag nanoparticles. - Abstract: Ag-CdMoO{sub 4} plasmonic photocatalyst was synthesized in ethanol/water mixture by photo assisted co-precipitation method at room temperature. As synthesized powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analyzer. Photocatalytic activity was evaluated by performing the degradation experiment over methylene blue (MB) and indigo carmine (IC) as model dyes under simulated solar light irradiation. The results revealed that the Ag-CdMoO{sub 4} showed the higher photocatalytic performance as compared to CdMoO{sub 4} nanoparticles. Dispersion of Ag nanoparticles over the surface of CdMoO{sub 4} nanoparticles causes the surface plasmon resonance (SPR) and enhances the broad absorption in the entire visible region of the solar spectrum. Hence, dispersion of Ag nanoparticles over CdMoO{sub 4} nanoparticles could be the better alternative to enhance the absorption of visible light by scheelite crystal family for effective photocatalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2015

A facile strategy to fabricate plasmonic Cu modified TiO{sub 2} nano-flower films for photocatalytic reduction of CO{sub 2} to methanol

Graphical abstract: Photoreduction of CO{sub 2} to CH{sub 3}OH over plasmonic Cu/TiO{sub 2} film. - Highlights: • Cu nanoparticles modified TiO{sub 2} nano-flower film was prepared by a facile strategy. • Cu nanoparticles can enhance the light absorption and the Raman scattering of TiO{sub 2}. • Cu nanoparticles can effectively restrain the recombination of the charge carriers. • A synergistic mechanism is proposed for photocatalytic reduction of CO{sub 2} on Cu/TiO{sub 2} film. - Abstract: Cu nanoparticles (NPs) deposited TiO{sub 2} nano-flower films were fabricated using a combination of a hydrothermal method and a microwave-assisted reduction process. The investigations indicated that Cu NPs and TiO{sub 2} film both exhibit visible light harvesting properties based on localized surface plasmon resonance (LSPR) of Cu NPs and unique nanostructures of TiO{sub 2} film. Fluorescence quenching was observed because the recombination of charge carriers was effectively suppressed by Cu NPs deposition. The experimental results indicate that Cu/TiO{sub 2} films exhibit better activity for the photocatalytic reduction of CO{sub 2} due to the charge transfer property and LSPR effect of Cu NPs. The CH{sub 3}OH production rate reached 1.8 μmol cm{sup −2} h{sup −1} (energy efficiency was 0.8%) over 0.5 Cu/TiO{sub 2} film under UV and visible light irradiation, which was 6.0 times higher than that observed over pure TiO{sub 2} film. In addition, a tentative photocatalytic mechanism is proposed to understand the experimental results over the Cu modified TiO{sub 2} nano-flower films.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

Plasmon-enhanced broad-band quantum-cutting of NaBaPO{sub 4}:Eu{sup 2+},Yb{sup 3+} phosphor decorated with Ag nano-particles

Highlights: • High quantum-cutting (QC) efficiency as 197.4% was obtained in NaBaPO{sub 4}:Eu{sup 2+},Yb{sup 3+}. • Strong and broad excitation band derived from Eu{sup 2+} was detected and analyzed. • Plasmon enhancement of broad-band QC emission was reported for the first time. - Abstract: The NaBaPO{sub 4}:Eu{sup 2+},Yb{sup 3+} quantum-cutting (QC) phosphors were prepared by the solid-state reaction. We confirm the luminescence of Yb{sup 3+} is mainly derived from QC rather than common down-conversion. The QC efficiency η{sub QE} calculated from the luminescence decay curves reached a maximum as high as 197.4%. Furthermore, the QC emission was enhanced by decorating with quasi-spherical and uniform (∼100 nm) Ag nano-particles, due to localized surface plasmon resonance. The enhancement factor reached a maximum as 1.2337.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Integration of Ag2WO4 and AgBr with TiO2 to fabricate ternary nanocomposites: Novel plasmonic photocatalysts with remarkable activity under visible light

Highlights: • Novel TiO{sub 2}/Ag{sub 2}WO{sub 4}/AgBr nanocomposites as efficient photocatalysts are reported. • The TiO{sub 2}/Ag{sub 2}WO{sub 4}/AgBr (15%) nanocomposite exhibited the highest activity. • Activity was 50.6-folds greater than TiO{sub 2} in RhB degradation under visible light. • The enhanced activity was attributed to n-n heterojunctions and plasmonic effect. - Abstract: Novel and highly efficient visible-light-driven TiO{sub 2}/Ag{sub 2}WO{sub 4}/AgBr plasmonic photocatalysts were fabricated by a simple one-pot strategy and they were characterized using XRD, EDX, FESEM, TEM, HRTEM, UV–vis DRS, FT–IR, and PL instruments. The TiO{sub 2}/Ag{sub 2}WO{sub 4}/AgBr nanocomposites exhibited higher photocatalytic performance under visible light for RhB, fuchsine, and MO degradations compared with the pure TiO{sub 2} and binary TiO{sub 2}/Ag{sub 2}WO{sub 4} and TiO{sub 2}/AgBr nanocomposites. The optimum photocatalytic activity of the TiO{sub 2}/Ag{sub 2}WO{sub 4}/AgBr (15%) nanocomposite is greater than those of the TiO{sub 2}, TiO{sub 2}/Ag{sub 2}WO{sub 4} (10%), and TiO{sub 2}/AgBr (15%) photocatalysts towards the degradation of RhB by a factor of almost 50.6, 22.6, and 5.1, respectively. The degradation reaction was also examined through trapping experiments and a mechanism for generation of the e{sup −}/h{sup +} pairs under visible light and promotion spatial separation of the charges through tandem n-n heterojunctions was proposed. We anticipate that the procedure used in this paper can provide a good protocol to design efficient visible-light-driven photocatalysts using TiO{sub 2} for environmental applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Aqueous Synthesis of Concave Rh Nanotetrahedra with Defect-Rich Surfaces: Insights into Growth-, Defect-, and Plasmon-Enhanced Catalytic Energy Conversion

The control of morphology in the synthesis of Rh nanocrystals can be used to precisely tailor the electronic surface structure; this in turn directly influences their performance in catalysis applications. Many works have brought attention to the development of Rh nanostructures with low-index surfaces, but limited effort has been devoted to the study of high-index and surface defect-enriched nanocrystals as they are not favored by thermodynamics because of the involvement of high-energy surfaces and increased surface-to-volume ratios. Here, we demonstrate an aqueous synthesis of concave Rh nanotetrahedra (CTDs) serving as efficient catalysts for energy conversion reactions. CTDs are surface defect-rich structures that form through a slow growth rate and follow the four-step model of metallic nanoparticle growth. Via the tuning of the surfactant concentration, the morphology of Rh CTDs evolved into highly excavated nanotetrahedra (HETDs) and twinned nanoparticles (TWs). Unlike the CTD surfaces with abundant adatoms and vacancies, HETDs and TWs have more regular surfaces with layered terraces. Each nanocrystal type was evaluated for methanol electrooxidation and hydrogen evolution from hydrolysis of ammonia borane, and the CTDs significantly showed the best catalytic performance because of defect enrichment, which benefits the surface reactivity of adsorbates. In addition, both CTDs and HETDs have strong absorption near the visible light region (382 and 396 nm), for which they show plasmon-enhanced performance in photocatalytic hydrogen evolution under visible light illumination. CTDs are more photoactive than HETDs, likely because of more pronounced localized surface plasmon resonance hot spots. Lastly, this facile aqueous synthesis of large-surface-area, defect-rich Rh nanotetrahedra is exciting for the fields of nanosynthesis and catalysis.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A Metal-on-Metal Growth Approach to Metal–Metal Oxide Core–Shell Nanostructures with Plasmonic Properties

Hybrid core–shell nanoparticles integrate the material properties from individual components; however, the synthesis of core–shell nanoparticles with dissimilar materials remains challenging. Herein, we applied a metal-on-metal thin film growth approach to control the conformal deposition of non-precious metal shells on the Cu-based metal cores to form core–shell structures of metal–metal oxide hybrids (M–M'O x , where M = AuCu 3 or Cu, M' = Fe, Mn, and Ni). The deposition kinetics were controlled by a temperature-regulated thermal decomposition of zerovalent transition metal complexes. It is predicted that the conformal deposition can be promoted by keeping the initial deposition temperature close to the thermal decomposition temperature of the zerovalent precursors. The mechanisms of strain reduction and interdiffusion facilitate conformal deposition over island growth in the synthesis with slow reaction kinetics. This study provides insightful guidance to metal-on-metal growth in solution at the nanoscale and thus the seed-mediated approach to hybrid core–shell structures. The optical properties of these metal–metal oxide hybrids were investigated experimentally and interpreted by theoretical simulations. Despite damping effects, the plasmonic properties of these Cu-based core-metal oxide shell structures may have the potential to enable plasmon-enhanced applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Formation of Linear Plasmonic Heterotrimers Using Nanoparticle Docking to DNA Origami Cages

The fabrication of complex assemblies with interesting collective properties from plasmonic nanoparticles (NPs) is often challenging. While DNA-directed self-assembly has emerged as one of the most promising approaches to forming such complex assemblies, the resulting structures tend to have large variability in gap sizes and shapes, as the DNA strands used to organize these particles are flexible, and the polydispersity of the NPs leads to variability in these critical structural features. Here, we use a new strategy termed docking to DNA origami cages (D-DOC) to organize spherical NPs into a linear heterotrimer with a precisely defined geometrical arrangement. Instead of binding NPs to the exterior of the DNA templates, D-DOC binds the NPs to either the interior or the opening of a 3D cage, which significantly reduces the variability of critical structural features by incorporating multiple diametrically arranged capture strands to tether NPs. Additionally, such a spatial arrangement of the capture strand can work synergistically with shape complementarity to achieve tighter confinement. To assemble NPs via D-DOC, we developed a multistep assembly process that first encapsulates an NP inside a cage and then binds two other NPs to the openings. Microscopic characterization shows low variability in the bond angles and gap sizes. Both UV–vis absorption and surface-enhanced Raman scattering (SERS) measurements showed strong plasmonic coupling that aligned with predictions by electrodynamic simulations, further confirming the precision of the assembly. These results suggest D-DOC could open new opportunities in biomolecular sensing, SERS and fluorescence spectroscopies, and energy harvesting through the self-assembly of NPs into more complex 3D assemblies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Tip-Enhanced Raman Nanographs of Plasmonic Silver Nanoparticles

Tip-Enhanced Raman Scattering (TERS) from plasmonic silver nanoparticles traces spatial variations in optical fields defined by the interaction of the plasmonic probe with nanoscale topographic features that are characteristic of crystalline particles. This is demonstrated through correlated atomic force microscopy (AFM)-TERS imaging of ~100 nm silver nanoparticles coated with 4-mercaptobenzonitrile (MBN) molecules. In effect, the recorded spectral images are sensitive to the 3D topographic makeup of the particle and broadcast local optical fields that vary over a few nanometers length scale.

Bhattarai, Ashish↗
DOE OSTI2020

The Prevalence of Anions at Plasmonic Nanojunctions: A Closer Look at P-Nitrothiophenol

We revisit the reductive coupling of p-nitrothiophenol (NTP) to form dimercaptoazobenzene (DMAB), herein monitored through gap-mode tip-enhanced Raman spectroscopy (TERS) and nano-imaging. We employ a plasmonic Au probe (100 nm diameter at its apex) illuminated with a 633 nm laser source (50 ?W/?m2 at the sample position) to image a NTP-coated faceted silver nanoparticle (~70 nm diameter). A detailed analysis of the recorded spectra reveals that anionic NTP species contribute to the recorded spectral images, in addition to the more thoroughly described DMAB product. Notably, the signatures of the anions are more pronounced than those of the DMAB product under our present experimental conditions. Our results thus demonstrate that anions and their spectral signatures must be considered in the analysis of plasmon-enhanced spectra and images.

Wang, Chih-Feng↗
DOE OSTI2020

Activation and Assembly of Plasmonic-Magnetic Nanosurfactants for Encapsulation and Triggered Release

Multifunctional surfactants hold great potentials in catalysis, separation, and biomedicine. Highly active plasmonic-magnetic nanosurfactants are developed through a novel acid activation treatment of Au–Fe 3 O 4 dumbbell nanocrystals. The activation step significantly boosts nanosurfactant surface energy and enables the strong adsorption at interfaces, which reduces the interfacial energy one order of magnitude. Mediated through the adsorption at the emulsion interfaces, the nanosurfactants are further constructed into free-standing hierarchical structures, including capsules, inverse capsules, and two-dimensional sheets. The nanosurfactant orientation and assembly structures follow the same packing parameter principles of surfactant molecules. Furthermore, nanosurfactants demonstrate the capability to disperse and encapsulate homogeneous nanoparticles and small molecules without adding any molecular surfactants. The assembled structures are responsive to external magnetic field, and triggered release is achieved using an infrared laser by taking advantage of the enhanced surface plasmon resonance of nanosurfactant assemblies. Finally, solvent and pH changes are also utilized to achieve the cargo release.

77 NANOSCIENCE AND NANOTECHNOLOGY↗