arXiv subjects

Tim Liedl

Publications and source records attributed to Tim Liedl.

18 recordsLinked to original sources

arXiv2026

Directed assembly of tetrahedral patchy particles

Colloidal particles with prescribed valency such as the tetrahedral patchy particles have long been seen as a viable route to technologically relevant open lattice structures on the scale of hundreds of nanometers. However, conceptual limitations and resulting competing local bonding configurations often lead to mixed lattice phases. Here, we present a DNA-origami enabled approach to controlling the attachment of tetrapod building blocks in predictable ways. By varying the relative strength of two designed binding configurations we are able to direct the assembly of tetrapod particles into diamond cubic, twinned diamonds, stacking-disordered mixtures, hexagonal diamonds, and sII clathrates. Under specific conditions, the diamond structures are interpenetrated by additional networks, resulting in triple cubic and triple hexagonal diamond structures. The 440 nm large unit cell of the clathrates shifts structural reflections into the visible range, giving these rationally designed, self-assembled crystals structural color.

cond-mat.soft↗

arXiv2025

Tunable dynamics of flexible magnetic microcrosses: synchronous rotation, breathing and out-of-plane arm overtaking

We combine colloidal self-assembly and soft-lithography techniques to realize flexible magnetic microcrosses that can be manipulated via external, time dependent magnetic fields. The crosses are characterized by a central domain connected via four flexible arms. When subjected to an in-plane, rotating magnetic field, the crosses transit from a synchronous to an asynchronous spinning motion where their average rotation decreases with the driving frequency. In the asynchronous regime and at low field amplitudes, the crosses display a breathing mode, characterized by relative oscillations between the arms, while remaining localized in the two dimensional plane. In contrast, for high field amplitudes, we observe an arm overtaking regime where two opposite filaments surpass the remaining ones forcing the cross to perform a three-dimensional gyroscopic-like rotation. Using slender body theory and balancing the effect of magnetic and elastic interactions, we recover the experimental findings and show that the overtaking regime occurs due to different arm magnetizations. Our engineered microscopic colloidal rotors characterized by multiple flexible filaments may find potential applications for precise lab-on-a-chip operations or as stirrers dispersed within microfluidic or biological channels.

cond-mat.soft↗

arXiv2025

High-endurance mechanical switching in a DNA origami snap-through mechanism

Switchable elements are key components of dynamic technological and biological systems, enabling reversible transitions between well-defined states. Here, we present a DNA origami-based, mechanically bistable snap-through mechanism that can be electrically controlled. This nanoscale switch exhibits long-term stability in both states in the absence of external stimuli, while achieving millisecond-scale switching times upon application of an electric field. Individual devices sustain hundreds of thousands of switching cycles over several hours, offering a powerful platform for systematically studying the endurance and failure mechanisms of biomolecular nanoswitches. Functionalization with a gold nanorod further allows polarization-dependent optical modulation, opening avenues for applications in plasmonics. This versatile electromechanical interface has potential uses in molecular information processing, optical nanodevices, and the dynamic control of chemical reactions.

physics.app-ph↗

arXiv2025

Deterministic and Scalable Quantum Light Generation in DNA Origami-Programmed Organic Molecule-MoS$_2$ Monolayer Hybrids

The functionalization of atomically-thin transition metal dichalcogenides (TMDs) with organic molecules is a promising approach for realizing nanoscale optoelectronic devices with tailored functionalities, such as quantum light generation or p-n junctions. However, achieving precise control over the molecules' positioning on the 2D material remains a significant challenge. Here, we overcome the limitations of solution- and vapor-deposition methods and use a DNA origami placement technique to spatially arrange thiol molecules on a chip surface at the single-molecule level with high assembly yields. We successfully integrated MoS$_2$ monolayers with micron-scale thiol-origami patterns, achieving single-photon emission from thiol-induced localized excitons in MoS$_2$. Our work lays a foundation for the chemical control of quantum emitters in atomically-thin semiconductors and enables the design and production of ultracompact 2D devices for quantum technologies.

cond-mat.mes-hall↗

arXiv2024

Fabrication of functional 3D nanoarchitectures via atomic layer deposition on DNA origami crystals

While DNA origami is a powerful bottom-up fabrication technique, the physical and chemical stability of DNA nanostructures is generally limited to aqueous buffer conditions. Wet chemical silicification can stabilise these structures but does not add further functionality. Here, we demonstrate a versatile 3D nanofabrication technique to conformally coat micrometre-sized DNA origami crystals with functional metal oxides via atomic layer deposition (ALD). In addition to depositing homogenous and conformal nanometre-thin ZnO, TiO2, and IrO2 (multi)layers inside SiO2-stablised crystals, we establish a method to directly coat bare DNA crystals with ALD layers while maintaining the crystal integrity, enabled by critical point drying and low ALD process temperatures. As a proof-of-concept application, we demonstrate electrocatalytic water oxidation using ALD IrO2-coated DNA origami crystals, resulting in improved performance relative to planar films. Overall, our coating strategy establishes a tool set for designing custom-made 3D nanomaterials with precisely defined topologies and material compositions, combining the unique advantages of DNA origami and atomically controlled deposition of functional inorganic materials.

physics.app-ph↗

arXiv2024

Hot electrons and electromagnetic effects in the broadband Au, Ag, and Ag-Au nanocrystals: The UV, visible, and NIR plasmons

Energetic and optical properties of plasmonic nanocrystals strongly depend on their sizes, shapes, and composition. Whereas using plasmonic nanoparticles in biotesting has become routine, applications of plasmonics in energy are still early in development. Here, we investigate hot electron (HE) generation and related electromagnetic effects in both mono- and bi-metallic nanorods (NRs) and focus on one promising type of bi-metallic nanocrystals - core-shell Au-Ag nanorods. The spectra of the NRs are broadband, highly tunable with their geometry, and have few plasmon resonances. In this work, we provide a new quantum formalism describing the HE generation in bi-metallic nanostructures. Interestingly, we observe that the HE generation rate at the UV plasmon resonance of Au-Ag NRs appears to be very high. These HEs are highly energetic and suitable for carbon-fuel reactions. Simultaneously, the HE generation at the longitudinal plasmon (L-plasmon) peaks, which can be tuned from the yellow to near-IR, depends on the near-field and electromagnetic Mie effects, limiting the HE efficiencies for the long and large NRs. These properties of the L-plasmon relate to all kinds of NRs (Au, Ag, and Au-Ag). We also consider the generation of the interband d-holes in Au and Ag, since the involvement of the d-band is crucial for the energetic properties of UV plasmons. The proposed formalism is an important development for the description of bi-metallic (or tri-metallic, or more complex) nanostructures, and it paves the way to the efficient application of the plasmonic HEs and hot holes in sensing, nanotechnology, photocatalysis, and electrophotochemistry.

cond-mat.mes-hall↗

arXiv2023

Self-assembled physical unclonable function labels based on plasmonic coupling

Counterfeiting threatens human health, social equity, national security and global and local economies. Hardware-based cryptography that exploits physical unclonable functions (PUFs) provides the means for secure identification and authentication of products. While optical PUFs are among the hardest to replicate, they suffer from low encoding capacity and often complex and expensive read-out. Here we report PUF labels with nanoscale features and optical responses that arise from the guided self-assembly of plasmonic nanoparticles. Nanosphere lithography combined with DNA origami placement are used to create tightly packed randomised nanoparticle assemblies. Nanoscale variations within these assemblies define the scattering color of the individual spots that are arranged in a hexagonal lattice with spacing down to the optical resolution limit. Due to the nanoscale dimensions, the intrinsic randomness of the particle assemblies and their resulting optical responses, our PUFs are virtually impossible to replicate while they can be read-out with economical 3D-printed hardware.

cond-mat.mtrl-sci↗

arXiv2023

Diamond-lattice photonic crystals assembled from DNA origami

Colloidal self-assembly allows rational design of structures on the micrometer and submicrometer scale. One architecture that can generate complete 3D photonic band gaps is the diamond cubic lattice, which has remained difficult to realize at length scales comparable to the wavelength of visible or ultraviolet light. Here, we demonstrate three-dimensional photonic crystals self-assembled from DNA origami that act as precisely programmable patchy colloids. Our DNA-based nanoscale tetrapods crystallize into a rod-connected diamond cubic lattice with a periodicity of 170 nm. This structure serves as a scaffold for atomic layer deposition of high refractive index materials such as TiO$_2$, yielding a tunable photonic band gap in the near-ultraviolet.

physics.app-ph↗

arXiv2023

Controlling the size and adhesion of DNA droplets using surface-active DNA molecules

Liquid droplets of biomolecules serve as organizers of the cellular interior and are of interest in biosensing and biomaterials applications. Here, we investigate means to tune the interfacial properties of a model biomolecular liquid consisting of multi-armed DNA 'nanostar' particles. We find that long DNA molecules that have binding affinity for the nanostars are preferentially enriched on the interface of nanostar droplets, thus acting as surfactants. Fluorescent measurements indicate that, in certain conditions, the interfacial density of the surfactant is around 20 per square micron, indicative of a sparse brush-like structure of the long, polymeric DNA. Increasing surfactant concentration leads to decreased droplet size, down to the sub-micron scale, consistent with arrest of droplet coalescence by the disjoining pressure created by the brush-like surfactant layer. Added DNA surfactant also keeps droplets from adhering to both hydrophobic and hydrophilic solid surfaces, apparently due to this same disjoining effect of the surfactant layer. We thus demonstrate control of the size and adhesive properties of droplets of a biomolecular liquid, with implications for basic biophysical understanding of such droplets, as well as for their applied use.

cond-mat.soft↗

arXiv2021

On the origin of chirality in plasmonic meta-molecules

Chirality is a fundamental feature in all domains of nature, ranging from particle physics over electromagnetism to chemistry and biology. Chiral objects lack a mirror plane and inversion symmetry and therefore cannot be spatially aligned with their mirrored counterpart, their enantiomer. Both natural molecules and artificial chiral nanostructures can be characterized by their light-matter interaction, which is reflected in circular dichroism (CD). Using DNA origami, we assemble model meta-molecules from multiple plasmonic nanoparticles, representing meta-atoms accurately positioned in space. This allows us to reconstruct piece by piece the impact of varying macromolecular geometries on their surrounding optical near fields. Next to the emergence of CD signatures in the instance that we architect a third dimension, we design and implement sign flipping signals through addition or removal of single particles in the artificial molecules. Our data and theoretical modelling reveal the hitherto unrecognized phenomenon of chiral plasmonic-dielectric coupling, explaining the intricate electromagnetic interactions within hybrid DNA-based plasmonic nanostructures.

physics.optics↗

arXiv2021

DNA-Assembled Advanced Plasmonic Architectures

The interaction between light and matter can be controlled efficiently by structuring materials at a length scale shorter than the wavelength of interest. With the goal to build optical devices that operate at the nanoscale, plasmonics has established itself as a discipline, where near-field effects of electromagnetic waves created in the vicinity of metallic surfaces can give rise to a variety of novel phenomena and fascinating applications. As research on plasmonics has emerged from the optics and solid-state communities, most laboratories employ top-down lithography to implement their nanophotonic designs. In this review, we discuss the recent, successful efforts of employing self-assembled DNA nanostructures as scaffolds for creating advanced plasmonic architectures. DNA self-assembly exploits the base-pairing specificity of nucleic acid sequences and allows for the nanometer-precise organization of organic molecules but also for the arrangement of inorganic particles in space. Bottom-up self-assembly thus bypasses many of the limitations of conventional fabrication methods. As a consequence, powerful tools such as DNA origami have pushed the boundaries of nanophotonics and new ways of thinking about plasmonic designs are on the rise.

physics.optics↗

arXiv2020

Long- and Short-Ranged Chiral Interactions in DNA Assembled Plasmonic Chains

Molecular chirality plays a crucial role in innumerable biological processes. The chirality of a molecule can typically be identified by its characteristic optical response, the circular dichroism (CD). CD signals have thus long been used to identify the state of molecules or to follow dynamic protein configurations. In recent years, the focus has moved towards plasmonic nanostructures, as they show potential for applications ranging from pathogen sensing to novel optical materials. The plasmonic coupling of the individual elements of such chiral metallic structures is a crucial prerequisite to obtain sizeable CD signals. We here identified and implemented various coupling entities - chiral and achiral - to obtain chiral transfer over distances close to 100 nm. The coupling is realized by an achiral nanosphere situated between a pair of gold nanorods that are arranged far apart but in a chiral fashion. We synthesized these structures with nanometer precision using DNA origami and obtained sample homogeneity that allowed us to directly demonstrate efficient chiral energy transfer between the distant nanorods. The transmitter particle causes a strong enhancement in amplitude of the CD response, the emergence of an additional chiral feature at the resonance frequency of the nanosphere, and a redshift of the longitudinal plasmonic resonance frequency of the nanorods. Numerical simulations closely match our experimental observations and give insights in the intricate behavior of chiral optical fields and the transfer of plasmons in complex architectures.

physics.optics↗

arXiv2019

Circular Dichroism of Chiral Molecules in DNA- Assembled Plasmonic Hotspots

The chiral state of a molecule plays a crucial role in molecular recognition and biochemical reactions. Because of this and owing to the fact that most modern drugs are chiral, the sensitive and reliable detection of the chirality of molecules is of great interest to drug development. The majority of naturally occurring biomolecules exhibit circular dichroism (CD) in the UV-range. Theoretical studies and several experiments have demonstrated that this UV-CD can be transferred into the plasmonic frequency domain when metal surfaces and chiral biomolecules are in close proximity. Here, we demonstrate that the CD transfer effect can be drastically enhanced by placing chiral molecules, here double-stranded DNA, inside a plasmonic hotspot. By using different particle types (gold, silver, spheres and rods) and by exploiting the versatility of DNA origami we were able to systematically study the impact of varying particle distances on the CD transfer efficiency and to demonstrate CD transfer over the whole optical spectrum down to the near infrared. For this purpose, nanorods were also placed upright on our DNA origami sheets, this way forming strong optical antennas. Theoretical models, demonstrating the intricate relationships between molecular chirality and achiral electric fields, support our experimental findings.

cond-mat.mes-hall↗

arXiv2019

Chiral plasmonic nanocrystals for generation of hot electrons: towards polarization-sensitive photochemistry

The use of biomaterials - with techniques such as DNA-directed assembly or bio-directed synthesis - can surpass top-down fabrication techniques in creating plasmonic superstructures, in terms of spatial resolution, range of functionality and fabrication speed. Particularly, by enabling a very precise placement of nanoparticles in a bio-assembled complex or a controlled bio-directed shaping of single nanoparticles, plasmonic nanocrystals can show remarkably strong circular dichroism (CD) signals. Here we show that chiral bio-plasmonic assemblies and nanocrystals can enable polarization-sensitive photochemistry based on the generation of energetic (hot) electrons. It is now established that hot plasmonic electrons can induce surface photochemistry or even reshape plasmonic nanocrystals. Here we show that merging chiral plasmonic nanocrystal systems and the hot-election generation effect offers unique possibilities in photochemistry - such as polarization-sensitive photochemistry promoting nonchiral molecular reactions, chiral photo-induced growth of a colloid at the atomic level and chiral photochemical destruction of chiral nanocrystals. Regarding practical applications, our study suggests interesting opportunities in polarization-sensitive photochemistry, chiral recognition or separation, and in promoting chiral crystal growth at the nanoscale.

physics.app-ph↗

arXiv2017

3D DNA origami crystals

Engineering shape and interactions of nanoscopic building blocks allows for the assembly of rationally designed macroscopic three-dimensional (3D) materials with spatial accuracy inaccessible to top-down fabrication methods. Owing to its sequence-specific interaction, DNA is often used as selective binder to connect metallic nanoparticles into highly ordered lattices. Moreover, 3D crystals assembled entirely from DNA have been proposed and implemented with the declared goal to arrange guest molecules in predefined lattices. This requires design schemes that provide high rigidity and sufficiently large open guest space. We here present a DNA origami-based tensegrity triangle structure that assembles into a 3D rhombohedral crystalline lattice. We site-specifically place 10 nm and 20 nm gold particles within the lattice, demonstrating that our crystals are spacious enough to host e.g. ribosome-sized macromolecules. We validate the accurate assembly of the DNA origami lattice itself as well as the precise incorporation of gold particles by electron microscopy and small angle X-ray scattering (SAXS) experiments. Our results show that it is possible to create DNA building blocks that assemble into lattices with customized geometry. Site-specific hosting of nano objects in the transparent DNA lattice sets the stage for metamaterial and structural biology applications.

cond-mat.soft↗

arXiv2017

Plasmon-Exciton Coupling Using DNA Templates

Coherent energy exchange between plasmons and excitons is a phenomenon that arises in the strong coupling regime resulting in distinct hybrid states. The DNA-origami technique provides an ideal framework to custom-tune plasmon-exciton nanostructures. By employing this well controlled self-assembly process, we realized hybrid states by precisely positioning metallic nanoparticles in a defined spatial arrangement with fixed nanometer-sized interparticle spacing. Varying the nanoparticle diameter between 30 nm and 60 nm while keeping their separation distance constant allowed us to precisely adjust the plasmon resonance of the structure to accurately match the energy frequency of a J-aggregate exciton. With this system we obtained strong plasmon-exciton coupling and studied far-field scattering at the single-structure level. The individual structures displayed normal mode splitting up to 170 meV. The plasmon tunability and the strong field confinement attained with nanodimers on DNA-origami renders an ideal tool to bottom-up assembly plasmon-exciton systems operating at room temperature.

cond-mat.mes-hall↗

arXiv2017

Hot spot-mediated non-dissipative and ultrafast plasmon passage

Plasmonic nanoparticles hold great promise as photon handling elements and as channels for coherent transfer of energy and information in future all-optical computing devices. Coherent energy oscillations between two spatially separated plasmonic entities via a virtual middle state exemplify electron-based population transfer, but their realization requires precise nanoscale positioning of heterogeneous particles. Here, we show the assembly and optical analysis of a triple particle system consisting of two gold nanoparticles with an inter-spaced silver island. We observe strong plasmonic coupling between the spatially separated gold particles mediated by the connecting silver particle with almost no dissipation of energy. As the excitation energy of the silver island exceeds that of the gold particles, only quasi-occupation of the silver transfer channel is possible. We describe this effect both with exact classical electrodynamic modeling and qualitative quantum-mechanical calculations. We identify the formation of strong hot spots between all particles as the main mechanism for the loss-less coupling and thus coherent ultra-fast energy transfer between the remote partners. Our findings could prove useful for quantum gate operations, but also for classical charge and information transfer processes.

cond-mat.mes-hall↗

arXiv2011

DNA-based Self-Assembly of Chiral Plasmonic Nanostructures with Tailored Optical Response

Surface plasmon resonances generated in metallic nanostructures can be utilized to tailor electromagnetic fields. The precise spatial arrangement of such structures can result in surprising optical properties that are not found in any naturally occurring material. Here, the designed activity emerges from collective effects of singular components equipped with limited individual functionality. Top-down fabrication of plasmonic materials with a predesigned optical response in the visible range by conventional lithographic methods has remained challenging due to their limited resolution, the complexity of scaling, and the difficulty to extend these techniques to three-dimensional architectures. Molecular self-assembly provides an alternative route to create such materials which is not bound by the above limitations. We demonstrate how the DNA origami method can be used to produce plasmonic materials with a tailored optical response at visible wavelengths. Harnessing the assembly power of 3D DNA origami, we arranged metal nanoparticles with a spatial accuracy of 2 nm into nanoscale helices. The helical structures assemble in solution in a massively parallel fashion and with near quantitative yields. As a designed optical response, we generated giant circular dichroism and optical rotary dispersion in the visible range that originates from the collective plasmon-plasmon interactions within the nanohelices. We also show that the optical response can be tuned through the visible spectrum by changing the composition of the metal nanoparticles. The observed effects are independent of the direction of the incident light and can be switched by design between left- and right-handed orientation. Our work demonstrates the production of complex bulk materials from precisely designed nanoscopic assemblies and highlights the potential of DNA self-assembly for the fabrication of plasmonic nanostructures.

cond-mat.mes-hall↗