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A protocol for the bottom-up self-assembly of nanogaps is developed through molecular linking of gold nanoparticles (AuNPs). Two π-conjugated oligo(phenylene ethynylene) molecules (OPE) with dithiocarbamate anchoring groups are used as ligands for the AuNPs. OPE-4S with a dithiocarbamate in each end of the molecule and a reference molecule OPE-2S with only a single dithiocarbamate end group. The linking mechanism of OPE-4S is investigated by using a combination of TEM, UV-Vis absorption and surface enhanced Raman spectroscopy (SERS) as well as studying the effect of varying the OPE-4S to AuNP concentration ratio. UV-Vis absorption confirms the formation of AuNP aggregates by the appearance of an extended plasmon band (EPB) for which the red shift and intensity depend on the OPE-4S:AuNP ratio. SERS confirms the presence of OPE-4S and shows a gradual increase of the signal intensity with increasing OPE-4S:AuNP ratios up to a ratio of about 4000, after which the SERS intensity does not increase significantly. For OPE-2S, no linking is observed below full coverage of the AuNPs indicating that the observed aggregate formation at high OPE-2S:AuNP ratios, above full AuNP coverage, is most likely of a physical nature (van der Waals forces or π-π interactions).

In the presented work, the electrochemical stability of platinized silicon carbide is studied. Postmortem transmission electron microscopy and X-ray photoelectron spectroscopy were used to document the change in the morphology and structure upon potential cycling of Pt/SiC catalysts. Two different potential cycle aging tests were used in order to accelerate the support corrosion, simulating start-up/shutdown and load cycling. On the basis of the results, we draw two main conclusions. First, platinized silicon carbide exhibits improved electrochemical stability over platinized active carbons. Second, silicon carbide undergoes at least mild oxidation if not even silicon leaching.

A colloidal synthesis approach is presented that allows systematic studies of the properties of supported proton exchange membrane fuel cell (PEMFC) catalysts. The applied synthesis route is based on the preparation of monodisperse nanoparticles in the absence of strong binding organic stabilizing agents. No temperature post-treatment of the catalyst is required rendering the synthesis route ideally suitable for comparative studies. We report work concerning a series of catalysts based on the same colloidal Pt nanoparticle (NP) suspension, but with different high surface area (HSA) carbon supports. It is shown that for the prepared catalysts the carbon support has no catalytic co-function, but carbon pre-treatment leads to enhanced sticking of the Pt NPs on the support. An unwanted side effect, however, is NP agglomeration during synthesis. By contrast, enhanced NP sticking without agglomeration can be accomplished by the addition of an ionomer to the NP suspension. The catalytic activity of the prepared catalysts for the oxygen reduction reaction is comparable to industrial catalysts and no influence of the particle size is found in the range of 2-5 nm.

Summary: A new system was deviced that allows the electrolytical detachment of platinum microcoils at variable lengths for the endovascular treatment of intracranial aneurysms. The detachment element consists of two short platinum coil segments, which are connected by a threat of stainless steel. The steel threat is interrupted by electrolysis, using a continuous current with 1-2 mA at a voltage of 4-8 Volt. The average detachment time in heparinized blood is about 30-40 sec. The detachment elements can be used to connect either an insertion wire with a platinum coil or to connect several segments of platinum coils with variable helices and lengths. If several detachment elements are integrated in a coil, electrolysis interrupts only the element, which is next beyond the distal tip of the catheter. The electrolytical process does not affect the detachment elements proximal and distal to the element adjacent to the tip of the catheter. Single or several coil segments can be pulled back into the microcatheter if necessary. The system is expected to allow a faster and more complete endovascular coil occlusion of intracranial aneurysms. The principles described in this paper are claimed by the German pending patent DE 100 10840 A1.

Report on the application of a new (valve equipped) detachable balloon for percutaneous transvasal embolization therapy in 372 patients with (noncerebral) curative preoperative and palliative indications.