Universität Stuttgart
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Item Open Access Dimerization and oligomerization of DNA-assembled building blocks for controlled multi-motion in high-order architectures(2021) Xin, Ling; Duan, Xiaoyang; Liu, NaIn living organisms, proteins are organized prevalently through a self-association mechanism to form dimers and oligomers, which often confer new functions at the intermolecular interfaces. Despite the progress on DNA-assembled artificial systems, endeavors have been largely paid to achieve monomeric nanostructures that mimic motor proteins for a single type of motion. Here, we demonstrate a DNA-assembled building block with rotary and walking modules, which can introduce new motion through dimerization and oligomerization. The building block is a chiral system, comprising two interacting gold nanorods to perform rotation and walking, respectively. Through dimerization, two building blocks can form a dimer to yield coordinated sliding. Further oligomerization leads to higher-order structures, containing alternating rotation and sliding dimer interfaces to impose structural twisting. Our hierarchical assembly scheme offers a design blueprint to construct DNA-assembled advanced architectures with high degrees of freedom to tailor the optical responses and regulate multi-motion on the nanoscale.Item Open Access Transformable plasmonic helix with swinging gold nanoparticles(2022) Peil, Andreas; Zhan, Pengfei; Duan, Xiaoyang; Krahne, Roman; Garoli, Denis; M. Liz‐Marzán, Luis; Liu, NaControl over multiple optical elements that can be dynamically rearranged to yield substantial three‐dimensional structural transformations is of great importance to realize reconfigurable plasmonic nanoarchitectures with sensitive and distinct optical feedback. In this work, we demonstrate a transformable plasmonic helix system, in which multiple gold nanoparticles (AuNPs) can be directly transported by DNA swingarms to target positions without undergoing consecutive stepwise movements. The swingarms allow for programmable AuNP translocations in large leaps within plasmonic nanoarchitectures, giving rise to tailored circular dichroism spectra. Our work provides an instructive bottom‐up solution to building complex dynamic plasmonic systems, which can exhibit prominent optical responses through cooperative rearrangements of the constituent optical elements with high fidelity and programmability.Item Open Access Gold nanoparticle-mediated DNA origami nanoarchitectures(2024) Peil, Andreas; Na Liu, Laura (Prof. Dr.)Since its origin in the 1980s, DNA (deoxyribonucleic acid) nanotechnology has established itself as a captivating nanofabrication technique with ever increasing impact that combines aspects from physics, chemistry, and biology to construct artificial nanosystems by means of molecular self assembly. Within the field of DNA nanotechnology, the DNA origami technique represents one of the most versatile fabrication tools to craft functional two-dimensional (2D) and three-dimensional (3D) nanostructures from the bottom up. These structures offer precisely tailored geometries along with programmable functions, featuring positional addressability with sub-5 nm resolution and exceptional spatiotemporal accuracy. This thesis discusses strategies to employ the DNA origami technique to assemble intricate hybrid nanosystems with synergistically integrated gold nanoparticles (AuNPs). The AuNPs take over different roles; they grant (i) structural and (ii) functional features and enable the (iii) optical monitoring of the systems. This approach allows the fabrication of nanostructures piece by piece to explore their structural and functional properties at the nanoscale in detail. The first publication covers different strategies for the hierarchical assembly of topological DNA origami structures using a AuNP-templated self-assembly approach. The assembly of [2], [3], and [4]catenanes with interconnecting AuNPs is elucidated. The AuNPs can be controllably released to disconnect the individual rings, leaving only the mechanical bond of the catenane chain. In the second publication, a dynamic AuNP-DNA origami gear system is presented that is designed to emulate a planetary gearset with precise spatiotemporal control over its rotation dynamics. The AuNPs serve three crucial tasks. They (i) structurally link the origami ring modules, (ii) mediate the rotation and (iii) enable the real time optical tracking of the rotation via fluorescence spectroscopy. The system enables tightly orchestrated and programmable bidirectional rotations. In the third publication, reconfigurable chiral metastructures comprising multiple plasmonic particles that are accurately positioned in a helical manner around a DNA origami template are discussed. The implementation of a DNA ‘swingarm strategy’ enables the simultaneous and efficient relocation of multiple closely spaced AuNPs over large distances to precisely tune the chiroptical response of the system. The presented publications illustrate the beneficial synergies between DNA origami systems and rationally integrated AuNPs with the aim to advance and expand the application spectrum of these hybrid nanosystems within their scientific disciplines.Item Open Access Stabilizing γ‐MgH2 at nanotwins in mechanically constrained nanoparticles(2021) Kammerer, Jochen A.; Duan, Xiaoyang; Neubrech, Frank; Schröder, Rasmus R.; Liu, Na; Pfannmöller, MartinReversible hydrogen uptake and the metal/dielectric transition make the Mg/MgH2 system a prime candidate for solid‐state hydrogen storage and dynamic plasmonics. However, high dehydrogenation temperatures and slow dehydrogenation hamper broad applicability. One promising strategy to improve dehydrogenation is the formation of metastable γ‐MgH2. A nanoparticle (NP) design, where γ‐MgH2 forms intrinsically during hydrogenation is presented and a formation mechanism based on transmission electron microscopy results is proposed. Volume expansion during hydrogenation causes compressive stress within the confined, anisotropic NPs, leading to plastic deformation of β‐MgH2 via (301)β twinning. It is proposed that these twins nucleate γ‐MgH2 nanolamellas, which are stabilized by residual compressive stress. Understanding this mechanism is a crucial step toward cycle‐stable, Mg‐based dynamic plasmonic and hydrogen‐storage materials with improved dehydrogenation. It is envisioned that a more general design of confined NPs utilizes the inherent volume expansion to reform γ‐MgH2 during each rehydrogenation.Item Open Access High yield purification of an isoleucine zipper-modified CD95 ligand for efficient cell apoptosis initiation and with biotin or DNA-oligomer binding domain to probe ligand functionalization effects(2025) Shang, Xiaoyue; Bartels, Nina; Weck, Johann Moritz; Suppmann, Sabine; Basquin, Jérôme; Thaventhiran, Gajen; Heuer-Jungemann, Amelie; Monzel, CorneliaBackground. Cluster of differentiation 95 (CD95/Fas/Apo1) as part of the Tumor-necrosis factor (TNF) receptor family is a prototypic trigger of the ‘extrinsic’ apoptotic pathway and its activation by the trimeric ligand CD95L is of high interest. However, CD95L, when presented in solution, exhibits a low efficiency to induce apoptosis signaling in human cells. Results. Here, we design a recombinant CD95L exhibiting an isoleucine zipper (IZ) motif at the N-terminus for stabilization of the trimerized CD95L and demonstrate its high apoptosis initiation efficiency. This efficiency is further enhanced by antibody-mediated crosslinking of IZ-CD95L.A cysteine amino acid fused behind the IZ is used as a versatile coupling site for bionanotechnological applications or for the development of biomedical assays. A fast, cheap, and efficient production of CD95L via the HEK293T secretory expression system is presented, along with CD95L affinity purification and functionalization. We verified the biological activity of the purified protein and identified a stabilized trimeric CD95L structure as the most potent inducer of apoptosis signaling. Conclusions. The workflow and the findings reported here will streamline a wide array of future low- or high-throughput TNF-ligand screens, and their modification towards improving apoptosis induction efficiency and, potentially, anticancer therapy.Item Open Access Real-time tracking of coherent oscillations of electrons in a nanodevice by photo-assisted tunnelling(2024) Luo, Yang; Neubrech, Frank; Martin-Jimenez, Alberto; Liu, Na; Kern, Klaus; Garg, ManishCoherent collective oscillations of electrons excited in metallic nanostructures (localized surface plasmons) can confine incident light to atomic scales and enable strong light-matter interactions, which depend nonlinearly on the local field. Direct sampling of such collective electron oscillations in real-time is crucial to performing petahertz scale optical modulation, control, and readout in a quantum nanodevice. Here, we demonstrate real-time tracking of collective electron oscillations in an Au bowtie nanoantenna, by recording photo-assisted tunnelling currents generated by such oscillations in this quantum nanodevice. The collective electron oscillations show a noninstantaneous response to the driving laser fields with a T2 decay time of nearly 8 femtoseconds. The contributions of linear and nonlinear electron oscillations in the generated tunnelling currents were precisely determined. A phase control of electron oscillations in the nanodevice is illustrated. Functioning in ambient conditions, the excitation, phase control, and read-out of coherent electron oscillations pave the way toward on-chip light-wave electronics in quantum nanodevices.Item Open Access Electrochemically addressable conducting polymer-based dynamic metasurfaces for spatiotemporal light control at visible frequencies(2025) Kaißner, Robin; Liu, Laura Na (Prof. Dr.)Item Open Access Floating zone growth of large tetragonal Ruddlesden-Popper bilayer nickelate YySr3-yNi2-xAlxO7-δ single crystals(2025) Yilmaz, Hasan; Sosa-Lizama, Pablo; Knauft, Manuel; Küster, Kathrin; Starke, Ulrich; Isobe, Masahiko; Clemens, Oliver; Aken, Peter A. van ; Suyolcu, Y. E.; Puphal, PascalThe discovery of superconductivity under high pressure in Ruddlesden-Popper (RP) type phase bilayer La3Ni22.5+O7 and trilayer La4Ni32.66+O10 has initiated the frontier of nickelate-based superconductors. In this context, RP-type phases within the Sr-Ni-O system offer promising alternatives as they offer unconventional high oxidation states and Sr-T-O comprises the usual RP series. Here, the intrinsic stability of the undoped Sr-Ni-O framework is investigated using density functional theory (DFT). While Sr3Ni2O7 (SNO) is stable synthesis so far requires Al co-substition in Sr3Ni2-xAlxO7-δ (SNAO). Y-doping resulting in YySr3-yNi2-xAlxO7-δ (YSNAO) effectively mitigates the challenge posed by an insulating ground state. This modification yields a substantial reduction in resistivity, with the crystals exhibiting semiconducting behavior. To explore phase formation within the narrow compositional window of the Y-Sr-Ni-Al-O system, single crystals were grown using the optical floating zone (OFZ) technique under an oxygen partial pressure of approximately 10 bar. The optimized growth conditions for YSNAO enabled the production of large (6 × 5 x 3 mm3), high-quality crystals suitable for neutron scattering experiments. In the absence of Al, crystal growth yielded the n = 1 RP phase Sr1.66Y0.33NiO4-δ, for which single crystals were obtained. The structural, chemical, electrical, and magnetic properties of both the as-grown and topochemically reduced YSNAO compounds were comprehensively characterized through diffraction, spectroscopy, transport, and magnetization measurements.Item Open Access DNA‑directed assembly of photonic nanomaterials for diagnostic and therapeutic applications(2025) Ding, Longjiang; Liu, Bing; Peil, Andreas; Fan, Sisi; Chao, Jie; Liu, NaDNA‐directed assembly has emerged as a versatile and powerful approach for constructing complex structured materials. By leveraging the programmability of DNA nanotechnology, highly organized photonic systems can be developed to optimize light‐matter interactions for improved diagnostics and therapeutic outcomes. These systems enable precise spatial arrangement of photonic components, minimizing material usage, and simplifying fabrication processes. DNA nanostructures, such as DNA origami, provide a robust platform for building multifunctional photonic devices with tailored optical properties. This review highlights recent progress in DNA‐directed assembly of photonic nanomaterials, focusing on their applications in diagnostics and therapeutics. It provides an overview of the latest advancements in the field, discussing the principles of DNA‐directed assembly, strategies for functionalizing photonic building blocks, innovations in assembly design, and the resulting optical effects that drive these developments. The review also explores how these photonic architectures contribute to diagnostic and therapeutic applications, emphasizing their potential to create efficient and effective photonic systems tailored to specific healthcare needs.Item Open Access Meta-optics redefines microdisplay : monolithic color LCoS without polarization dependency(2025) Ou, Xiangnian; Hu, Yueqiang; Yu, Dian; Liu, Shulin; Lou, Shaozhen; Shu, Zhiwen; Wei, Wenzhi; Liu, Man; Li, Jianxiong; Chang, Tianhai; Liu, Na; Duan, HuigaoLiquid crystal on silicon (LCoS) panels are pivotal to high-resolution optical projection and imaging displays, yet their inherent polarization sensitivity and reliance on multi-chip architectures for color reproduction constrain the upper limit of light utilization, increase system complexity and restrict broader applicability. Here, we demonstrate a monolithic color meta-LCoS prototype that integrates dual-layer metasurfaces to achieve polarization-insensitive, full-color amplitude modulation on a single chip. Polarization sensitivity is eliminated via a synergistic design combining metasurface-enabled polarization conversion and voltage-controlled liquid crystal phase modulation, achieving a high-contrast, polarization-insensitive optical switch. By embedding red, green, and blue metasurface subpixels and meticulously designed off-axis angles, enabling direct color synthesis through a unified device. We showcase a 64-pixel monochrome and a 9-pixel color prototype capable of dynamically projecting diverse patterns under unpolarized illumination. Fully compatible with existing LCoS fabrication processes, our device significantly reduces system complexity and cost, offering transformative applications in next-generation projectors and AR/VR displays.