Chemical bath deposition of SnO2 and Cd2SnO4 thin films

A new approach of chemical bath deposition (CBD) of SnO₂ thin films is reported. Films with a 0.2 μm thickness are obtained using the multi-dip deposition approach with a deposition time as little as 8–10 min for each dip. The possibility of fabricating a transparent conducting oxide layer of Cd₂SnO₄ thin films using CBD is investigated through successive layer deposition of CBD-SnO₂ and CBD-CdO films, followed by annealing at different temperatures. High quality films with transmittance exceeding 80% in the visible region are obtained. Annealed CBD-SnO₂ films are orthorhombic, highly stoichiometric, strongly adhesive, and transparent with an optical band gap of ～4.42 eV. Cd₂SnO₄ films with a band gap as high as 3.08 eV; a carrier density as high as 1.7 × 10²⁰ cm^?3; and a resistivity as low as 1.01 × 10^?2 Ω cm are achieved.     

A first low‐resolution difference Fourier map of phosphorus in a membrane protein from near‐edge anomalous diffraction

Crystal diffraction of three membrane proteins (cytochrome bc₁ complex, sarcoplasmic reticulum Ca²⁺ ATPase, ADP‐ATP carrier) and of one nucleoprotein complex (leucyl tRNA synthetase bound to tRNAleu, leuRS:tRNAleu) was tested at wavelengths near the X‐ray K‐absorption edge of phosphorus using a new set‐up for soft X‐ray diffraction at the beamline ID01 of the ESRF. The best result was obtained from crystals of Ca²⁺ ATPase [adenosin‐5′‐(β,γ‐methylene) triphosphate complex] which diffracted out to 7 Å resolution. Data were recorded at a wavelength at which the real resonant scattering factor of phosphorus reaches the extreme value of ?20 electron units. The positions of the four triphosphates of the monoclinic unit cell of the ATPase have been obtained from a difference Fourier synthesis based on a limited set of anomalous diffraction data.     

Absorption spectra of human skin in vivo in the ultraviolet wavelength range measured by optoacoustics

Knowledge of the optical properties of human skin in the ultraviolet range is fundamental for photobiologic research. However, optical properties of human skin in the ultraviolet spectral range have so far mainly been measured ex vivo . We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3 nm steps using laser optoacoustics. In this technique, optical properties are derived from the pressure profile generated by absorbed light energy in the sample. In a study on 20 subjects belonging to phototypes I–IV, we studied the optical properties at the volar and dorsal aspect of the forearm as well as on the thenar. Analysis of the measured absorption spectra shows that comparable skin areas—like different sides of the forearm—have qualitatively similar optical characteristics. Still, the optical properties may vary substantially within the same area, probably due to the skin structure and inhomogeneities. Comparison of the spectra from different skin sites indicates that the spectral characteristics of the stratum corneum and its chromophores play an important role for the optical properties of human skin in vivo in the ultraviolet B range.     

Investigations on mechanical properties of PI-PS multigraft copolymers

The stress-strain behaviour of multigraft copolymers consisting of a polyisoprene (PI) backbone and grafted polystyrene (PS) arms have been characterized by applying models of rubber elasticity such as Mooney-Rivlin, slip-tube and the extended non-affine tube model. Additionally, the range of low deformation has been investigated by relaxation tests for determining the stress relaxation. Multigraft copolymers show high strain at break and low residual strain caused by the large number of physical cross links resulting from several grafted PS side chains. From the model fits the material parameters and of the slip-tube model, representing the influence of chemical cross links and entanglements effects, respectively, and the n_e/T_e-value (n_e - number of statistical segments between two successive entanglements, T_e - Langley trapping factor) of the extended non-affine tube model, are used to describe the tensile behaviour of these thermoplastic elastomers. The PS content was considered as filler phase taking into account the effect of hydrodynamic amplification. The influence of functionality and the number of branch points per molecule on the strain at break and the tensile strength is explained by the model parameters describing the stress-strain curve at low to medium (?400%, slip-tube, Mooney-Rivlin) and low to high (?900%, extended non-affine tube) elongations. It was observed that for the material with a spherical morphology is increasing with the number of branch points β (each branch point consists of a PI backbone segment, depending on the functionality one, two or four grafted PS arms). For cylindrical and lamellar morphologies the was decreasing with increasing β, which could be reconfirmed by applying the extended non-affine tube model where the n_e/T_e-parameter is increasing with β.     

Fulvalenediyl-bridged heterobimetallic complexes consisting of sandwich and half-sandwich compounds with early-late transition metals

A straightforward synthesis methodology for the preparation of heterobimetallic [(η⁵-C₅H₅)(η⁵-C₅H₄-C₅Me₄)M] (3a, M = Fe; 3b, M = Ru) and [(η⁵-C₅H₅)((μ-η⁵:η⁵-C₅H₄-C₅Me₄)TiCl₃)M] (4a, M = Fe; 4b, M = Ru) in which early and late transition metals are connected by a fulvalenediyl bridge is reported.The structures of molecules 3b and 4a in the solid state are discussed. Most noteworthy in 4a is the exo arrangement of the iron and titanium atoms coordinated by the fulvalenediyl unit which itself is twisted with a dihedral angle between the joined cyclopentadienyl rings of 19.33(9)°. Electrochemical, UV/Vis/NIR spectroscopic and spectroelectrochemical experiments on 4a and Cp∗TiCl₃, for comparison, provide evidence for some transfer of electronic information between the conjoined ferrocene and half-sandwich titanocene trichloride subunits of 4a. Evidence comes from systematic potential shifts and the presence of a fairly intense Fe → Ti charge-transfer absorption band that vanishes upon oxidation and reduction of 4a.     

Simultaneous determination of particle size and refractive index by time-resolved Mie scattering

With this numerical study we have investigated the pulse-induced and time-resolved Mie scattering with the aim of determining the size and the refractive index of transparent spherical particles simultaneously. The temporal interval between the scattering light signals of two different orders of scattered light allows only particle sizing. But if it is possible to detect three different orders of scattered light, then we have two independent time intervals. This situation is given if the detector has a position about θ=90°. With these scattering angle signals of reflection and refraction of 1st and 3rd order appear with approximately the same intensity. Then the numerical quotient of the two temporal intervals between these scattering orders is a function of the refractive index only. We have calculated these specific quotients by models of geometric optics for 1.1≤m≤1.6 and 75°≤θ≤90° and have seen that there is a very high agreement with the results of time-resolved Mie calculations.     

A spin-selective approach for surface states at Co nanoislands

During recent years the surface electronic states of cobalt nanoislands grown on Cu(111) and Au(111) have been extensively studied and still yield fascinating results. Among magnetic surfaces, cobalt islands are particularly appealing because of their spin-polarized electronic states near the Fermi energy, involving localized d states of minority character, as well as free-like s–p states of majority character. We show here that these states are a sensitive probe to minute changes of structural details such as strain and stacking, and therefore constitute an ideal playground to study the interplay between structural and spin-related properties. Due to their size, cobalt islands on Cu(111) offer the additional opportunity to host single-magnetic adsorbates suitable for spin-polarized scanning tunneling microscopy and spectroscopy (SP-STM and SP-STS). We establish here that, in an energy interval just below the Fermi level, the spin-polarization of a transition-metal atom is governed by surface-induced states opposite in sign compared to the island, while the spin-polarization of Co-Phthalocyanine molecules is governed by molecular states. This opens up interesting perspectives for controlling and engineering spin-polarized phenomena at the nanoscale.     

Cysteine‐Selective Phosphonamidate Electrophiles for Modular Protein Bioconjugations

We describe a new technique in protein synthesis that extends the existing repertoire of methods for protein modification: A chemoselective reaction that induces reactivity for a subsequent bioconjugation. An azide‐modified building block reacts first with an ethynylphosphonite through a Staudinger‐phosphonite reaction (SPhR) to give an ethynylphosphonamidate. The resulting electron‐deficient triple bond subsequently undergoes a cysteine‐selective reaction with proteins or antibodies. We demonstrate that ethynylphosphonamidates display excellent cysteine‐selective reactivity combined with superior stability of the thiol adducts, when compared to classical maleimide linkages. This turns our technique into a versatile and powerful tool for the facile construction of stable functional protein conjugates.     

Ultrasensitive Detection of Salmonella and Listeria monocytogenes by Small‐Molecule Chemiluminescence Probes

Detection of Salmonella and L. monocytogenes in food samples by current diagnostic methods requires relatively long time to results (2–6 days). Furthermore, the ability to perform environmental monitoring at the factory site for these pathogens is limited due to the need for laboratory facilities. Herein, we report new chemiluminescence probes for the ultrasensitive direct detection of viable pathogenic bacteria. The probes are composed of a bright phenoxy‐dioxetane luminophore masked by triggering group, which is activated by a specific bacterial enzyme, and could detect their corresponding bacteria with an LOD value of about 600‐fold lower than that of fluorescent probes. Moreover, we were able to detect a minimum of 10 Salmonella cells within 6 h incubation. The assay allows for bacterial enrichment and detection in one test tube without further sample preparation. We anticipate that this design strategy will be used to prepare analogous chemiluminescence probes for other enzymes relevant to specific bacteria detection and point‐of‐care diagnostics.     

Influence of liquid layers on energy absorption during particle impact

The influence of the thickness of a covering liquid layer and its viscosity as well as the impact velocity on energy loss during the normal impact on a flat steel wall of spherical granules with a liquid layer was studied. Free-fall experiments were performed to obtain the restitution coefficient of elastic-plastic γ- Al2O3 granules by impact on the liquid layer, using aqueous solutions of hydroxypropyl methylcellulose with different concentrations for variation of viscosity （1-300 mPa s）, In the presence of a liquid layer, increase of liquid viscosity decreases the restitution coefficient and the minimum thickness of the liquid layer at which the granule sticks to the wall. The measured restitution coefficients were compared with experiments performed without liquid layer. In contrast to the dry restitution coefficient, due to viscous losses at lower impact velocity, higher energy dissipation was obtained, A rational explanation for the effects obtained was given by results of numerically solved force and energy balances for a granule impact on a liquid layer on the wall. The model takes into account forces acting on the granule including viscous, surface tension, capillary, contact, drag, buoyancy and gravitational forces. Good agreement between simulations and experiments has been achieved.