Reiner Wahl

Three-dimensional metallization of microtubules

Abstract Microtubules (MTs), components of the cytoskeletons of eukaryotic cells, are protein filaments with outer diameters of 25 nm and lengths of several micrometers. Due to their large geometrical aspect ratios, they are well suited for use as biomolecular templates for the fabrication of magnetic and electrically conductive nanowires. Three-dimensional metallization of these MTs is demonstrated by an electroless deposition technique of nickel initiated by molecular palladium catalysts. In this study of the deposition conditions, it is shown that in the use of electroless plating for the metallization of tubulin assemblies the process parameters, such as temperature and pH, need to be adjusted to the chemical conditions of the in-vitro self-assembly process of MTs. The activated and metallized MTs have been characterized by scanning electron microscopy and transmission electron microscopy. Depending on the distribution of the Pd catalyst particles after MT activation, we found that a minimum nickel thickness of about 10 nm is required to produce a continuous film.

Superconductivity at 20 mK in compacted submicrometer platinum powders

Abstract The superconducting transition temperature and critical magnetic field observed in compacted Pt powder samples with sub micrometer grain size are as high as 20 mK and 18 mT and thus more than one order of magnitude larger than for those with larger (micrometer) grain size. The submicrometer samples exhibit strong lattice strain and significantly smaller Debye temperatures compared to bulk platinum. Moreover, the ferromagnetic spin fluctuations of the conduction electrons are partially quenched in these compacts.