Gold and Silver Dichroic Nanocomposite in the Quest for 3D Printing the Lycurgus Cup

The Lycurgus cup is worldwide admired in particular because of its fascinating dichroic property. The cup presents a green colour when the observer and the light source are on the same side (reflection), and a deep red colour when the observer and the light source are at opposite sides (transmission). This peculiar effect, which has perplexed scientists for centuries, was discovered to be due to the presence of nanoparticles in the glass. In particular, to two different metallic nanoparticles: silver nanoparticles (AgNP) and gold nanoparticles (AuNP). Here we show how dichroic silver nanoparticles and gold nanoparticles can be embedded in a 3D printable material in order to reproduce the same dichroic effect of the original Lycurgus cup. </div

Antiaromatic Covalent Organic Frameworks Based on Dibenzopentalenes

Despite their inherent instability, 4n pi-systems have recently received significant attention due to their unique optical and electronic properties. In dibenzopentalene, benzanellation stabilizes the highly antiaromatic pentalene core, without compromising its amphoteric redox behavior or small HOMO–LUMO energy gap. However, incorporating such molecules in organic devices as discrete small molecules or ill-defined amorphous polymers can limit the performance (e.g. due to solubility in the electrolyte solution or low internal surface area). Covalent organic frameworks, on the contrary, are highly ordered, porous, and crystalline materials that can provide a platform to align molecules with specific properties in a well-defined, ordered environment. We synthesized the first antiaromatic framework materials and obtained a series of three highly crystalline and porous covalent organic frameworks based on dibenzopentalene. Potential applications of such antiaromatic bulk materials were explored: COF films show a conductivity of 4 × 10^(−8) S cm^(−1) upon doping and exhibit photoconductivity upon irradiation with visible light. Investigations as battery electrode materials demonstrate their ambipolar nature and the ability to store both anions and Li ions with enhanced charge storage capabilities compared to an aromatic COF or the conductive carbon material. This work showcases antiaromaticity as a new design principle for functional framework materials

Multiscale Structural Control of Linked Metal-Organic Polyhedra Gel by Aging-Induced Linkage-Reorganization

Assembly of permanently porous metal-organic cages with functional polymers forms soft supramolecular networks featuring both porosity and processability. However, the amorphous nature of such soft materials complicates their characterization and thus limits structural control. Here we demonstrated that aging is an effective strategy to control the hierarchical network of supramolecular gels, which are assembled from organic ligands as linkers and metal-organic polyhedra (MOP) as junctions. Normally, the initial gel formation by rapid gelation leads to a kinetically trapped structure with low controllability. Through a controlled post-synthetic aging process, we show that it is possible to tune the network of the linked MOP gel over multiple length scales. This process allows control on the molecular-scale rearrangement of interlinking MOPs, mesoscale fusion of colloidal particles and macroscale densification of the whole colloidal network. In this work we elucidate the relationships between the gel properties, such as porosity and rheology, and their hierarchical structures, which suggest that porosity measurement can be used as a powerful tool to characterize the microscale structural transition of the amorphous gels. This aging strategy can be applied in other supramolecular polymer systems particularly containing kinetically controlled structures and shows an opportunity to engineer the structure and porosity of amorphous porous soft materials for further applications