Redox-promoted self-assembly of an eight-residue cyclic D,L-α-peptide bearing four 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) side chains results in the formation of electronically delocalized peptide nanotubes hundreds of nm in length. The supramolecular approach described provides a rational basis for the design and fabrication of 1-D materials with potential utility in optical and electronic devices.
A two-turn, eight-armed, rectangular Si/Ni heterogeneous nanospring structure on Si(100) has been fabricated using a multilayer glancing-angle deposition technique. The multilayered nanosprings with a height of approximate to 1.98 mu m were composed of alternating layers of amorphous Si nanorods approximate to 580 nm in length and face-centered cubic Ni nanorods approximate to 420 nm in length, both with a diameter of approximate to 35 nm. The magnetic anisotropy of the nanosprings showed that the in-plane easy and hard axes were parallel and perpendicular to the Ni nanorod plane, respectively. The out-of-plane magnetic hysteresis loop was very sensitive to the applied magnetic field direction when rotating the nanosprings about their in-plane hard axis, and the magnetization measurement revealed that the nanosprings tilted at approximate to 7.5 degrees toward the plane of the Si nanorods. The magnetic anisotropy of the nanosprings is determined by their structure, and the experimental results can be interpreted by the shape anisotropy energy.
Silica-cone patterns self-assembled from well-aligned nanowires are synthesized using gallium droplets as the catalyst and silicon wafers as the silicon source. The cones form a triangular pattern array radially on almost the whole surface of the molten Ga ball. Detailed field-emission scanning electron microscopy (SEM) analysis shows that the cone-pattern pieces frequently slide off and are detached from the molten Ga ball surface, which leads to the exposure of the catalyst surface and the growth of a new batch of silicon oxide nanowires as well as the cone patterns. The processes of growth and detachment alternate, giving rise to the formation of a volcano-like or a flower-like structure with bulk-quantity pieces of cone patterns piled up around the Ga ball. Consequently, the cone-patterned layer grows batch by batch until the reaction is terminated. Different to the conventional metal-catalyzed growth model, the batch-by-batch growth of the triangular cone patterns proceeds on the molten Ga balls via alternate growth on and detachment from the catalyst surface of the patterns; the Ga droplet can be used continuously and circularly as an effective catalyst for the growth of amorphous SiOx nanowires during the whole growth period. The intriguing batchwise growth phenomena may enrich our understanding of the vapour-liquid-solid (VLS) growth mechanism for the catalyst growth of nanowires or other nanostructures and may offer a different way of self-assembling novel silica nanostructures.