We fabricated flexible, transparent, and conductive metal grids as transparent conductive materials (TCM) with adjustable properties by direct nanoimprinting of self-assembling colloidal metal nanowires. Ultrathin gold nanowires (diameter below 2 nm) with high mechanical flexibility were confined in a stamp and readily adapted to its features. During drying, the wires self-assembled into dense bundles that percolated throughout the stamp. The high aspect ratio and the bundling yielded continuous, hierarchical superstructures that connected the entire mesh even at low gold contents. A soft sintering step removed the ligand barriers but retained the imprinted structure. The material exhibited high conductivities (sheet resistances down to 29 Ω/sq) and transparencies that could be tuned by changing wire concentration and stamp geometry. We obtained TCMs that are suitable for applications such as touch screens. Mechanical bending tests showed a much higher bending resistance than commercial ITO: conductivity dropped by only 5.6% after 450 bending cycles at a bending radius of 5 mm.

A straightforward route to hybrid nanostructures of metal cores with conductive polymers and their application as sintering-free inks is described.

Ultrathin gold nanowires (AuNWs) with diameters below 2 nm and high aspect ratios are considered to be a promising base material for transparent electrodes. To achieve the conductivity expected for this system, oleylamine must be removed. Herein we present the first study on the conductivity, optical transmission, stability, and structure of AuNW networks before and after sintering with different techniques. Freshly prepared layers consisting of densely packed AuNW bundles were insulating and unstable, decomposing into gold spheres after a few days. Plasma treatments increased the conductivity and stability, coarsened the structure, and left the optical transmission virtually unchanged. Optimal conditions reduced sheet resistances to 50 Ω/sq.

Ultrathin gold nanowires are unusual colloidal objects that assemble into bundles with line contacts between parallel wires. Each molecule in the contact line interacts with many ligand and solvent molecules. We used X-ray scattering and electron microscopy to study how these interactions control assembly.

Hierarchical structures lend strength to natural fibers made of soft nanoscale building blocks. Intermolecular interactions connect the components at different levels of hierarchy, distribute stresses, and guarantee structural integrity under load. Here, we show that synthetic ultrathin gold nanowires with interacting ligand shells can be spun into biomimetic, free-standing microfibers. A solution spinning process first aligns the wires, then lets their ligand shells interact, and finally converts them into a hierarchical superstructure. The resulting fiber contained 80 vol % organic ligand but was strong enough to be removed from the solution, dried, and mechanically tested. Fiber strength depended on the wire monomer alignment. Shear in the extrusion nozzle was systematically changed to obtain process-structure-property relations. The degree of nanowire alignment changed breaking stresses by a factor of 1.25 and the elongation at break by a factor of 2.75. Plasma annealing of the fiber to form a solid metal shell decreased the breaking stress by 65%.