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Engineering the nucleation and growth of plasmonic metals (Ag and Au) on their pre-existing seeds is expected to produce nanostructures with unconventional morphologies and plasmonic properties that may find unique applications in sensing, catalysis, and broadband energy harvesting. Typical seed-mediated growth processes take advantage of the perfect lattice match between the deposited metal and seeds to induce conformal coating, leading to either simple size increases (e.g., Au on Au) or the formation of core-shell structures (e.g., Ag on Au) with limited morphology change. In this work, we show that the introduction of a thin layer of metal with considerable lattice mismatch can effectively induce the nucleation of well-defined Au islands on Au nanocrystal seeds. By controlling the interfacial energy between the seed and the deposited material, the oxidative ripening, and the surface diffusion of metal precursors, we can regulate the number of islands on the seeds and produce complex Au nanostructures with morphologies tunable from core-satellites to tetramers, trimers, and dimers. This surface engineering strategy is of great significance in nanomaterial synthesis as it is general and can be used to create secondary structures of many other nanocrystals in a controllable manner.

The fast and reversible switching of plasmonic color holds great promise for many applications, while its realization has been mainly limited to solution phases, achieving solid-state plasmonic color-switching has remained a significant challenge owing to the lack of strategies in dynamically controlling the nanoparticle separation and their plasmonic coupling. Herein, we report a novel strategy to fabricate plasmonic color-switchable silver nanoparticle (AgNP) films. Using poly(acrylic acid) (PAA) as the capping ligand and sodium borate as the salt, the borate hydrolyzes rapidly in response to moisture and produces OH- ions, which subsequently deprotonate the PAA on AgNPs, change the surface charge, and enable reversible tuning of the plasmonic coupling among adjacent AgNPs to exhibit plasmonic color-switching. Such plasmonic films can be printed as high-resolution invisible patterns, which can be readily revealed with high contrast by exposure to trace amounts of water vapor.

Herein, we show that copper nanostructures, if made anisotropic, can exhibit strong surface plasmon resonance comparable to that of gold and silver counterparts in the near-infrared spectrum. Further, we demonstrate that a robust confined seeded growth strategy allows the production of high-quality samples with excellent control over their size, morphology, and plasmon resonance frequency. As an example, copper nanorods (CuNRs) are successfully grown in a limited space of preformed rod-shaped polymer nanocapsules, thereby avoiding the complex nucleation kinetics involved in the conventional synthesis. The method is unique in that it enables the flexible control and fine-tuning of the aspect ratio and the plasmonic resonance. We also show the high efficiency and stability of the as-synthesized CuNRs in photothermal conversion and demonstrate their incorporation into nanocomposite polymer films that can be used as active components for constructing light-responsive actuators and microrobots.

Out of the frame: A marker study using gold frames was designed to reveal that silver nanoplates undergo a shape transition during their seeded growth from triangular to circular to hexagonal plates before ultimately returning to triangular structures with an orientation 180° relative to that of the original triangular seeds (see picture, the original gold triangular frame is visible at the center of the silver nanoplate).

Dieser Aufsatz fasst jungste Entwicklung auf dem Gebiet der responsiven photonischen Kristalle zusammen, einschlieslich Design-, Fertigungs- und Anwendungsstrategien, z. B. als optische Schalter oder chemische und biologische Sensoren. Eine Reihe von Fertigungsmethoden fur responsive photonische Strukturen ist heute verfugbar, die hauptsachlich auf Selbstorganisationsprozessen beruhen. Gegenuber Mikrofertigungsverfahren besitzen diese Ansatze die Vorteile geringerer Prozesskosten und einer besseren Produktionseffizienz, es gibt aber noch betrachtliche Herausforderungen zu bewaltigen. Einige Techniken wie Schleuderbeschichtung, magnetische Aggregation und durchflussinduzierte Selbstorganisation erweisen sich hier als vielversprechend. Entscheidende Hinweise fur den Entwurf neuer, verbesserter Systeme konnte das Vorbild naturlicher photonischer Strukturen bieten.

The development of more efficient and stable catalysts hasbeen an increasingly important goal for chemists andmaterials scientists for both economic and environmentalreasons. Much attention has been paid recently to nano-particlesoftransitionmetals,particularlynoblemetals,asaresult of significant progress in synthetic methods forcontrollingtheircomposition,size,andshape.Thisdevelop-ment should lead to the design of catalysts with superiorperformance that take advantage of nanoparticles highsurface-to-volume ratio and their shape-dependent surfacestructure.

tence of a large number of silicate species and their rich chemical interactions makes the dissolution and growth of silica challenging to study. However, this complexity also provides enormous opportunities for the development of materials with new structures and functionalities. For example, systematic investigation of the dissolution and formation of silica nanoparticles has made it possible to control the nucleation and growth, and subsequently the crystal size and shape, of zeolite materials. [4–6] Herein, we report that amorphous silica colloids, when dispersed in an aqueous solution of NaBH4, undergo a spontaneous morphology change from solid to hollow spheres. Concurrent but separate coredissolution and shell-growth processes appear to be responsible to the formation of the hollow structures. Besides the interesting fundamental aspects of this spontaneous process, this work also provides an effective self-templated route for the preparation of hollow silica nanostructures, which may find immediate applications in fields such as catalysis and drug delivery. [7–12] Since silica can coat many nanostructures through simple sol–gel processes, our discovery also allows convenient transformation of core–shell particles into yolk– shell structures, which are promising for use as nanoscale reactors and controlled-release vehicles. Compared to widely adopted methods using polymer beads and micelle and

Controlling the shape of nanocrystals is critical to modernmaterials chemistry because the intrinsic properties of mostnanomaterials are strongly dependent on their shape.