Achim Weber

Isothermal titration calorimetry of molecularly imprinted polymer nanospheres

Ultrasensitive isothermal titration calorimetry was used to generate thermodynamic data to assess the binding properties of molecularly imprinted polymer microgels. Microgels were imprinted using L-boc-phenylalanine anilide (L-BFA) and then utilized in binding experiments with a variety of probe molecules, structurally closely related to the template molecule. Significant differences were observed between the binding enthalpy of the original template L-BFA and those of D-BFA, L-boc-phenylalanine, L-boc-tryptophane, and L-boc-tyrosine.

Supported organometallic complexes. Part XX. Hydroformylation of olefins with rhodium(I) hybrid catalysts

Abstract The rhodium(I) complexes HRh(CO)[Ph2P(CH2)xSi(OMe)3]3 [1a,b(T0)3; a: x=3, b: x=6; T: T-type silicon atom, three oxygen neighbors] were sol–gel processed with the bifunctional cocondensation agent (MeO)3Si(CH2)6Si(OMe)3 (T–C6–T) and in a separate reaction also with three additional equivalents of the phosphine ligand Ph2P(CH2)xSi(OMe)3 [2a,b(T0)]. The resulting stationary phases 1a(Tn)3(Tn–C6–Tn)y, 1a(Tn)3[2a(Tn)]3(Tn–C6–Tn)y, and 1b(Tn)3[2b(Tn)]3(Tn–C6–Tn)y (n=0–3, number of Si–O–Si bonds; y: content of cocondensation agent) show a relatively narrow particle size distribution. The structural integrity of the rhodium complex 1 after the polycondensation was established by an EXAFS structure elucidation of the polysiloxane 1a(Tn)3. The obtained stationary phases proved to be efficient catalysts for the hydroformylation of 1-hexene in the presence of a wide variety of solvents in the interphase. Application of the materials containing non-coordinated ligands raised the selectivity toward hydroformylation up to 92% and the n/iso ratio to 14:1 with an average turnover number of 164 molsub molcat−1 h−1. Higher olefins than 1-hexene were also hydroformylated with catalyst D and similar turnover frequencies and selectivities were obtained. 31P CP/MAS NMR relaxation time studies (TPH, T1ρH) were carried out in the presence (interphase) or absence (stationary phase) of a swelling solvent to investigate the dynamic behavior of the catalytically active polymer 1a(Tn)3[2a(Tn)]3(Tn–C6–Tn)y. The highest mobility of the nonpolar reactive centers was achieved in nonpolar solvents like toluene, while more polar solvents like ethanol afforded the highest mobility of the overall polymer. (1H,31P) 2D WISE NMR experiments performed on the same material revealed a substantial decrease of the line width for the swollen polymer. 29Si CP/MAS NMR experiments revealed a high degree of cross-linking and a larger content of cocondensation agent than introduced before condensation.

Investigation of the Crystallisation Behaviour of Lead Titanate (PT), Lead Zirconate (PZ) and Lead Zirconate Titanate (PZT) by EXAFS-Spectroscopy and X-Ray Diffraction

Two solid solutions of lead zirconium titanates PbZrxTi1 − xO3 (x = 0.1 and 0.35) as well as the reference compounds lead titanate and lead zirconate were prepared from zirconium and titanium n-propoxide, dissolved in 2-methoxyethanol, by sol-gel process. The amorphous products after pyrolysis of the dried gels and the crystalline phases were studied by EXAFS spectroscopy to monitor the structural changes from the amorphous oxide mixture to the crystalline ceramics after calcination. Additionally, the crystalline phases were identified by X-ray diffraction (XRD).It follows from the analysis of the EXAFS data that the local order of the amorphous phases seems to be completely different from that of the crystalline phase. There is no indication of a preformation of the local order of the perovskite structure. The analysis of our EXAFS spectra can be interpreted very consistently with the assumption that in the amorphous samples a segregation exists on molecular level and the low crystallisation temperatures are a consequence of very short diffusion paths.

Synthesis, characterisation and catalytic application of sol–gel processed cationic palladium(II) complexes

The dicationic T-silyl functionalised bis(acetonitrile)(dppp)palladium(II) complex 2(T0) (see Schemexa01) was sol–gel processed with different amounts (y) of the co-condensation agent MeSi(OMe)2(CH2)6(MeO)2SiMe (D0-C6-D0) to give the new stationary phases 2a–h(Tn)(Di-C6-Di)y (y = 0, 5, 10, 15, 20, 40, 80, and 100; n = 0–3, i = 0–2). The polysiloxane matrices and the integrity of the palladium(II) complex centres were investigated by means of solid state NMR (29Si, 13C, 31P) and EXAFS spectroscopy. Dynamic NMR investigations show an increasing mobility of the hybrid polymers on going from y = 0 to 10. For higher amounts of the co-condensation agent MeSiOi/2(OX)2 − ni(CH2)6Oi/2(XO)2 − niSiMe (Di-C6-Di) the mobility tends toward that of a matrix consisting of Di-C6-Di (T/D = 0) only. NMR experiments in suspension give further evidence for considerable mobility of the interphases (formed by the penetration of stationary and mobile phases on a molecular scale). Model reactions of 2a(Tn) with different isocyanides in the interphase point to almost complete accessibility of the palladium(II) centres, even if the reactants carry sterically demanding substituents (e.g.t-Bu). The activity of the hybrid catalysts 2a–h(Tn)(Di-C6-Di)y in the ethene/CO copolymerisation is markedly dependent on the temperature and the amount y of the co-condensation agent. A maximum of activity [1600xa0g(ECO)xa0g(Pd)−1xa0h−1] is achieved with y = 10 which is 75% of the activity of the analogous homogeneous catalyst.

Structural Investigations of Tetra- and Octasubstituted (Phthalocyanine)ruthenium Complexes by EXAFS Spectroscopy

To obtain more structural information of (phthalocyaninato)ruthenium compounds, an EXAFS investigation was carried out on amorphous tBu4PcRu (1), tBu4PcRu(3-Clpy)2 (2), PcRu(3-Fpy)2 (3) and (C5H11O)8PcRu(3-Clpy)2 (4). Structural models for the four compounds are deduced from the atomic distances determined around the metal centre. A dimeric structure was found for 1, while bisaxial arrangement of the ligands was shown for 2, 3 and 4, and the structural parameters were also determined.

Structural Investigations of Oligomeric Axially Bridged Ruthenium Phthalocyanines by EXAFS Spectroscopy

To obtain more information about the structure of phthalocyaninatoruthenium compounds an EXAFS investigation was carried out on amorphous bisaxially bridged phthalocyaninatoruthenium(II) oligomers, [PcRu(tz)]nxa0(1), [PcRu(pyz)]nxa0(2) and [PcRu(dib)]nxa0(3). Detailed structural models for the three compounds were deduced from the determined atomic distances around the metal center. A bisaxial structure of the ligands could be proven for all compounds and additionally, the structure parameters could be determined.

Ink Formulation for Inkjet Printing of Streptavidin and Streptavidin Functionalized Nanoparticles

Aqueous inks containing the protein streptavidin (SAv) or nanoparticles carrying surface-attached SAv were formulated for piezoelectric inkjet printing, using glycerol and 2-propanol to adjust their dynamic viscosity and their surface tension by variation of concentration and relative ratio of the two organic components. SAv-containing inks were transferred to epoxy-functionalized glass slides by inkjet printing or spotting and the SAv compatibility of the inks and the printing process was evaluated with regard to the ligand binding capability of the transferred SAv at the glass slide surfaces: Binding of fluorescein-4-biotin and fluorescence microscopy revealed surface-patterns of SAv and SAv-covered nanoparticles and demonstrated that glycerol and 2-propanol are suitable for the formulation of complex biofunctional inks.

Water treatment by molecularly imprinted polymer nanoparticles

Molecular recognition capabilities are evoked at artificial materials by the NANOCYTES ® -technology of the Fraunhofer IGB, Stuttgart, Germany. The biomimetic nanoparticles described here possess such molecularly recognizing properties. For this purpose they carry molecularly defined binding sites at their surface. In this particular case molecularly imprinted nanospheres (nanoMIPs) were developed for the specific adsorption of micropollutants from hospital waste water. Active pharmaceutical substances and their metabolites which were not decomposed by waste water plants were chosen as model compounds. One of this model compounds is Pentoxifylline. The nanoMIPs are prepared by a miniemulsion polymerization technique, where the monomer, the template, the cross-linker, and the initiator do react in the droplet cavities of the miniemulsion. The reaction to obtain nanoMIP particles is complex, but nevertheless it runs in a single reaction chamber and in a single step chemical process. For synthesis of the polymer system p(methacrylicacid- co -ethylenglycoldimethacrylate), p(meth-acrylicacid- co -methylmethacrylate- co -ethylenglycoldimethacrylate) and p(4-vinylpyridin- co -ethylenglycoldimethacrylate) are used. The technique of miniemulsion polymerization results in particles with a typical size distribution of 50 nm to 500 nm. Additionally, an introduced magnetic core will allow the final separation of the nanoMIPs and more important of the recognized pollutants from (waste) water. We demonstrate that magnetite can be incorporated into the polymer system, and that the template Pentoxifylline does not affect the polymerization process.

Active Ester Containing Surfmer for One-Stage Polymer Nanoparticle Surface Functionalization in Mini-Emulsion Polymerization

Functional surface active monomers (surfmers) are molecules that combine the functionalities of surface activity, polymerizability, and reactive groups. This study presents an improved pathway for the synthesis of the active ester containing surfmer p-(11-acrylamido)undecanoyloxyphenyl dimethylsulfonium methyl sulfate (AUPDS). Further, the preparation of poly(methyl methacrylate) and polystyrene nanoparticles (NPs) by mini-emulsion polymerization using AUPDS is investigated, leading to NPs with active ester groups on their surface. By systematically varying reaction parameters and reagent concentrations, it was found that AUPDS feed concentrations between 2–4 mol% yielded narrowly distributed and stable spherical particles with average sizes between 83 and 134 nm for non-cross-linked NPs, and up to 163 nm for cross-linked NPs. By basic hydrolysis of the active ester groups in aqueous dispersion, the positive ζ-potential (ZP) was converted into a negative ZP and charge quantities determined by polyelectrolyte titrations before and after hydrolysis were in the same range, indicating that the active ester groups were indeed accessible in aqueous suspension. Increasing cross-linker amounts over 10 mol% also led to a decrease of ZP of NPs, probably due to internalization of the AUPDS during polymerization. In conclusion, by using optimized reaction conditions, it is possible to prepare active ester functionalized NPs in one stage using AUPDS as a surfmer in mini-emulsion polymerization.

In vitro study of mouse fibroblast tumor cells with TNF coated and Alexa488 marked silica nanoparticles with an endoscopic device for real time cancer visualization

Tumor resection done by minimally invasive procedure owns the challenge of a fast and reliable differentiation between healthy and tumorous tissue. We aim at investigating and developing a method for an intraoperative visualization of tumor cells with functionalized nanoparticles. The goal is to use this technique for the intraoperative use. Our so-called biohybrid systems consist of nanoparticles that are produced by Stober synthesis and coupled with bio active proteins. Such biomimetic nanostructures are capable of imitating the effects of membrane-bound cytokines, which bind to tumor cells for labeling them. A flexible and modular test environment has been developed to evaluate the spraying properties of the particles and to study tissue probes. It enables a fast investigation of different particle configurations and spraying parameters like pressure, spray volume, nozzle geometry, etc.