Secondary ligand-induced orthogonal self-assembly of silver nanoclusters into superstructures with enhanced NIR emission.

Orthogonal self-assembly is one of the crucial strategies for forming complex and hierarchical structures in biological systems. However, creating such ordered complex structures using synthetic nanoparticles is a challenging task and requires a high degree of control over structure and multiple non-covalent interactions. In this context, nanoarchitectonics serves as an emerging tool to fabricate complex functional materials. Here, we present a secondary ligand-induced orthogonal self-assembly of atomically precise silver nanoclusters into complex superstructures. Specifically, we use Ag14NCs protected with naphthalene thiol and 1,6-bis(diphenylphosphino)hexane ligands. Controlled addition of 1,6-bis(diphenylphosphino)hexane, the secondary ligand resulted in a self-assembled supracolloidal structure including helical fibers, spheres, and nanosheets. The self-assembly process is tunable by controlling the molar ratio of the ligand. The resulting superstructures exhibit enhanced NIR emission due to restricted intramolecular motion. This demonstrates that by tuning supramolecular interactions, hierarchical nanostructures with desired properties similar to biomolecules can be obtained from atomically precise building blocks.

Role of Zinc Oxide in the Compounding Formulation on the Growth of Nonstoichiometric Copper Sulfide Nanostructures at the Brass-Rubber Interface.

Tire technology has evolved substantially by the introduction of brass-coated steel cords (BCSCs) in radial tires. The durability of radial tires is dependent on the integrity of the brass-rubber interface composed predominantly of nonstoichiometric copper sulfide (Cu2-x S, where x = 1 to 2) nanostructures whose morphology and characteristics are dependent upon the crucial rubber additive, ZnO. Its higher concentration impacts environmental sustainability, while at lower levels, there is insufficient bonding between steel and the rubber thus affecting tire's safety. This brings in the need for an optimum ZnO concentration to be used in radial tires and is thus the theme of the present work. The changes in the properties of interfacial nanostructures such as morphology, thickness, crystallinity, and chemical composition were studied at various ZnO concentrations. We adopted our previously reported methodology, the "brass mesh experiment", to investigate the thickness of nanostructures at varied ZnO concentrations using transmission electron microscopy (TEM). Significant results were obtained from field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman imaging and X-ray photoelectron spectroscopy (XPS). In conjunction with a more practical experimental technique, namely the measurement of pull-out force (POF), it has been concluded that 9 parts per hundred rubber (PHR) ZnO is essential for the optimum growth of nanostructures and is considered to be the optimum for the composition studied. We believe that the scientific approach outlined in the manuscript would help the tire- and the material science communities to widen the knowledge of understanding sustainability in tire industries. It is estimated that the optimization presented here can save $400-450 million for the tire industry and 2.4 million tons of ZnO per year.