281 research outputs found
Soft self-assembly of Weyl materials for light and sound
Soft materials can self-assemble into highly structured phases which
replicate at the mesoscopic scale the symmetry of atomic crystals. As such,
they offer an unparalleled platform to design mesostructured materials for
light and sound. Here, we present a bottom-up approach based on self-assembly
to engineer three-dimensional photonic and phononic crystals with topologically
protected Weyl points. In addition to angular and frequency selectivity of
their bulk optical response, Weyl materials are endowed with topological
surface states, which allows for the existence of one-way channels even in the
presence of time-reversal invariance. Using a combination of group-theoretical
methods and numerical simulations, we identify the general symmetry constraints
that a self-assembled structure has to satisfy in order to host Weyl points,
and describe how to achieve such constraints using a symmetry-driven pipeline
for self-assembled material design and discovery. We illustrate our general
approach using block copolymer self-assembly as a model system.Comment: published version, SI are available as ancillary files, code and data
are available on Zenodo at https://doi.org/10.5281/zenodo.1182581, PNAS
(2018
Two-dimensional superstructures of silica cages
Despite extensive studies on mesoporous silica since the early 1990s, the synthesis of two-dimensional (2D) silica nanostructures remains challenging. Here, mesoporous silica is synthesized at an interface between two immiscible solvents under conditions leading to the formation of 2D superstructures of silica cages, the thinnest mesoporous silica films synthesized to date. Orientational correlations between cage units increase with increasing layer number controlled via pH, while swelling with oil and mixed surfactants increase micelle size dispersity, leading to complex clathrate type structures in multilayer superstructures. The results suggest that a three-dimensional (3D) crystallographic registry within cage-like superstructures emerges as a result of the concerted 3D co-assembly of the organic and inorganic components. Mesoporous 2D superstructures can be fabricated over macroscopic film dimensions and stacked on top of each other. The realization of previously inaccessible mesoporous silica heterostructures with separation or catalytic properties unachievable via conventional bulk syntheses is envisioned
Fluorescent silica manoparticles with well-separated intensity distributions from batch reactions
Silica chemistry provides pathways to uniquely tunable nanoparticle platforms for biological imaging. It has been a long-standing problem to synthesize fluorescent silica nanoparticles (SNPs) in batch reactions with high and low fluorescence intensity levels for reliable use as an intensity barcode, which would greatly increase the number of molecular species that could be tagged intracellularly and simultaneously observed in conventional fluorescence microscopy. Here, employing an amino-acid catalyzed growth, highly fluorescent SNP probes were synthesized with sizes <40 nm and well-separated intensity distributions, as mapped by single-particle imaging techniques. A seeded growth approach was used to minimize the rate of secondary particle formation. Organic fluorescent dye affinity for the SNP during shell growth was tuned using specifics of the organosilane linker chemistry. This work highlights design considerations in the development of fluorescent probes with well-separated intensity distributions synthesized in batch reactions for single-particle imaging and sensing applications, where heterogeneities across the nanoparticle ensemble are critical factors in probe performance
Fluorescent silica manoparticles with well-separated intensity distributions from batch reactions
Silica chemistry provides pathways to uniquely tunable nanoparticle platforms for biological imaging. It has been a long-standing problem to synthesize fluorescent silica nanoparticles (SNPs) in batch reactions with high and low fluorescence intensity levels for reliable use as an intensity barcode, which would greatly increase the number of molecular species that could be tagged intracellularly and simultaneously observed in conventional fluorescence microscopy. Here, employing an amino-acid catalyzed growth, highly fluorescent SNP probes were synthesized with sizes <40 nm and well-separated intensity distributions, as mapped by single-particle imaging techniques. A seeded growth approach was used to minimize the rate of secondary particle formation. Organic fluorescent dye affinity for the SNP during shell growth was tuned using specifics of the organosilane linker chemistry. This work highlights design considerations in the development of fluorescent probes with well-separated intensity distributions synthesized in batch reactions for single-particle imaging and sensing applications, where heterogeneities across the nanoparticle ensemble are critical factors in probe performance
Berechnung und Regionalisierung der Kohlenstoffvorräte rheinland-pfälzischer Böden
Böden sind weltweit der größte terrestrische Speicher für organischen Kohlenstoff. Im Boden ist organischer Kohlenstoff von grundlegender Bedeutung für die Nährstoffversorgung von Pflanzen, die Gefügeeigenschaften, das Wasserspeichervermögen, die biologische Vielfalt und die Regulierung des globalen Kohlenstoffkreislaufs. Im Rahmen des Landesprojekts Klima- und Landschaftswandel in Rheinland-Pfalz (KlimLandRP) wurden die Kohlenstoffvorräte rheinland-pfälzischer Böden berechnet und auf Basis der Bodenübersichtskarte 1: 200.000 (BÜK 200) regionalisiert
Mesoscopic structure prediction of nanoparticle assembly and coassembly: Theoretical foundation
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Research Data Supporting "Gyroid Optical Metamaterials: Calculating the Effective Permittivity of Multidomain Samples"
Data Supporting Publication "Gyroid Optical Metamaterials: Calculating the Effective Permittivity of Multidomain Samples"Swiss National Science Foundation, National Center of Competence in Research Bio-Inspired Materials, [200021_163220 and PZ00P2_168223], EPSRC [Cambridge NanoDTC EP/G037221/1, EP/L027151/1, and EP/G060649/1], ERC [LINASS 320503], European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie [706329], Adolphe Merkle Foundatio
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