Atomic force microscopy study of the adsorption and electrostatic self-organization of poly(amidoamine) dendrimers on mica

The adsorption behavior of poly(amidoamine) dendrimers to mica surfaces was investigated as a function of ionic strength and pH. The conformation and lateral distribution of the adsorbed dendrimers of generations G8 and G10 were obtained ex situ by tapping mode atomic force microscopy (AFM). The deposition kinetics of the dendrimers was found to follow a diffusion-limited process. Fractional surface coverage and pair correlation functions of the adsorbed dendrimers were obtained from the AFM images. The data are interpreted in terms of the random sequential adsorption (RSA) model, where electrostatic repulsion due to overlapping double layers is considered. Although the general trends typical for an RSA-determined process are well-reproduced, quantitative agreement is lacking at low ionic strengths.     

Square‐Planar Carbonylchlororhodium(I) Complexes Containing trans‐Spanning Diphosphine Ligands as Catalysts for the Carbonylation of Methanol

The rhodium(I) complexes trans‐[Rh(diphos)(CO)Cl] 7 (diphos=pbpb), 8 (diphos=nbpb), and 9 (diphos=cbpb) were synthesized (Scheme 4) and used as catalysts for the carbonylation of MeOH to AcOH (Scheme 1). The trans coordination imposed by the rigid C‐spacer framework of the diphos ligands pbpb, nbpb, and cbpb, demonstrated by ³¹P‐NMR and IR spectroscopy of 7 – 9 and unambiguously confirmed by single‐crystal X‐ray structure analysis of 7 , improved the thermal stability of the rhodium(I) system under carbonylation conditions and, hence, the catalytic performance of the complexes. For the catalytic carbonylation of MeOH, the active catalyst could be prepared in situ from the mixture of [Rh(CO)₂Cl]₂ and the corresponding diphos ligand pbpb, nbpb, or cbpb, giving the same results as carbonylation in the presence of the isolated complexes 7, 8 or 9 (see Table). The highest activity was observed for complex 7 (or the mixture [Rh(CO)₂Cl]₂/pbpb, the catalytic turnover number (TON) being 950 after 15 min (170°, 22 bar).     

Gitterpunkte in Lemniskatenscheiben

Let G (R) denote the number of lattice points (,) **Z² in the domain B(R) bounded by the lemniscate (x²+y²)²=2R² (x²–y²) and put P(R)=G(R)-R²(R² being the area of B(R)). The purpose of this paper is to determine the order of magnitude of P(R) for large R by proving the asymptotic relation (3). An analogous result is given for the eight curve x⁴=R² (x²–y²).     

Wismutmonojodid BiJ,eine Verbindung mit Bi(O) und Bi(II)

Bismuth Monoiodide, a Compound with Bi(O) and Bi(II) Bismuth monoiodide was synthesized in closed tubes from the elements as well as from Bi and HgI₂ as a black coloured crystalline compound. With increasing temperature BiI passes two transitions. α-BiI is stable below 370 K and changes to β-BiI by a martensitic transition. γ-BiI is the stable modification above 564 K and decomposes at 585 K peritectically to BiI₃ and a lower iodide. All three modification crystallize in the monoclinic space group C2/m. The structures (single crystal studies) of α-BiI and β-BiI are characterized by onedimensional infinite chains [Bi₄I₄] with covalent bonds but only weak interactions in between. The [Bi₄I₄]-chains are built up by two completely different Bi atoms. Bi(A) is only bonded to three Bi whereas Bi(B) has bonds to one Bi and four I. The average bond lengths are Bi? Bi = 304.5 pm and Bi? I = 313.7 pm respectively. The configuration of the Bi(A) atoms is typical for Bi^O and that one of the Bi(B) atoms is characteristic for Bi²⁺ with the electron configuration s²p¹. Therefore, α-BiI and β-BiI are mixed valence compounds [Bi^OBi²⁺I₄]. The structures are variants of the simple cubic polonium type of structure and differ in the stacking of connected units. The structures and their transitions, the possible configurations for monohalides BiX on principle as well as the energy balances of the disproportionation of Bi⁺ are discussed together in detail.     

Efficient cross-coupling of functionalized arylzinc halides catalyzed by a nickel chloride-diethyl phosphite system

[reaction: see text] The combination of diethyl phosphite and DMAP as ligands for nickel in an 8:1 THF-N-ethylpyrrolidinone (NEP) mixture allows a very efficient cross-coupling reaction to be performed between various functionalized arylzinc halides and aryl bromides, triflates and activated chlorides. The reaction proceeds at 25 degrees C within 1-48 h and requires only 0.05 mol % of the nickel catalyst.     

Relativistic all-electron configuration interaction calculations on the gold atom

We present the results of relativistic and non-relativistic self-consistent field and configuration interaction calculations for the gold atom, using the spin-free no-pair Hamiltonian in a basis set expansion. A new basis set for the gold atom is discussed and its results in relativistic and non-relativistic self-consistent field calculations are compared to those of numerical Dirac-Hartree-Focic and Hartree-Fock calculations, respectively. Excitation energies, electron affinities and ionization potentials were calculated using a multi-reference configuration interaction technique and are in reasonable agreement with experiment in the relativistic case.     

Templating S100A9 amyloids on Aβ fibrillar surfaces revealed by charge detection mass spectrometry,microscopy, kinetic and microfluidic analyses

The mechanism of amyloid co-aggregation and its nucleation process are not fully understood in spite of extensive studies. Deciphering the interactions between proinflammatory S100A9 protein and Aβ₄₂ peptide in Alzheimer''s disease is fundamental since inflammation plays a central role in the disease onset. Here we use innovative charge detection mass spectrometry (CDMS) together with biophysical techniques to provide mechanistic insight into the co-aggregation process and differentiate amyloid complexes at a single particle level. Combination of mass and charge distributions of amyloids together with reconstruction of the differences between them and detailed microscopy reveals that co-aggregation involves templating of S100A9 fibrils on the surface of Aβ₄₂ amyloids. Kinetic analysis further corroborates that the surfaces available for the Aβ₄₂ secondary nucleation are diminished due to the coating by S100A9 amyloids, while the binding of S100A9 to Aβ₄₂ fibrils is validated by a microfluidic assay. We demonstrate that synergy between CDMS, microscopy, kinetic and microfluidic analyses opens new directions in interdisciplinary research.

Templating mechanism of S100A9 amyloids on Aβ fibrillar surfaces during amyloid co-aggregation process was revealed by synergy of biophysical methods including charge detection mass spectrometry, microscopy, kinetic and microfluidic analyses.     

Preparation and Characterisation of Nano-Structured WO<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> Layers for Photoelectrochromic Devices

Nano-structured WO₃-TiO₂ layers were prepared by the sol-gel route. To obtain transparent, porous and crack free layers up to 0.8 μ m with a single dipping cycle a templating strategy was used. As a template three-dimensionally network based on organically modified silane was introduced to the WO₃ and TiO₂ sols. The WO₃ layers were dip-coated onto the conductive glass substrate (TCO) and the TiO₂ layers on the top of the WO₃ layer. The morphology and the structure of the layers were determined by Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HR-TEM), Energy Dispersive X-Ray Spectroscopy (EDXS), Auger and Infrared spectroscopy. SEM image of the WO₃-TiO₂ layer confirmed the nano-porosity of the layers and give the size of the particles of about 10 nm for TiO₂ and 30 nm for WO₃ layer. Further analysis indicated that the titanium sol penetrates the WO₃ layer. Particles in the WO₃ layer consist of a crystalline monoclinic WO₃ core surrounded by a 5–10 nm amorphous phase consisting of WO₃, TiO₂ and SiO₂. The WO₃-TiO₂ layers were used to assemble all solid state photoelectrochromic (PE) devices. Under 1 sun irradiation (1000 W/m²) the visible transmittance of the PE device changes from 62% to 1.6%. The colouring and bleaching processes last about 10 minutes.