The availability of metamaterials with properties that can be actively tuned is crucial for the future development of various metamaterial-based technologies. Here we show that by using silver nanoparticles equipped with a thermally responsive organic coating a metamaterial is obtained with reversibly switchable properties. The material investigated exhibits dynamic self-assembly resulting from temperature-dependent changes of organic coating shape, which translates to a switchable spatial distribution of the silver nanoparticles. This in turn strongly influences the optical properties of the entire material. The measured optical characteristics of the material are in excellent agreement with theoretical calculations, which allow us to use the latter to predict a dynamically tunable epsilon-near-zero behaviour of the metamaterial. The suggested methodology opens new routes for tunable metamaterials that operate in the visible region and will enable various applications for soft-matter-based optical devices.

On the GO: The basal plane allylic alcohol functionality of graphite oxide (GO) can be converted into N,N-dimethylamide groups through an Eschenmoser–Claisen sigmatropic rearrangement by using N,N-dimethylacetamide dimethyl acetal. Subsequent saponification of these groups affords the carboxylic acids (see picture), which, when deprotonated, electrostatically stabilize the graphene sheets in an aqueous environment.

The availability of helical assemblies of plasmonic nanoparticles with precisely controlled and tunable structures can play a key role in the future development of chiral plasmonics and metamaterials. Here, a strategy to efficiently yield helical structures based on the cooperative interactions of liquid crystals and gold nanoparticles in thin films is developed. These nanocomposites exhibit exceptional long‐range hierarchical order across length scales, which results from the growth mechanism of nanoparticle‐coated twisted nanoribbons and their ability to form organized bundles. The helical assembly formation is governed by the presence of rationally functionalized nanoparticles. Importantly, the thickness of the achieved nanocomposites can be reversibly reconfigured owing to the polymorphic nature of the liquid crystal. The versatility of the proposed approach is demonstrated by preparing helices assembled from nanoparticles of different geometries and dimensions (spherical and rod‐like). The described strategy may become an enabling technology for structuring nanoparticle assemblies with high precision and fabricating optically active materials.

Thin films sustaining plasmonic circular dichroism (PCD) have acquired high scientific relevance and a great potential for applications. While most efforts in PCD thin film structures focus on lithographically fabricated static metasurfaces, the bottom‐up fabrication of active chiral plasmonic films constitutes an alternative approach. Herein, the preparation of PCD thin films by melting and freezing a mixture of liquid crystal (LC), a chiral dopant, and gold nanoparticles (Au NPs), serving as helical matrix, symmetry breaking inducer, and plasmonic component, respectively is reported. UV–vis and circular dichroism spectroscopies, as well as theoretical modeling are used to disclose the interactions among thin film components, toward maximizing the PCD dissymmetry factor (g‐factor). Variation of substrate temperature affords reversible off/on switching of the chiroptical response. The soft nature of LC matrix enables patterning of the films via a thermal nanoimprinting method, using a polydimethylsiloxane mold for transfer‐printing onto a flexible substrate, leading to stretchable PCD films. The PCD wavelengths can be readily tuned by varying the geometry of the Au NPs. This work provides an efficient technique to produce PCD thin films with active plasmonic properties and mechanical tunability.

Mirror symmetry breaking in materials is a fascinating phenomenon that has practical implications for various optoelectronic technologies. Chiral plasmonic materials are particularly appealing due to their strong and specific interactions with light. In this work we broaden the portfolio of available strategies toward the preparation of chiral plasmonic assemblies, by applying the principles of chirality synchronization - a phenomenon known for small molecules, which results in the formation of chiral domains from transiently chiral molecules. We report the controlled co-crystallization of 23 nm gold nanoparticles and liquid crystal molecules yielding domains made of highly ordered, helical nanofibers, preferentially twisted to the right or to the left within each domain. We confirmed that such micrometer size domains exhibit strong, far-field circular dichroism (CD) signals, even though the bulk material is racemic. We further highlight the potential of the proposed approach to realize chiral plasmonic thin films by using a mechanical chirality discrimination method. Towards this end, we developed a rapid CD imaging technique based on the use of polarized light optical microscopy (POM), which enabled probing the CD-signal with micrometer-scale resolution, despite of linear dichroism and birefringence in the sample. The developed methodology allows us to extend intrinsically local effects of chiral synchronization to the macro scale, thereby broadening the available tools for chirality manipulation in chiral plasmonic systems.