NanoAnalytics GmbH

Bad Münster am Stein-Ebernburg, Germany

NanoAnalytics GmbH

Bad Münster am Stein-Ebernburg, Germany
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Seela F.,Center for Nanotechnology | Seela F.,University of Osnabrück | Pujari S.S.,Center for Nanotechnology | Pujari S.S.,University of Osnabrück | Schafer A.H.,NanoAnalytics GmbH
Tetrahedron | Year: 2011

Nucleoside hydrogels based on benzyl azide 'click' conjugates of 8-aza-7-deaza-2′-deoxyadenosine bearing 7-ethynyl, 7-octa-(1,7-diynyl), and 7-tri-prop-2-ynyl-amine side chains were synthesized (1, 3, 4). The cycloaddition adduct with the shortest linker (1) yields the most powerful hydrogelator forming stable gels at a concentration of 0.3 wt % of 1 in water. One molecule of 1 catches 7500 water molecules. Cycloaddition of the 8-aza-7-deaza-7-azido-2′-deoxyadenosine (9) and 3-phenyl-1-propyne (10) leads to the isomeric conjugate 2, with a C-N connectivity between the nucleobase and triazole moiety. This gel is less stable than that of the adduct 1. Both gels show a similar stability over a wide pH range (4.0-10.0). Xerogels of 1 and 2 studied by scanning electron microscopy (SEM) reveal that both click adducts (1 and 2) form long fibers spontaneously. © 2011 Elsevier Ltd. All rights reserved.

Ranganath K.V.S.,University of Munster | Kloesges J.,University of Munster | Schafer A.H.,Nano Analytics GmbH | Glorius F.,University of Munster
Angewandte Chemie - International Edition | Year: 2010

Superficial success: A chiral N-heterocyclic carbene (NHC *) is used to modify Fe3O4/Pd nanoparticles, which then catalyze asymmetric α-arylations. This successful synthesis of a heterogeneous catalyst and its appliation in asymmetric catalysis is in stark contrast to the simple immobilization of an established chiral homogeneous catalyst. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kehr N.S.,University of Munster | Schafer A.,NanoAnalytics GmbH | Ravoo B.J.,University of Munster | De Cola L.,University of Munster
Nanoscale | Year: 2010

Microcontact printing (mCP) is used to immobilize dyes and peptides asymmetrically, by a "peptide coupling" reaction, on monolayers of zeolite L crystals in the contact area between the stamp and the surface of the monolayer. Chemically patterned surfaces of monolayers of zeolite L crystals are obtained by using patterned stamps with different ink solutions. Additional printing of functionalized nano-objects on SAMs of zeolite L crystals is demonstrated. © 2010 The Royal Society of Chemistry.

Mardyukov A.,University of Munster | Li Y.,University of Munster | Dickschat A.,University of Munster | Schafer A.H.,Nanoanalytics GmbH | Studer A.,University of Munster
Langmuir | Year: 2013

The preparation of polymer brushes (PBs) bearing α- hydroxyalkylphenylketone (2-hydroxy-2-methyl-1-phenylpropan-1-one) moieties as photoreactive polymer backbone substituents is presented. Photoreactive polymer brushes with defined thicknesses (up to 60 nm) and high grafting densities are readily prepared by surface initiated nitroxide mediated radical polymerization (SINMP). The photoactive moieties can be transformed via Norrish-type I photoreaction to surface-bound acyl radicals. Photolysis in the presence of a persistent nitroxide leads to chemically modified PBs bearing acylalkoxyamine moieties as side chains resulting from trapping of the photogenerated acyl radicals with nitroxides. Application of functionalized nitroxides to the photochemical PB postmodification provides functionalized PBs bearing cyano, polyethylene glycol (PEG), perfluoroalkyl, and biotin moieties. As shown for one case, photochemical postfunctionalization of the PB through a mask using a biotin-conjugated nitroxide as the trapping reagent leads to the corresponding site-selective chemically modified PB, which is successfully used for site-specific streptavidin immobilization. Surface analysis of PBs was performed by contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), attenuated total reflection (ATR), fourier transform infrared (FTIR) spectroscopy, and fluorescence microscopy. © 2013 American Chemical Society.

Kehr N.S.,University of Munster | Riehemann K.,University of Munster | El-Gindi J.,University of Munster | Schafer A.,NanoAnalytics GmbH | And 3 more authors.
Advanced Functional Materials | Year: 2010

Chemically functionalized self-assembled monolayers made by disk-shaped zeolite L nanocrystals are used as models for biocompatible surfaces to study cell-adhesion behavior. Different chemical groups lead to different cellular behavior and fluorescent-molecule-loaded zeolites allow the position of the cells to be determined. Furthermore, a patterned monolayer of asymmetrically functionalized zeolite L obtained by microcontact chemistry is used to grow cells. A spatial recognition of the cells, which proliferate only on the bioactivemolecule-functionalized stripes, is possible. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dickschat A.T.,University of Munster | Behrends F.,University of Munster | Buhner M.,NanoAnalytics GmbH | Ren J.,University of Munster | And 3 more authors.
Chemistry - A European Journal | Year: 2012

The synthesis of bifunctional mesoporous silica nanoparticles is described. Two chemically orthogonal functionalities are incorporated into mesoporous silica by co-condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes. Post-functionalization is achieved by orthogonal surface chemistry. A thiol-ene reaction, Cu-catalyzed 1,3-dipolar alkyne/azide cycloaddition, and a radical nitroxide exchange reaction are used as orthogonal processes to install two functionalities at the surface that differ in reactivity. Preparation of mesoporous silica nanoparticles bearing acidic and basic sites by this approach is discussed. Particles are analyzed by solid state NMR spectroscopy, elemental analysis, infrared-spectroscopy, and scanning electron microscopy. As a first application, these particles are successfully used as cooperative catalysts in the Henry reaction. Cooperative clicking: Bifunctional mesoporous silica particles were synthesized by orthogonal surface chemistry. A thiol-ene reaction, a copper-catalyzed 1,3-dipolar cycloaddition and a radical nitroxide exchange reaction were used as orthogonal processes for the introduction of the acid and base functionalities (see scheme). Catalytic activities of these bifunctionalized inorganic/organic hybrid materials were studied on the Henry reaction. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vasquez-Cespedes S.,University of Munster | Chepiga K.M.,University of Munster | Moller N.,University of Munster | Schafer A.H.,Nano Analytics GmbH | Glorius F.,University of Munster
ACS Catalysis | Year: 2016

A reusable copper-based catalyst system was employed for the direct arylation of electron-rich heteroarenes. Under mild and operationally simple reaction conditions good yields and selectivities were obtained using diaryliodonium salts as coupling partners. A combination of experimental methods including kinetic studies, filtration tests, and a series of analytical tools (TXRF, ICP-MS, SEM, XPS, TEM, EFTEM) provide evidence for catalytically active soluble nanoparticles formed from an amorphous heterogeneous precursor. Mechanistic studies hint at a redox-neutral process which promotes counterion dissociation from the diaryliodonium salt by a copper(II) oxide species. © 2016 American Chemical Society.

Wagner H.,University of Munster | Brinks M.K.,University of Munster | Hirtz M.,University of Munster | Schafer A.,Nanoanalytics GmbH | And 2 more authors.
Chemistry - A European Journal | Year: 2011

This article describes the application of nitroxide exchange reactions of surface-bound alkoxyamines as a tool for reversible chemical modification of self-assembled monolayers (SAMs). This approach is based on radical chemistry, which allows for introduction of various functional groups and can be used to reversibly introduce functionalities at surfaces. To investigate the scope of this surface chemistry, alkoxyamines with different functionalities were synthesized and were then applied to the immobilization of, for example, dyes, sugars, or biotin. Surface analysis was carried out by contact angle, X-ray photoelectron spectroscopy, and fluorescence microscopy measurements. The results show that this reaction is highly efficient, reversible, and mild and allows for immobilization of various sensitive functional groups. In addition, Langmuir-Blodgett lithography was used to generate structured SAMs. Site-selective immobilization of a fluorescent dye could be achieved by nitroxide exchange reactions. A radical exchange: Chemical modification of silicon surfaces with alkoxyamine-based self-assembled monolayers (SAMs) was achieved by reversible radical nitroxide exchange reactions. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The present invention relates to an arrangement (1) for impedance measurements across the surface of a tubular membrane manufactured from a semi-permeable material, the arrangement (1) comprising:a) a tubular outer electrode (2) having a longitudinal axis;b) at least one tubular membrane (3) manufactured from a semi-permeable membrane and having a longitudinal axis, the at least one tubular membrane (3) being located within the tubular outer electrode (2) in such a way that the longitudinal axis of the tubular membrane (3) is substantially parallel to the longitudinal axis of the tubular outer electrode (2);c) at least one inner electrode (4) in the form of a wire, tube or rod having a longitudinal axis, the at least one inner electrode (4) being located within the at least one tubular membrane (3) in such a way that the longitudinal axis of the at least one inner electrode (4) is substantially parallel to the longitudinal axis of the at least one tubular membrane (3). The invention also relates to a process for measuring the impedance across the surface of a tubular membrane manufactured from a semi-permeable material.

PubMed | NanoAnalytics GmbH and University of Munster
Type: Journal Article | Journal: ACS applied materials & interfaces | Year: 2016

Nanoparticle density gradients on surfaces have attracted interest as two-dimensional material surfaces that can mimic the complex nano-/microstructure of the native extracellular matrix, including its chemical and physical gradients, and can therefore be used to systematically study cell-material interactions. In this respect, we report the preparation of density gradients made of bifunctional zeolite L crystals on glass surfaces and the effects of the density gradient and biopolymer functionalization of zeolite L crystals on cell adhesion. We also describe how we created Janus density gradient surfaces by gradually depositing two different types of zeolite L crystals that were functionalized and loaded with different chemical groups and guest molecules onto the two distinct sides of the same glass substrate. Our results show that more cells adhered on the density gradient of biopolymer-coated zeolites than on uncoated ones. The number of adhered cells increased up to a certain surface coverage of the glass by the zeolite L crystals, but then it decreased beyond the zeolite density at which a higher surface coverage decreased fibroblast cell adhesion and spreading. Additionally, cell experiments showed that cells gradually internalized the guest-molecule-loaded zeolite L crystals from the underlying density gradient containing bifunctional zeolite L crystals.

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