Structured polymer fibers with diameters down to tens of nanometers are of interest for applications in filters, in composite reinforcement, or as templates for the preparation of functional nanotubes. The Figure shows fibers of poly‐L‐lactide produced by electrospinning from a dichloromethane solution exhibiting regular pores or pits in the 100 nm range.

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pected, when the nanocrystal is isolated on a substrate a Coulomb blockade behavior is observed. With a monolayer both ohmic and Coulomb blockade contributions are observed, whereas with a fcc structure a well-defined ohmic behavior is seen. ExperimentalSilver nanosized particles were synthesized using reverse micelles, as described previously [19,20]: Colloidal silver particles were prepared by mixing two reverse-micellar solutions having the same water-content (i.e., the molarThe first was made with 30 % Ag(AOT) and 70 % Na(AOT), and the second with hydrazine N 2 H 4 as reducing agent with an overall concentration of 71 0 ±2 M and with 100 % Na(AOT). This gave an average particle diameter of 3.4 nm with 43 % size distribution. Dodecanethiol was added to the micellar solution (1 mL/cm 3 ). Selective reaction with the silver atoms at the interface of the particles occurred and the coated particles were then extracted from reverse micelles. The powder of coated nanocrystals thus obtained was then dispersed in hexane, giving an optically clear solution. The size distribution was still rather large (30 %), and to reduce it a size-selected precipitation process [20] was used. In this process two solvents, such as hexane and pyridine, are mixed. The first is a good solvent and the second a poor solvent for the alkyl chains. With this solvent mixture, the larger coated particles flocculated whereas the smaller ones remain in the solution, thus providing size selection. By repeating this process several times, a homogenous clear colloidal solution of dispersed 4.3 nm nanocrystals is obtained. The concentration of nanocrystals with final size distribution around 13 % was controlled.

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