Publications by authors named "Michael Philippi"

High-temperature treatment of functional nanomaterials, through postsynthesis calcination, often represents an important step to unlock their full potential. However, such calcination steps usually severely limit the preparation of colloidal solutions of the nanoparticles due to the formation of sintered agglomerates. Herein, a simple route is reported to obtain colloidal solutions of calcined n-conductive antimony doped tin oxide (ATO) as well as titanium dioxide (TiO ) nanoparticles without the need for additional sacrificial materials.

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Qualitative and quantitative analysis of transient signaling platforms in the plasma membrane has remained a key experimental challenge. Here, biofunctional nanodot arrays (bNDAs) are developed to spatially control dimerization and clustering of cell surface receptors at the nanoscale. High-contrast bNDAs with spot diameters of ≈300 nm are obtained by capillary nanostamping of bovine serum albumin bioconjugates, which are subsequently biofunctionalized by reaction with tandem anti-green fluorescence protein (GFP) clamp fusions.

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Sphingomyelin is a dominant sphingolipid in mammalian cells. Its production in the Golgi traps cholesterol synthesized in the ER to promote formation of a sphingomyelin/sterol gradient along the secretory pathway. This gradient marks a fundamental transition in physical membrane properties that help specify organelle identify and function.

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We report an optimized two-step thermopolymerization process carried out in contact with micropatterned molds that yields porous phenolic resin dual-use stamps with topographically micropatterned contact surfaces. With these stamps, two different parallel additive substrate manufacturing methods can be executed: capillary stamping and decal transfer microlithography. Under moderate contact pressures, the porous phenolic resin stamps are used for nondestructive ink transfer to substrates by capillary stamping.

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We report the parallel generation of close-packed ordered silane nanodot arrays with nanodot diameters of few 100 nm and nearest-neighbor distances in the one-micron range. Capillary nanostamping of heterocyclic silanes coupled with ring-opening triggered by hydroxyl groups at the substrate surfaces yields nanodots consisting of silane monolayers with exposed terminal functional groups. Using spongy mesoporous silica stamps with methyl-terminated mesopore walls inert towards the heterocyclic silanes, we could manually perform multiple successive stamping cycles under ambient conditions without interruptions for ink refilling.

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Dense layers of overlapping three-dimensional (3D) gold nanodendrites characterized by high specific surfaces as well as by abundance of sharp edges and vertices creating high densities of SERS hotspots are promising substrates for SERS-based sensing and catalysis. We have evaluated to what extent structural features of 3D gold nanodendrite layers can be optimized by the initiation of 3D gold nanodendrite growth at gold particles rationally positioned on silicon wafers. For this purpose, galvanic displacement reactions yielding 3D gold nanodendrites were guided by hexagonal arrays of parent gold particles with a lattice constant of 1.

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Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) monoliths containing regular arrays of macropores (diameter ≈1.1 µm, depth ≈0.7 µm) at their surfaces are used to pattern substrates by patterning modes going beyond the functionality of classical solid elastomer stamps.

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