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DDC: 530 × DDC: 670 × Publisher: Weinheim : Wiley-VCH ×

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Now showing 1 - 10 of 15
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    Actively Tunable Collective Localized Surface Plasmons by Responsive Hydrogel Membrane
    (Weinheim : Wiley-VCH, 2019) Quilis, Nestor Gisbert; van Dongen, Marcel; Venugopalan, Priyamvada; Kotlarek, Daria; Petri, Christian; Cencerrado, Alberto Moreno; Stanescu, Sorin; Herrera, Jose Luis Toca; Jonas, Ulrich; Möller, Martin; Mourran, Ahmed; Dostalek, Jakub
    Collective (lattice) localized surface plasmons (cLSP) with actively tunable and extremely narrow spectral characteristics are reported. They are supported by periodic arrays of gold nanoparticles attached to a stimuli-responsive hydrogel membrane, which can on demand swell and collapse to reversibly modulate arrays period and surrounding refractive index. In addition, it features a refractive index-symmetrical geometry that promotes the generation of cLSPs and leads to strong suppression of radiative losses, narrowing the spectral width of the resonance, and increasing of the electromagnetic field intensity. Narrowing of the cLSP spectral band down to 13 nm and its reversible shifting by up to 151 nm is observed in the near infrared part of the spectrum by varying temperature and by solvent exchange for systems with a poly(N-isopropylacrylamide)-based hydrogel membrane that is allowed to reversibly swell and collapse in either one or in three dimensions. The reported structures with embedded periodic gold nanoparticle arrays are particularly attractive for biosensing applications as the open hydrogel structure can be efficiently post-modified with functional moieties, such as specific ligands, and since biomolecules can rapidly diffuse through swollen polymer networks. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Photoluminescence Mapping over Laser Pulse Fluence and Repetition Rate as a Fingerprint of Charge and Defect Dynamics in Perovskites
    (Weinheim : Wiley-VCH, 2023) Rao, Shraddha M.; Kiligaridis, Alexander; Yangui, Aymen; An, Qingzhi; Vaynzof, Yana; Scheblykin, Ivan G.
    Defects in metal halide perovskites (MHP) are photosensitive, making the observer effect unavoidable when laser spectroscopy methods are applied. Photoluminescence (PL) bleaching and enhancement under light soaking and recovery in dark are examples of the transient phenomena that are consequent to the creation and healing of defects. Depending on the initial sample composition, environment, and other factors, the defect nature and evolution can strongly vary, making spectroscopic data analysis prone to misinterpretations. Herein, the use of an automatically acquired dependence of PL quantum yield (PLQY) on the laser pulse repetition rate and pulse fluence as a unique fingerprint of both charge carrier dynamics and defect evolution is demonstrated. A simple visual comparison of such fingerprints allows for assessment of similarities and differences between MHP samples. The study illustrates this by examining methylammonium lead triiodide (MAPbI3) films with altered stoichiometry that just after preparation showed very pronounced defect dynamics at time scale from milliseconds to seconds, clearly distorting the PLQY fingerprint. Upon weeks of storage, the sample fingerprints evolve toward the standard stoichiometric MAPbI3 in terms of both charge carrier dynamics and defect stability. Automatic PLQY mapping can be used as a universal method for assessment of perovskite sample quality.
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    Tunable Circular Dichroism by Photoluminescent Moiré Gratings
    (Weinheim : Wiley-VCH, 2020) Aftenieva, Olha; Schnepf, Max; Mehlhorn, Börge; König, Tobias A.F.
    In nanophotonics, there is a current demand for ultrathin, flexible nanostructures that are simultaneously easily tunable, demonstrate a high contrast, and have a strong response in photoluminescent polarization. In this work, the template-assisted self-assembly of water-dispersed colloidal core–shell quantum dots into 1D light-emitting sub-micrometer gratings on a flexible substrate is demonstrated. Combining such structures with a light-absorbing metallic counterpart by simple stacking at various angles results in a tunable Moiré pattern with strong lateral contrast. Furthermore, a combination with an identical emitter-based grating leads to a chiroptical effect with a remarkably high degree of polarization of 0.72. Such a structure demonstrates direct circular polarized photoluminescence, for the first time, without a need for an additional chiral template as an intermediary. The suggested approach allows for reproducible, large-area manufacturing at reasonable costs and is of potential use for chiroptical sensors, photonic circuit applications, or preventing counterfeit. © 2020 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
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    Spectrometer‐free Optical Hydrogen Sensing Based on Fano‐like Spatial Distribution of Transmission in a Metal−Insulator−Metal Plasmonic Doppler Grating
    (Weinheim : Wiley-VCH, 2021) Chen, Yi‐Ju; Lin, Fan‐Cheng; Singh, Ankit Kumar; Ouyang, Lei; Huang, Jer‐Shing
    Optical nanosensors are promising for hydrogen sensing because they are small, free from spark generation, and feasible for remote optical readout. Conventional optical nanosensors require broadband excitation and spectrometers, rendering the devices bulky and complex. An alternative is spatial intensity-based optical sensing, which only requires an imaging system and a smartly designed platform to report the spatial distribution of analytical optical signals. Here, a spatial intensity-based hydrogen sensing platform is presented based on Fano-like spatial distribution of the transmission in a Pd-Al2O3-Au metal-insulator-metal plasmonic Doppler grating (MIM-PDG). The MIM-PDG manifests the Fano resonance as an asymmetric spatial transmission intensity profile. The absorption of hydrogen changes the spatial Fano-like transmission profiles, which can be analyzed with a “spatial” Fano resonance model and the extracted Fano resonance parameters can be used to establish analytical calibration lines. While gratings sensitive to hydrogen absorption are suitable for hydrogen sensing, hydrogen insensitive gratings are also found, which provide an unperturbed reference signal and may find applications in nanophotonic devices that require a stable optical response under fluctuating hydrogen atmosphere. The MIM-PDG platform is a spectrometer-free and intensity-based optical sensor that requires only an imaging system, making it promising for cellphone-based optical sensing applications. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH.
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    Tailoring Plasmonics of Au@Ag Nanoparticles by Silica Encapsulation
    (Weinheim : Wiley-VCH, 2021) Schultz, Johannes; Kirner, Felizitas; Potapov, Pavel; Büchner, Bernd; Lubk, Axel; Sturm, Elena V.
    Hybrid metallic nanoparticles (NPs) encapsulated in oxide shells are currently intensely studied for plasmonic applications in sensing, medicine, catalysis, and photovoltaics. Here, a method for the synthesis of Au@Ag@SiO2 cubes with a uniform silica shell of variable and adjustable thickness in the nanometer range is introduced and their excellent, highly reproducible, and tunable optical response is demonstrated. Varying the silica shell thickness, the excitation energies of the single NP plasmon modes can be tuned in a broad spectral range between 2.55 and 3.25 eV. Most importantly, a strong coherent coupling of the surface plasmons is revealed at the silver–silica interface with Mie resonances at the silica–vacuum interface leading to a significant field enhancement at the encapsulated NP surface in the range of 100% at shell thicknesses t ≃ 20 nm. Consequently, the synthesis method and the field enhancement open pathways to a widespread use of silver NPs in plasmonic applications including photonic crystals and may be transferred to other non-precious metals. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
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    Colloidal Self-Assembly Concepts for Plasmonic Metasurfaces
    (Weinheim : Wiley-VCH, 2019) Mayer, Martin; Schnepf, Max J.; König, Tobias A.F.; Fery, Andreas
    Metallic nanostructures exhibit strong interactions with electromagnetic radiation, known as the localized surface plasmon resonance. In recent years, there is significant interest and growth in the area of coupled metallic nanostructures. In such assemblies, short- and long-range coupling effects can be tailored and emergent properties, e.g., metamaterial effects, can be realized. The term “plasmonic metasurfaces” is used for this novel class of assemblies deposited on planar surfaces. Herein, the focus is on plasmonic metasurfaces formed from colloidal particles. These are formed by self-assembly and can meet the demands of low-cost manufacturing of large-area, flexible, and ultrathin devices. The advances in high optical quality of the colloidal building blocks and methods for controlling their self-assembly on surfaces will lead to novel functional devices for dynamic light modulators, pulse sharpening, subwavelength imaging, sensing, and quantum devices. This progress report focuses on predicting optical properties of single colloidal building blocks and their assemblies, wet-chemical synthesis, and directed self-assembly of colloidal particles. The report concludes with a discussion of the perspectives toward expanding the colloidal plasmonic metasurfaces concept by integrating them with quantum emitters (gain materials) or mechanically responsive structures. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    The Potential of Combining Thermal Scanning Probes and Phase-Change Materials for Tunable Metasurfaces
    (Weinheim : Wiley-VCH, 2020) Michel, Ann-Katrin U.; Meyer, Sebastian; Essing, Nicolas; Lassaline, Nolan; Lightner, Carin R.; Bisig, Samuel; Norris, David J.; Chigrin, Dmitry N.
    Metasurfaces allow for the spatiotemporal variation of amplitude, phase, and polarization of optical wavefronts. Implementation of active tunability of metasurfaces promises compact flat optics capable of reconfigurable wavefront shaping. Phase-change materials (PCMs) are a prominent material class enabling reconfigurable metasurfaces due to their large refractive index change upon structural transition. However, commonly employed laser-induced switching of PCMs limits the achievable feature sizes and restricts device miniaturization. Thermal scanning-probe-induced local switching of the PCM germanium telluride is proposed to realize near-infrared metasurfaces with feature sizes far below what is achievable with diffraction-limited optical switching. The design is based on a planar multilayer and does not require fabrication of protruding resonators as commonly applied in the literature. Instead, it is numerically demonstrated that a broad-band tuning of perfect absorption can be realized by the localized tip-induced crystallization of the PCM. The spectral response of the metasurface is explained using resonance mode analysis and numerical simulations. To facilitate experimental realization, a theoretical description of the tip-induced crystallization employing multiphysics simulations is provided to demonstrate the great potential for fabricating compact reconfigurable metasurfaces. The concept can be applied not only for plasmonic sensing and spatial frequency filtering, but also be transferred to all-dielectric metasurfaces. © 2020 Wiley-VCH GmbH
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    Exploiting Combinatorics to Investigate Plasmonic Properties in Heterogeneous Ag-Au Nanosphere Chain Assemblies
    (Weinheim : Wiley-VCH, 2021) Schletz, Daniel; Schultz, Johannes; Potapov, Pavel L.; Steiner, Anja Maria; Krehl, Jonas; König, Tobias A.F.; Mayer, Martin; Lubk, Axel; Fery, Andreas
    Chains of coupled metallic nanoparticles are of special interest for plasmonic applications because they can sustain highly dispersive plasmon bands, allowing strong ballistic plasmon wave transport. Whereas early studies focused on homogeneous particle chains exhibiting only one dominant band, heterogeneous assemblies consisting of different nanoparticle species came into the spotlight recently. Their increased configuration space principally allows engineering multiple bands, bandgaps, or topological states. Simultaneously, the challenge of the precise arrangement of nanoparticles, including their distances and geometric patterns, as well as the precise characterization of the plasmonics in these systems, persists. Here, the surface plasmon resonances in heterogeneous Ag-Au nanoparticle chains are reported. Wrinkled templates are used for directed self-assembly of monodisperse gold and silver nanospheres as chains, which allows assembling statistical combinations of more than 109 particles. To reveal the spatial and spectral distribution of the plasmonic response, state-of-the-art scanning transmission electron microscopy coupled with electron energy loss spectroscopy accompanied by boundary element simulations is used. A variety of modes in the heterogeneous chains are found, ranging from localized surface plasmon modes occurring in single gold or silver spheres, respectively, to modes that result from the hybridization of the single particles. This approach opens a novel avenue toward combinatorial studies of plasmonic properties in heterosystems. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
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    Emission Manipulation by DNA Origami‐Assisted Plasmonic Nanoantennas
    (Weinheim : Wiley-VCH, 2021) Yeşilyurt, Ayşe Tuğça Mina; Huang, Jer‐Shing
    Plasmonic nanoantennas mediate far and near optical fields and confine the light to subwavelength dimensions. The spatial organization of nanoantenna elements is critical as it affects the interelement coupling and determines the resultant antenna mode. To couple quantum emitters to optical antennas, high precision on the order of a few nm with respect to the antenna is necessary. As an emerging nanofabrication technique, DNA origami has proven itself to be a robust nanobreadboard to obtain sub-5 nm positioning precision for a diverse range of materials. Eliminating the need for expensive state-of-the-art top-down fabrication facilities, DNA origami enables cost-efficient implementation of nanoscale architectures, including novel nanoantennas. The ability of DNA origami to deterministically position single quantum emitters into nanoscale hotspots further boosts the efficiency of light–matter interaction controlled via optical antennas. This review recapitulates the recent progress in plasmonic nanoantennas assisted by DNA origami and focuses on their various configurations. How those nanoantennas act on the emission and absorption properties of quantum emitters positioned in the hotspots is explicitly discussed. In the end, open challenges are outlined and future possibilities lying ahead are pointed out for this powerful triad of biotechnology, nanooptics, and photophysics. © 2021 The Authors. Advanced Optical Materials published by Wiley-VCH GmbH
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    Remarkable Mechanochromism in Blends of a π-Conjugated Polymer P3TEOT: The Role of Conformational Transitions and Aggregation
    (Weinheim : Wiley-VCH, 2020) Zessin, Johanna; Schnepf, Max; Oertel, Ulrich; Beryozkina, Tetyana; König, Tobias A.F.; Fery, Andreas; Mertig, Michael; Kiriy, Anton
    A novel mechanism for well-pronounced mechanochromism in blends of a π-conjugated polymer based on reversible conformational transitions of a chromophore rather than caused by its aggregation state, is exemplified. Particularly, a strong stretching-induced bathochromic shift of the light absorption, or hypsochromic shift of the emission, is found in blends of the water-soluble poly(3-tri(ethylene glycol)) (P3TEOT) embedded into the matrix of thermoplastic polyvinyl alcohol. This counterintuitive phenomenon is explained in terms of the concentration dependency of the P3TEOT's aggregation state, which in turn results in different molecular conformations and optical properties. A molecular flexibility, provided by low glass transition temperature of P3TEOT, and the fact that P3TEOT adopts an intermediate, moderately planar conformation in the solid state, are responsible for the unusual complex mechanochromic behavior. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim