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206 results on '"König, Tobias A. F."'

2. Silver particles with rhombicuboctahedral shape and effectively isotropic interactions with light

Author

Steiner, Anja Maria, Mayer, Martin, Schletz, Daniel, Wolf, Daniel, Formanek, Petr, Hübner, René, Dulle, Martin, Förster, Stephan, König, Tobias A. F., and Fery, Andreas

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

Truly spherical silver nanoparticles are of great importance for fundamental studies including plasmonic applications, but the direct synthesis in aqueous media is not feasible. Using the commonly employed copper-based etching processes, isotropicplasmonic response can be achieved by etching well-defined silver nanocubes. Whilst spherical like shape is typically prevailing in such processes, we established that there is a preferential growth towards silver rhombicuboctahedra (AgRCOs), which is thethermodynamically most stable product of this synthesis. The rhombicuboctahedral morphology is further evidenced by comprehensive characterization with small-angle X-ray scattering in combination with TEM tomographyand high resolution TEM. Wealso elucidate the complete reaction mechanism based on UV-Vis kinetic studies, and the postulated mechanism can also be extended to all copper-based etching processes.

Published
2019
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3. Direct Observation of Plasmon Band Formation and Delocalization in Quasi-Infinite Nanoparticle Chains

Author

Mayer, Martin, Potapov, Pavel L., Pohl, Darius, Steiner, Anja Maria, Schultz, Johannes, Rellinghaus, Bernd, Lubk, Axel, König, Tobias A. F., and Fery, Andreas

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Chains of metallic nanoparticles sustain strongly confined surface plasmons with relatively low dielectric losses. To exploit these properties in applications,such as waveguides, the fabrication of long chains of low disorder and a thorough understanding of the plasmon-mode properties, such as dispersion relations, are indispensable. Here, we use a wrinkled template for directed self-assembly to assemble chains of gold nanoparticles. With this up-scalable method, chain lengths from two particles (140 nm) to 20 particles (1500 nm) and beyond can be fabricated. Electron energy-loss spectroscopy supported by boundary element simulations, finite-difference time-domain, and a simplified dipole coupling model reveal the evolution of a band of plasmonic waveguide modes from degenerated single-particle modes in detail. In striking difference from plasmonic rod-like structures, the plasmon band is confined in excitation energy, which allows light manipulations below the diffraction limit. The non-degenerated surface plasmon modes show suppressed radiative losses for efficient energy propagation over a distance of 1500 nm.

Published
2019
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4. Efficient energy propagation through self-assembled gold nanoparticle chain waveguides

Author

Gür, Fatih N., McPolin, Cillian P. T., Raza, Søren, Mayer, Martin, Roth, Diane J., Steiner, Anja Maria, Löffler, Markus, Fery, Andreas, Brongersma, Mark L., Zayats, Anatoly V., König, Tobias A. F., and Schmidt, Thorsten L.

Subjects
Physics - Optics
Abstract

The strong interaction of light with metallic nanoparticles enables field confinement well below the diffraction limit. Plasmonic waveguides consisting of metal nanoparticle chains could be used for the propagation of energy or information on the nanoscale, but high losses have thus far impeded practical applications. Here we demonstrate that efficient waveguiding is possible through gold nanoparticle chains despite the high dissipative losses of gold. A DNA origami directed self-assembly of monocrystalline, spherical nanoparticles allows the interparticle spacing to be decreased to 2 nm or below, which gives rise to lower-energy plasmon resonance modes. Our simulations imply that these lower energy modes allow efficient waveguiding but collapse if interparticle gap sizes are increased. Individual waveguides are characterized with nanometer-resolution by electron energy loss spectroscopy, and directed propagation of energy towards a fluorescent nanodiamond and nanoscale energy conversion is shown by cathodoluminescence imaging spectroscopy on a single-device level. With this approach, micrometer-long propagation lengths might be achieved, enabling applications in information technology, sensing and quantum optics.

Published
2017

5. Ultrasonic Control of Polymer-Capped Plasmonic Molecules

Author

Cai, Yingying, Sarkar, Swagato, Peng, Yuwen, König, Tobias A. F., and Vana, Philipp

Abstract

Plasmonic molecules (PMs) composed of polymer-capped nanoparticles represent an emerging material class with precise optical functionalities. However, achieving controlled structural changes in metallic nanoparticle aggregation at the nanoscale, similar to the modification of atomic structures, remains challenging. This study demonstrates the 2D/3D isomerization of such plasmonic molecules induced by a controlled ultrasound process. We used two types of gold nanoparticles, each functionalized with hydrogen bonding (HB) donor or acceptor polymers, to self-assemble into different ABN-type complexes via interparticle polymer bundles acting as molecular bonds. Post-ultrasonication treatment significantly shortens these bonds from approximately 14 to 2 nm by enhancing HB cross-linking within the bundles. This drastic change in the bond length increases the stiffness of the resulting clusters, facilitating the transition from 2D to 3D configurations in 100% yield during drop-casting onto substrates. Our results advance the precise control of PMs’ nanoarchitectures and provide insights for their broad applications in sensing, optoelectronics, and metamaterials.

Published
2024
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10. Dynamic Tunable Chiral Plasmonic Properties via Self‐Assembly on Helical Threads.

Author

Guo, Zhen, Sarkar, Swagato, Liu, Rongying, Zhang, Ying, Sheng, Qing‐Tao, Chen, Guosong, König, Tobias A. F., and Ye, Chunhong

Subjects
PLASMONICS, CIRCULAR dichroism, ELECTROSTATIC interaction, ELECTROMAGNETIC fields, OPTICAL properties, SPUN yarns, CHIRALITY of nuclear particles
Abstract

Tailorable chiral plasmonic nanostructures have attracted great interest due to their potential applications in photonics and sensing. However, there are limited straightforward fabrication routes to modulate the morphology of chiral materials with an external stimulus. Here, a helical assembly of gold nanospheres (AuNSs) is successfully obtained via self‐assembly using glycopeptide helical nanofibers as templates based on electrostatic interactions. The assembly morphology can be readily tailored from short debris to single‐/double‐ and multiple helical threads by changing pHs, resulting in well‐controlled modulation of circular dichroism (CD) in the visible range. Further, this tunable assembly and corresponding chiroptical properties are fully reversible in the pH range from 6 to 10. The electromagnetic simulation revealed how the structural geometries of AuNS helices changed the electromagnetic field propagation pattern to facilitate corresponding chiral optical properties. This approach is a unique and facilely obtained example of chiral nanomaterials with in situ tailoring morphology and chiral properties through external stimulus, demonstrating a potential application for biosensing. [ABSTRACT FROM AUTHOR]

Published
2024
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13. A Quasi‐2D Polypyrrole Film with Band‐Like Transport Behavior And High Charge Carrier Mobility

Author

Liu, Kejun, primary, Réhault, Julien, additional, Liang, Baokun, additional, Hambsch, Mike, additional, Zhang, Yingying, additional, Seçkin, Sezer, additional, Zhou, Yunxia, additional, Shivhare, Rishi, additional, Zhang, Peng, additional, Polozij, Miroslav, additional, König, Tobias A. F., additional, Qi, Haoyuan, additional, Zhou, Shengqiang, additional, Fery, Andreas, additional, Mannsfeld, Stefan C. B., additional, Kaiser, Ute, additional, Heine, Thomas, additional, Banerji, Natalie, additional, Dong, Renhao, additional, and Feng, Xinliang, additional

Published
2023
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18. The Rise of Structurally Anisotropic Plasmonic Janus Gold Nanostars.

Author

Singh, Prem, Kundu, Koustav, Seçkin, Sezer, Bhardwaj, Keshav, König, Tobias A. F., and Jaiswal, Amit

Subjects
SERS spectroscopy, JANUS particles, KINETIC control, PLASMONICS, GOLD
Abstract

Nanostructures intrinsically possessing two different structural or functional features, often called Janus nanoparticles, are emerging as a potential material for sensing, catalysis, and biomedical applications. Herein, we report the synthesis of plasmonic gold Janus nanostars (NSs) possessing a smooth concave pentagonal morphology with sharp tips and edges on one side and, contrastingly, a crumbled morphology on the other. The methodology reported herein for their synthesis – a single‐step growth reaction – is different from any other Janus nanoparticle preparation involving either template‐assisted growth or a masking technique. Interestingly, the coexistence of lower‐ and higher‐index facets was found in these Janus NSs. The general paradigm for synthesizing gold Janus NSs was investigated by understanding the kinetic control mechanism with the combinatorial effect of all the reagents responsible for the structure. The optical properties of the Janus NSs were realized by corelating their extinction spectra with the simulated data. The size‐dependent surface‐enhanced Raman scattering (SERS) activity of these Janus NSs was studied with 1,4‐BDT as the model analyte. Finite‐difference time‐domain simulations for differently sized particles revealed the distribution of electromagnetic hot‐spots over the particles resulting in enhancement of the SERS signal in a size‐dependent manner. [ABSTRACT FROM AUTHOR]

Published
2023
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20. A Quasi-2D Polypyrrole Film with Band-Like Transport Behavior And High Charge Carrier Mobility

Author

Liu, Kejun, Réhault, Julien, Liang, Baokun, Hambsch, Mike, Zhang, Yingying, Seçkin, Sezer, Zhou, Yunxia, Shivhare, Rishi, Zhang, Peng, Polozij, Miroslav, König, Tobias A F, Qi, Haoyuan, Zhou, Shengqiang, Fery, Andreas, Mannsfeld, Stefan C B, Kaiser, Ute, Heine, Thomas, Banerji, Natalie, Dong, Renhao, and Feng, Xinliang

Subjects
540 Chemistry, 570 Life sciences, biology, 000 Computer science, knowledge & systems
Abstract

Quasi-two-dimensional conjugated polymers (q2DCPs) are polymers that consist of linear conjugated polymer chains assembled through non-covalent interactions to form a layered structure. In this work, w e report the synthesis of a novel crystalline q2D polypyrrole (q2DPPy) film at an air/H2 SO4 (95%) interface. The unique interfacial environment facilitated chain extension, prevented disorder, and resulted in a crystalline, layered assembly of protonated quinoidal chains with a fully extended conformation in its crystalline domains. This unique structure features highly delocalized π-electron systems within the extended chains, which is responsible for the low effective mass and narrow electronic bandgap. Thus w e investigated the temperature-dependent charge transport properties of q2DPPy using the van der Pauw (vdP) method and terahertz time-domain spectroscopy (THz-TDS). The vdP method revealed that the q2DPPy film exhibited a semiconducting behavior with a thermally activated hopping mechanism in long-range transport between the electrodes. Conversely, THz-TDS revealed a band-like transport, indicating intrinsic charge transport up to a record short-range high THz mobility of ∼107.1 cm2 V-1 s-1 . This article is protected by copyright. All rights reserved.

Published
2023
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24. Anisotropic and non-linear optical properties of self-assembled colloidal metasurfaces

Author

König, Tobias A. F., Eychmüller, Alexander, Technische Universität Dresden, Leibniz-Institut für Polymerforschung Dresden e.V., Aftenieva, Olha, König, Tobias A. F., Eychmüller, Alexander, Technische Universität Dresden, Leibniz-Institut für Polymerforschung Dresden e.V., and Aftenieva, Olha

Abstract

Photonic metasurfaces obtain their unique optical properties from the periodic arrangement of sub-wavelength building blocks and can manipulate light in ways that differ significantly from bulk materials. Until recently, metasurfaces have been fabricated using top-down methods on a limited surface area. With the development of directed self-assembly methods and utilization of nanoscale colloids, metasurfaces can be fabricated on a larger scale and with reasonable efforts. In particular, soft nanoimprint lithography, based on the controlled drying of the colloidal solution within a structured template, allows for the precise placement of versatile colloidal building blocks on a substrate of choice. In this dissertation, the material and optical properties of self-assembled plasmonic and photoluminescent nanoparticles are systematically studied in terms of their short- and long-range interactions. It is shown that 1D plasmonic lattices exploit the intrinsic anisotropy and substrate-dependent collective resonant coupling. Likewise, semiconductor nanoparticles organized into linear gratings, result in light-emitting metasurfaces, featuring geometry-dependent amplification of the photoluminescence that can be further promoted to a non-linear amplification regime. Moreover, on flexible substrates, these self-assembled light-emitting metasurfaces can be stacked and twisted, inducing remarkably strong chiral effects and subsequently used for directional light sources, nanolasers, sensing, and labeling applications. Supported by theoretical modeling, this work provides a novel approach to realize anisotropic and non-linear optical properties on centimeter-scaled surface area using soft-lithography and directed self-assembly methods. It bridges the gap between nanoscale colloids and optoelectronics while advancing the integration of metasurfaces into functional devices., Photonische Metaoberflächen erhalten ihre einzigartigen optischen Eigenschaften durch die periodische Anordnung von Bauelementen im Sub-Wellenlängenbereich und können Licht auf eine Weise manipulieren, die sich deutlich von Ausgangsmaterialien unterscheidet. Bis vor kurzem wurden Metaoberflächen mit Top-Down-Methoden auf einer begrenzten Oberfläche hergestellt. Mit der Entwicklung von Methoden der gerichteten Selbstorganisation und der Nutzung von Kolloiden im Nanomaßstab können Metaoberflächen in größerem Maßstab und mit angemessenem Aufwand hergestellt werden. Insbesondere die Soft-Nanoimprint-Lithographie, die auf der kontrollierten Trocknung der kolloidalen Lösung innerhalb einer strukturierten Template basiert, ermöglicht die präzise Platzierung vielseitiger kolloidaler Bauelemente auf einem Substrat der Wahl. In dieser Dissertation werden die materiellen und optischen Eigenschaften selbstorganisierter plasmonischer und photolumineszenter Nanopartikel im Hinblick auf ihre Kurz- und Langstreckenwechselwirkungen systematisch untersucht. Es wird gezeigt, dass plasmonische 1D-Gitter die intrinsische Anisotropie und die substratabhängige kollektive Resonanzkopplung ausnutzen. Ebenso führen Halbleiter-Nanopartikel, die in linearen Gittern organisiert sind, zu lichtemittierenden Metaoberflächen, welche eine geometrieabhängige Verstärkung der Photolumineszenz aufweisen, die bis zu einem nichtlinearen Verstärkungsregime weitergeführt werden kann. Außerdem können diese selbstorganisierten, lichtemittierenden Metaoberflächen auf flexiblen Substraten gestapelt und verdreht werden, was zu bemerkenswert starken chiralen Effekten führt und anschließend für gerichtete Lichtquellen, Nanolaser, Sensor- und Beschriftungsanwendungen genutzt werden kann. Unterstützt durch theoretische Modellierung bietet diese Arbeit einen neuartigen Ansatz zur Realisierung anisotroper und nichtlinearer optischer Eigenschaften auf zentimetergroßen Oberflächen unter Verwendung von Softlithographie u

Published
2022

25. High Yield Synthesis of Water-Processable Donor : Acceptor Janus Nanoparticles with Tuned Internal Morphology and Highly Efficient Charge Separation/Transfer

Author

Du, Yixuan, Li, Yue, Aftenieva, Olha, Tsuda, Takuya, Formanek, Petr, König, Tobias A. F., and Synytska, Alla

Subjects
transient photoluminescence, optoelectronic applications, charge separation/transfer properties, donor–acceptor Janus nanoparticles, steady-state photoluminsecence, water-processable Janus particles, energy-filtered transmission electron microscopy
Published
2022
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31. Functional colloidal surface assemblies: Classical optics meets template-assisted self-assembly

Author

König, Tobias A. F., Eychmüller, Alexander, Technische Universität Dresden, Leibniz-Institut für Polymerforschung Dresden e.V., Gupta, Vaibhav, König, Tobias A. F., Eychmüller, Alexander, Technische Universität Dresden, Leibniz-Institut für Polymerforschung Dresden e.V., and Gupta, Vaibhav

Abstract

When noble metals particles are synthesized with progressively smaller dimensions, strikingly novel optical properties arise. For nanoscale particles, collective disturbances of the electron density known as localized surface plasmons resonances can arise, and these resonances are utilized in a variety of applications ranging from surface-enhanced molecular spectroscopy and sensing to photothermal cancer therapy to plasmon-driven photochemistry. Central to all of these studies is the plasmon’s remarkable ability to process light, capturing and converting it into intense near fields, heat, and even energetic carriers at the nanoscale. In the past decade, we have witnessed major advances in plasmonics which is directly linked with the much broader field of (colloidal) nanotechnology. These breakthroughs span from plasmon lasing and waveguides, plasmonic photochemistry and solar cells to active plasmonics, plasmonics nanocomposites and semiconductor plasmons. All the above-mentioned phenomena rely on precise spatial placement and distinct control over the dimensions and orientation of the individual plasmonic building blocks within complex one-, two- or three-dimensional complex arrangements. For the nanofabrication of metal nanostructures at surfaces, most often lithographic approaches, e.g. e-beam lithography or ion-beam milling are generally applied, due to their versatility and precision. However, these techniques come along with several drawbacks such as limited scalability, limited resolution, limited compatibility with silicon manufacturing techniques, damping effects due to the polycrystalline nature of the metal nanostructures and low sample throughput. Thus, there is a great demand for alternative approaches for the fabrication of metal nanostructures to overcome the above-mentioned limitations. But why colloids? True three-dimensionality, lower damping, high quality modes due to mono-dispersity, and the absence of grain boundaries make the colloida

Published
2020

39. Template-assisted colloidal self-assembly of macroscopic magnetic metasurfaces† †Electronic supplementary information (ESI) available: Additional simulations, experimental details, optical data and effective optical parameters are provided. See DOI: 10.1039/c6fd00013d Click here for additional data file

Author

Mayer, Martin, Tebbe, Moritz, Kuttner, Christian, Schnepf, Max J., König, Tobias A. F., and Fery, Andreas

Subjects
Chemistry
Abstract

We demonstrate a template-assisted colloidal self-assembly approach for magnetic metasurfaces on macroscopic areas. The choice of anisotropic colloidal particle geometry, assembly pattern and metallic film is based on rational design criteria, taking advantage of mirror-charge effects for gold nanorods placed on gold film. Monodisperse gold nanorods prepared utilizing wet-chemistry are arranged with high precision on wrinkled templates to form linear array-type assemblies and subsequently transferred to a thin gold film. Due to the obtained particle-to-film distance of 1.1 nm, the plasmonic mode of the nanorod is able to couple efficiently with the supporting metallic film, giving rise to a magnetic mode in the visible spectrum (721 nm). Conventional UV-vis-NIR measurements in close correlation with electromagnetic simulations provide evidence for the presence of a magnetic resonance on the macroscopic area. The herein presented scalable lithography-free fabrication process paves the road towards colloidal functional metasurfaces with an optical response in the effective magnetic permeability.

Published
2016

41. All-Optical Reversible Azo-Based Wrinkling Patterns with High Aspect Ratio and Polarization-Independent Orientation for Light-Responsive Soft Photonics

Author

Wang, Juanjuan, primary, Zheng, Yang, additional, Li, Lele, additional, Liu, Enping, additional, Zong, Chuanyong, additional, Zhao, Jingxin, additional, Xie, Jixun, additional, Xu, Fan, additional, König, Tobias A. F., additional, Grenzer Saphiannikova, Marina, additional, Cao, Yanping, additional, Fery, Andreas, additional, and Lu, Conghua, additional

Published
2019
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47. Particles at interfaces : general discussion

Author

Striolo, Alberto, Kim, Jongwook, Murphy, Catherine, Liz-Marzán, Luis, Lahann, Joerg, Reguera, Javier, Zhou, Yu, Brust, Mathias, Thill, Antoine, Scarabelli, Leonardo, König, Tobias A. F., Buzza, Martin, Kuttner, Christian, Gonzalez Solveyra, Estefania, Wolf, Heiko, Vermant, Jan, Pauly, Matthias, Harvie, Andrew, Pasquato, Lucia, Stocco, Antonio, Mattoussi, Hedi, Kumacheva, Eugenia, Heatley, Kelley, Hanske, Christoph, Faller, Roland, French, David, Honciuc, Andrei, Binks, Bernard, Sicard, Francois, Striolo, Alberto, Kim, Jongwook, Murphy, Catherine, Liz-Marzán, Luis, Lahann, Joerg, Reguera, Javier, Zhou, Yu, Brust, Mathias, Thill, Antoine, Scarabelli, Leonardo, König, Tobias A. F., Buzza, Martin, Kuttner, Christian, Gonzalez Solveyra, Estefania, Wolf, Heiko, Vermant, Jan, Pauly, Matthias, Harvie, Andrew, Pasquato, Lucia, Stocco, Antonio, Mattoussi, Hedi, Kumacheva, Eugenia, Heatley, Kelley, Hanske, Christoph, Faller, Roland, French, David, Honciuc, Andrei, Binks, Bernard, and Sicard, Francois

Published
2018

48. Tunable Circular Dichroism by Photoluminescent Moiré Gratings.

Author

Aftenieva, Olha, Schnepf, Max, Mehlhorn, Börge, and König, Tobias A. F.

Subjects
SEMICONDUCTOR nanocrystals, PHOTOLUMINESCENCE, CIRCULAR dichroism
Abstract

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. [ABSTRACT FROM AUTHOR]

Published
2021
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49. Mechanotunable Plasmonic Properties of Colloidal Assemblies.

Author

Brasse, Yannic, Gupta, Vaibhav, Schollbach, H. C. Tomohiro, Karg, Matthias, König, Tobias A. F., and Fery, Andreas

Subjects
SURFACE plasmon resonance, ELECTROMAGNETIC waves, FLEXIBLE structures, METAL nanoparticles, LATTICE theory, PRECIOUS metals, POLARITONS, JANUS particles
Abstract

Noble metal nanoparticles can absorb incident light very efficiently due to their ability to support localized surface plasmon resonances (LSPRs), collective oscillations of the free electron cloud. LSPRs lead to strong, nanoscale confinement of electromagnetic energy which facilitates applications in many fields including sensing, photonics, or catalysis. In these applications, damping of the LSPR caused by inter‐ and intraband transitions is a limiting factor due to the associated energy losses and line broadening. The losses and broad linewidth can be mitigated by arranging the particles into periodic lattices. Recent advances in particle synthesis, (self‐)assembly, and fabrication techniques allow for the realization of collective coupling effects building on various particle sizes, geometries, and compositions. Beyond assemblies on static substrates, by assembling or printing on mechanically deformable surfaces a modulation of the lattice periodicity is possible. This enables significant alteration and tuning of the optical properties. This progress report focuses on this novel approach for tunable spectroscopic properties with a particular focus on low‐cost and large‐area fabrication techniques for functional plasmonic lattices. The report concludes with a discussion of the perspectives for expanding the mechanotunable colloidal concept to responsive structures and flexible devices. [ABSTRACT FROM AUTHOR]

Published
2020
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