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.
Self‐assembly concepts for colloidal metasurfaces via incremental increase in the number of particles are reviewed here: from colloidal particles as building blocks, to unit cells from few colloids dominated by near‐field coupling, over 1D plasmonic “polymers,” to collective coupling within particle clusters, and 2D plasmonic lattices with long‐distance coupling.
Polymer brushes, consisting of densely end-tethered polymers to a surface, can exhibit rapid and sharp conformational transitions due to specific stimuli, which offer intriguing possibilities for ...surface-based sensing of the stimuli. The key toward unlocking these possibilities is the development of methods to readily transduce signals from polymer conformational changes. Herein, we report on single-fluorophore integrated ultrathin (<40 nm) polymer brush surfaces that exhibit changing fluorescence properties based on polymer conformation. The basis of our methods is the change in occupied volume as the polymer brush undergoes a collapse transition, which enhances the effective concentration and aggregation of the integrated fluorophores, leading to a self-quenching of the fluorophores’ fluorescence and thereby reduced fluorescence lifetimes. By using fluorescence lifetime imaging microscopy, we reveal spatial details on polymer brush conformational transitions across complex interfaces, including at the air–water–solid interface and at the interface of immiscible liquids that solvate the surface. Furthermore, our method identifies the swelling of polymer brushes from outside of a direct droplet (i.e., the polymer phase with vapor above), which is controlled by humidity. These solvation-sensitive surfaces offer a strong potential for surface-based sensing of stimuli-induced phase transitions of polymer brushes with spatially resolved output in high resolution.
Thermally processable soft material networks with adjustable mechanical properties made from very low molar mass α,ω-dithiol functionalized ABA triblock co-oligomers (α,ω-dithiol ...oligo(isoprene-b-styrene-b-isoprene) (TISIT)) using AgNP as thermally reversible cross-linking points are highlighted in the present work. Liquid TISIT oligomers were synthesized by sequential anionic polymerization and subsequently cross-linked with AgNP. Low molar masses (4200–4800 g mol–1) were engaged, assuring disordered microstructures and therefore, low viscosities at elevated temperatures. Smooth films with homogeneous nanoparticle distributions of the resulting quasi-segmented soft material networks (TISIT@AgNP) were made by heat pressing. The interplay of styrene and AgNP as the structure-supplying portions in TISIT@AgNP samples facilitates access to materials with tensile strengths up to 5.58 MPa, toughness up to 13.3 MN mm–2, and tensile moduli up to 80.1 MPa at room temperature and strongly decreased elasticity and viscosity at elevated temperatures, even below the glass transition temperature of polystyrene.
We present a fluorescent emitter (rhodamine B) coupled to a dielectric or metallic interface as well as a metallic cavity to study their radiative decay processes. Supported by finite-difference ...time-domain (FDTD) simulations, we correlate the non-radiative and radiative decay rates with the absorption and scattering cross section efficiencies, respectively. On a single particle level, we use atomic force microscopy (AFM), scanning electron microscopy (SEM), scattering spectroscopy, fluorescence life time imaging (FLIM) and time-correlated single photon counting (TCSPC) to evaluate the enhanced fluorescence decay at the same location. With this study, we show a colloidal gain material, which can be integrated into lattices using existing directed self-assembled methods to study their coherent energy transfer.
Many common CPU architectures provide simultaneous multithreading (SMT). The operating system sees multiple logical CPU cores per physical CPU core and can schedule several processes to one physical ...CPU core. This overbooking of physical cores enables a better usage of parallel pipelines and doubled components within a CPU core. On systems with several applications running in parallel, such as batch jobs on worker nodes, the usage of SMT can increase the overall performance. In high energy physics (HEP) batch/Grid jobs are accounted for in units of single-core jobs. One single-core job is designed to utilize one logical CPU core fully. As a result, Grid sites often configure their worker nodes to provide as many single-core slots as physical or logical CPU cores. However, due to memory and disk space constraints, not all logical CPU cores can be used. Therefore, it can be useful to configure more single-core slots than physical CPU cores but fewer than logical CPU cores per worker node. We have extensively used and studied this strategy at the GridKa Tier 1 center. In this contribution, we show benchmark results for different overbooking factors of physical cores on various CPU models for different HEP workflows and Benchmarks.
Computing resource needs are expected to increase drastically in the future. The HEP experiments ATLAS and CMS foresee an increase of a factor of 5-10 in the volume of recorded data in the upcoming ...years. The current infrastructure, namely the WLCG, is not sufficient to meet the demands in terms of computing and storage resources.
The usage of non HEP specific resources is one way to reduce this shortage. However, using them comes at a cost: First, with multiple of such resources at hand, it gets more and more diffcult for the single user, as each resource normally requires its own authentication and has its own way of accessing it. Second, as they are not specifically designed for HEP workflows, they might lack dedicated software or other necessary services.
Allocating the resources at the different providers can be done by COBalD/TARDIS, developed at KIT. The resource manager integrates resources on demand into one overlay batch system, providing the user with a single point of entry. The software and services, needed for the communities workflows, are transparently served through containers.
With this, an HPC cluster at RWTH Aachen University is dynamically and transparently integrated into a Tier 2 WLCG resource, virtually doubling its computing capacities.
Demand for computing resources in high energy physics (HEP) shows a highly dynamic behavior, while the provided resources by the Worldwide LHC Computing Grid (WLCG) remains static. It has become ...evident that opportunistic resources such as High Performance Computing (HPC) centers and commercial clouds are well suited to cover peak loads. However, the utilization of these resources gives rise to new levels of complexity, e.g. resources need to be managed highly dynamically and HEP applications require a very specific software environment usually not provided at opportunistic resources. Furthermore, aspects to consider are limitations in network bandwidth causing I/O-intensive workflows to run inefficiently.
The key component to dynamically run HEP applications on opportunistic resources is the utilization of modern container and virtualization technologies. Based on these technologies, the Karlsruhe Institute of Technology (KIT) has developed ROCED, a resource manager to dynamically integrate and manage a variety of opportunistic resources. In combination with ROCED, HTCondor batch system acts as a powerful single entry point to all available computing resources, leading to a seamless and transparent integration of opportunistic resources into HEP computing.
KIT is currently improving the resource management and job scheduling by focusing on I/O requirements of individual workflows, available network bandwidth as well as scalability. For these reasons, we are currently developing a new resource manager, called TARDIS. In this paper, we give an overview of the utilized technologies, the dynamic management, and integration of resources as well as the status of the I/O-based resource and job scheduling.
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