Alexander Küller

Structured and Gradient Polymer Brushes from Biphenylthiol Self-Assembled Monolayers by Self-Initiated Photografting and Photopolymerization (SIPGP)

The self-initiated photografting and photopolymerization (SIPGP) of styrene, methyl methacrylate, and tert-butyl methacrylate on structured self-assembled monolayers (SAMs) of electron beam cross-linked omega-functionalized biphenylthiols SAMs on gold was investigated. Polymer brushes with defined thickness can be prepared on crosslinked benzyl-, phenyl-, hydroxyl-, and amino-functionalized SAMs, whereas non-cross-linked SAM regions desorb from the surface during the SIPGP process. By the preparation of brush gradients on different functionalized SAMs, it was demonstrated that the resulting polymer brush layer thickness is determined by the locally applied electron beam dosage. Defined micro-nanostructured polymer brush patterns can be prepared down to a size of 50 nm. Finally, it was shown that polymer brushes obtained by the SIPGP process have a branched architecture.

The proteome of rat olfactory sensory cilia.

Olfactory sensory neurons expose to the inhaled air chemosensory cilia which bind odorants and operate as transduction organelles. Odorant receptors in the ciliary membrane activate a transduction cascade which uses cAMP and Ca2+ for sensory signaling in the ciliary lumen. Although the canonical transduction pathway is well established, molecular components for more complex aspects of sensory transduction, like adaptation, regulation, and termination of the receptor response have not been systematically identified. Moreover, open questions in olfactory physiology include how the cilia exchange solutes with the surrounding mucus, assemble their highly polarized set of proteins, and cope with noxious substances in the ambient air. A specific ciliary proteome would promote research efforts in all of these fields. We have improved a method to detach cilia from rat olfactory sensory neurons and have isolated a preparation specifically enriched in ciliary membrane proteins. Using LC‐ESI‐MS/MS analysis, we identified 377 proteins which constitute the olfactory cilia proteome. These proteins represent a comprehensive data set for olfactory research since more than 80% can be attributed to the characteristic functions of olfactory sensory neurons and their cilia: signal processing, protein targeting, neurogenesis, solute transport, and cytoprotection. Organellar proteomics thus yielded decisive information about the diverse physiological functions of a sensory organelle.

pH-amplified exponential growth multilayers: a facile method to develop hierarchical micro- and nanostructured surfaces.

We report a direct method to amplify the exponential growth of multilayers significantly by the alternating deposition of polyethylenimine (PEI) at high pH and poly(acrylic acid) (PAA) at low pH. The alternating pH switches the degree of ionization of the polyelectrolytes in the multilayers, which enhances the diffusion of PEI into and out of the film and hence increases the deposited mass per cycle. The synergetic action of the pH-tunable charge density and diffusivity of the weak polyelectrolytes provides a new method for the enhanced growth of multilayers with hierarchal micro- and nanostructured surfaces.

Nanostructuring of silicon by electron-beam lithography of self-assembled hydroxybiphenyl monolayers

We report the fabrication of silicon nanostructures using aromatic hydroxybiphenyl self-assembled monolayers as ultrathin (1.1 nm) negative tone electron-beam resist. The formation of the monolayer and the electron-induced crosslinking have been characterized by x-ray photoelectron spectroscopy. Nanometer size patterns were defined by electron-beam lithography in the molecular layer and transferred into silicon by wet chemical etching with potassium hydroxide. We demonstrate the fabrication of silicon line gratings with a resolution of ∼20 nm and of isolated silicon lines with linewidths down to ∼10 nm.

Electron-beam lithography with aromatic self-assembled monolayers on silicon surfaces

Aromatic self-assembled monolayers are formed via the coupling of hydroxy head groups to hydrogen-terminated silicon surfaces. We first investigate the application of 4-hydroxy-1,1′-biphenyl as an ultrathin negative tone electron-beam (e-beam) resist using conventional e-beam lithography with a beam energy of 3 keV. We demonstrate the fabrication of nanometer silicon patterns that are transferred using the modified monolayer as a resist mask for a wet chemical etching process in potassium hydroxide. The necessary dose for complete cross linking was determined to be 20 mC/cm2. Using this approach, isolated silicon structures with lateral dimensions down to ∼10 nm and periodic structures with a resolution of ∼20 nm were fabricated. On the other hand, 4′-nitro-4-hydroxy-1,1′-biphenyl has been found not to form monolayers suitable for chemical lithography on hydrogenated silicon surfaces. Upon adsorption, the nitro groups are partially reduced to amino groups by the hydrogenated surface and some of the molecu...