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Hybrid metallic nanoparticles (NPs) encapsulated in oxide shells are currently intensely studied for plasmonic applications in sensing, medicine, catalysis, and photovoltaics. Here, a method for the synthesis of Au@Ag@SiO2 cubes with a uniform silica shell of variable and adjustable thickness in the nanometer range is introduced and their excellent, highly reproducible, and tunable optical response is demonstrated. Varying the silica shell thickness, the excitation energies of the single NP plasmon modes can be tuned in a broad spectral range between 2.55 and 3.25 eV. Most importantly, a strong coherent coupling of the surface plasmons is revealed at the silver–silica interface with Mie resonances at the silica–vacuum interface leading to a significant field enhancement at the encapsulated NP surface in the range of 100% at shell thicknesses t ≃ 20 nm. Consequently, the synthesis method and the field enhancement open pathways to a widespread use of silver NPs in plasmonic applications including photonic crystals and may be transferred to other non‐precious metals. [ABSTRACT FROM AUTHOR]

The growth of crystalline nanoparticles (NPs) generally involves three processes: nucleation, growth, and shape evolution. Among them, the shape evolution is less understood, despite the importance of morphology for NP properties. Here, we propose a symmetry‐based kinematic theory (SBKT) based on classical growth theories to illustrate the process. Based on the crystal lattice, nucleus (or seed) symmetry, and the preferential growth directions under the experimental conditions, the SBKT can illustrate the growth trajectories. The theory accommodates the conventional criteria of the major existing theories for crystal growth and provides tools to better understand the symmetry‐breaking process during the growth of anisotropic structures. Furthermore, complex dendritic growth is theoretically and experimentally demonstrated. Thus, it provides a framework to explain the shape evolution, and extends the morphogenesis prediction to cases, which cannot be treated by other theories. [ABSTRACT FROM AUTHOR]

Das Wachstum von kristallinen Nanopartikeln (NP) umfasst im Allgemeinen drei Prozesse: Keimbildung, Wachstum und die Entwicklung der Form. Von diesen Prozessen ist die Formentwicklung trotz der Bedeutung der Morphologie für die Eigenschaften der NP am wenigsten verstanden. Hier beschreiben wir eine symmetriebasierte kinematische Theorie (SBKT) die auf klassischen Wachstumstheorien basiert, um den Prozess zu veranschaulichen. Auf Grundlage des Kristallgitters, der Keim‐ (oder Kern‐) Symmetrie und der bevorzugten Wachstumsrichtungen unter den experimentellen Bedingungen kann die SBKT die Wachstumstrajektorien veranschaulichen. Die Theorie erfüllt die konventionellen Kriterien der wichtigsten bestehenden Theorien für das Kristallwachstum und bietet Werkzeuge zum besseren Verständnis des Symmetriebrechens während des Wachstums anisotroper Strukturen. Darüber hinaus wird das komplexe dendritische Wachstum sowohl theoretisch als auch experimentell nachgewiesen. Damit bietet sie einen Ansatz zur Erklärung der Formentwicklung und erweitert die Vorhersage der Morphogenese auf Fälle, die von anderen Theorien nicht erfasst werden können. [ABSTRACT FROM AUTHOR]

Post‐polymerization modification provides an elegant way to introduce chemical functionalities onto macromolecules to produce tailor‐made materials with superior properties. This concept was adapted to well‐defined block copolymers of the poly(2‐oxazoline) family and demonstrated the large potential of these macromolecules as universal toolkit for numerous applications. Triblock copolymers with separated water‐soluble, alkyne‐ and alkene‐containing segments were synthesized and orthogonally modified with various low‐molecular weight functional molecules by copper(I)‐catalyzed azide‐alkyne cycloaddition (CuAAC) and thiol‐ene (TE) click reactions, respectively. Representative toolkit polymers were used for the synthesis of gold, iron oxide and silica nanoparticles. [ABSTRACT FROM AUTHOR]