Nanotube-like structures

Abstract Polyferrocenyldimethyl-silane (PFS) diblock copolymers with polyisoprene (PFS-PI) or with polydimethylsiloxane (PFS-PDMS) self-assemble in simple alkane solvents to form what appear by TEM to be dense flexible cylinders (nanowires) or nanotube-like structures. Typical widths are on the order of 20 to 30 nm, with variable lengths often greater than 10 un. The structures that form, and the dimensions of the tube-like structures or wires, depend upon the composition of the polymers and the lengths of the blocks. Light scattering experiments show that the PFS-PDMS (block ratio 1 12) solutions aged... 

We also noticed that the formation of these structures is sensitive to the temperature history of the sample. For example, the sample shown in Fig. 4a, cooled from 61 °C to room temperature (ca. 23 °C) over 2h and then aged, exhibited long nanotube-like structures [8,15], In contrast, a sample of the same solution of PFS40-PDMS480 in w-decane heated at 61 °C for 30 min and then rapidly quenched on the TEM grid, exhibited a mixture of star-like and short rod micelles (Fig. 5). 

This high sensitivity to the temperature history encouraged us to study the influence of temperature on the morphology of self-assembled structure. We used the solution slowly cooled from 61 °C to 25 °C (see Fig. 4a) showing nanotube-like structures as our starting point,... 

Fig. 6 TEM micrograph of PFS40-6-PDMS480 assemblies formed in w-decane at 50 °C. The inset shows nanotube-like structures at 25 °C...

The preparation of Titania nanocoils has been yet not investigated in literature. However, quite recent results258 show that the effective structure of Titania nanotube likely produced by controlled anodization process is that of a helical (compressed) nanocoil. Fig. 11 shows this concept. It was also demonstrated that the formation of these helical nanocoils improves the photo-generated current compared to samples after short anodization where only a Titania layer is formed. 

Inorganic Nanoclusters with Fullerene-Like Structure and Nanotubes... 

II. CLASSIFICATION OF DIFFERENT INORGANIC COMPOUNDS FORMING FULLERENE-LIKE STRUCTURES AND NANOTUBES... 

The Ba.C) N, nanotubes and fullerene-like structures have been synthesized by various laboratories in recent years. The most popular method is the plasma arc technique. The first report on the synthesis of BN nanotubes was by Zettl and coworkers (55). Since BN is an insulator, a composite anode was prepared from a tungsten rod with an empty bore in the center, which was stuffed with a pressed hexagonal BN powder. For the cathode, a water-cooled Cu rod was used. The collected gray soot contained limited amount of multi wall BN nanotubes. It is possible that in this case, the tungsten serves also as a catalyst. By perfecting this method, macroscopic amounts of double-wall BN nanotubes of a uniform diameter (2 nm)... 

Single spatial molecules fullerens, single-walled nanotubes, fullerene-like structures... 

Fig. 1.18 Schematic illustration of (a) a globular protein, adsorbed on (b) a nanotube and (c) an AFM image, showing protein (bright dot-like structures decorating the line-...

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