Effect of Composition on Surface Properties of Polydimethylsiloxane-based Inorganic/Organic Hybrid Films

Surface properties of the polydimethylsiloxane (PDMS)-based inorganic/organic hybrids films prepared from silanol-terminated PDMS and titanium tetra-isopropoxide (TIP) were investigated with an aim at the application to the thermal-fixation roll for electro-photographic printers. The 300°C-treated hybrid film with the PDMS/TIP molar ratio of 0.5 exerted a relatively high contact angle of water as 115°C. It was found by using Tapping-Mode Atomic Force Microscopy (AFM) that the hybrid film surface changed from lamella structure to sea-island structure with the increase of PDMS content when heat-treated at 150°C, and became homogenous surface over 300°C. The phase-shift detected by AFM was negative shift, showing that hybrid surface became more hydrophobic as the PDMS/TIP molar ratios of 0.35 and 4.0 exhibited excellent toner-offset property of showing no adhesion of toners, suggesting their practical use in the photographic printers.     

Strategies to vectorize conventional SCF-Cl algorithms

Recent high-performance computers, especially supercomputers, achieve very high-speed operations but bring about serious I/O problems in quantum chemical computations. Strategies to vectorize conventional SCF-CI algorithms are discussed relating to the I/O problems. The conventional SCF-CI algorithm which is proposed here reduces I/O processing by eliminating all sorting routines and redundant integral files and generates directly nonzero and nonredundant PK integrals with a vectorizable canonically-ordered list. The new implementation has been undertaken and successfully realized as a program system named GSCF3. The vector to scalar acceleration rate of GSCF3 on the HITAC S-810 are as follows: 2.5 5 in the AO integral evaluation, 5 12 in the SCF calculation, 15 30 in the four-index integral transformation, 10 20 in the CI matrix diagonalization, and overall 510 through SCF-CI.     

Disjoining pressure and stratification in asymmetric thin-liquid films

We directly measure, for the first time, disjoining pressure isotherms for asymmetric oil/aqueous surfactant/gas (i.e., pseudoemulsion) films using a modified version of the porous-plate technique first developed by Mysels in conjunction with thin-film interferometry. Dynamic film-thinning experiments are also performed on individual foam and pseudoemulsion films. At SDS surfactant concentrations above the critical micelle concentration (CMC) (0.1 M SDS), the pesudoemulsion films exhibit the same step-wise layer thinning observed in foam films under similar conditions. Further, we conduct dynamic thinning experiments on solid/liquid/gas systems and show that aqueous 0.2 M CTAB films sandwiched between glass and air also display discrete thinning transitions. All of these stratification transitions arise from oscillations in the disjoining pressure isotherm, generated by amphiphilic structuring within the film.For 0.1 M SDS dedecane/air pesudoemuslion films, the slope and peak height of the disjoining-pressure oscillations increase with each subsequent amphiphilic layer as film thickness decreases. Magnitudes of the structural forces are low (<100 Pa) but the length scale of the oscillations is large (10 nm) and rathe far reaching (50 nm). Moreover, for 0.1 M SDS solutions, the capillary pressures associated with film rupture are significantly lower for pseudoemulsion films (0.1 kPa) when compared to foam films (15 kPa) at equivalent conditions. Taken together, our dynamic thinning and equilibrium disjoining pressure measurements indicate that stratification in 0.1 M SDS films has little effect on both kinetic and thermodynamic films stability.     

Simple screening method for the fast determination of clenbuterol in animal feeds

Summary A simple method for the determination of clenbuterol is described. It is extracted from the sample at pH 3 and then at pH 11, followed by partitioning the analyte into water at pH 3 and reextraction into ethyl acetate at pH 9. Clenbuterol is oxidized with KMnO₄ to clenbuteron for GC-determination. Recoveries for 0.01– 1.0 mg/kg were between 70% and 110% (standard deviation ±14%, n = 18).

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Eine einfache Screening-Methode zur schnellen Bestimmung von Clenbuterol in tierischen Futtermitteln

     

Donorstärken in 1,2-Dichloräthan

Zusammenfassung Kalorimetrische und spektrophotometrische Untersuchungen über die Donorstärke einer Anzahl nicht-wäßriger Lösungsmittel zeigen, daß die relative Reihung der Donorstärken unabhängig von der Natur des Akzeptors ist. Die Donorreihung lautet gegenüber SbCl₅, Jod und Phenol folgendermaßen: Pyridin > Dimethylsulfoxid > Dimethylacetamid Dimethylformamid > > Trimethylphosphat Diphenylphosphoroxychlorid > Diäthyläther > Aceton > Propandiol-1,2-carbonat > Acetonitril > > Selenoxychlorid Phosphoroxychlorid Benzoylchlorid > > Thionylchlorid > Sulfurylchlorid.

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Calorimetric and spectrophotometric work on the donor strength of various non-aqueous solvents have shown that the relative order of donor strength is independent from the nature of the acceptor. The order of donor strength towards SbCl₅, I₂ and phenole is pyridine > dimethylsulfoxide > dimethylacetamide dimethylformamide > trimethylphosphate diphenylphosphonic chloride > diethyl ether > acetone > propane diol-1,2-carbonate > acetonitrile > selenium oxychloride phosphorus oxychloride benzoyl chloride > thionyl chloride > sulfuryl chloride.

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Mit 1 Abbildung     

Fabrication and Characterization of Sol-Gel GeO2-SiO2Erbium-Doped Planar Waveguides

GeO2-SiO2 sol-gel planar waveguides doped with Er were deposited by spinning on silica substrates. P2 O5 or Al2O3 were used as co-dopants to improve erbium dissolution in the GeO2-SiO2 matrix. Multilayer amorphous films were obtained at 600 or 700°C.Er ions in the planar waveguide pumped at 980 nm showed fluorescence features around 1530 nm. Narrow fluorescence spectra (20 nm) and long lifetimes (6 ms) were found in P2O5 co-doped samples, whereas Al2O3 co-doping gave wider spectra (50 nm) with slightly lower lifetimes (5 ms). The quenching concentration in the Al2O3 co-doped samples was 0.9 mol% Er.Heat treatments in CCl4 improve the active properties and the addition of Yb enhances the pump absorption efficiency.     

Preparation and Characterization of Germanium Sulfide Based Sol-Gel Planar Waveguides

Germanium sulfide based glass films have been deposited by spin-coating onto single crystal silicon wafers and silica glass disks, using the reaction between GeCl₄, either pure or doped with of 5 mol% of SbCl₃, dissolved in toluene, with H₂S. The films, heat-treated under different conditions, were characterized by X-ray diffraction, infrared spectroscopy, X-ray photoemission spectroscopy, mechanical profilometry and ellipsometry. Oxide contamination was found in these films, but this was reduced or even eliminated by a heat-treatment in H₂S gas, at 270°C. A maximum film thickness of 1.3 m was achieved and the refractive indices of the films were in the range of 1.9–2.8 at 633 nm. Propagated light was observed by butt-coupling, for waveguides deposited on silica glass disks, at = 633 nm. Optical losses in the range of 1.1–1.9 dB/cm were measured at this wavelength, for different regions of different planar waveguides. The present method has achieved reasonably low loss and low levels of oxide contamination, which are promising for active applications.     

Experimental investigation on tritium gettering with hydrogen uranyl phosphate (HUP)

At room-temperature and atmospheric pressure, using electrode disks of various sizes, under the action 4 7Vdc eletric field, we gettered tritium gas from 2.2L of air containing (0.15 18.61)×10⁸ Bq of tritium and (3000 12000) ppm of moisture during 50 hours or so the efficiency of gettering tritium was over 95%. Applying liquid scintillation counting method, we measured the tritium in the disks after gettering, and found that the amounts of tritium in the disks were equal to those reduced in the tested tritiated air.     

Enthalpy of Solution of Squalane in Alcohols

Enthalpy of solution at 25°C of squalane in butyl alcohols and 1-octanol is determined calorimetrically. The endothermic effect of dissolution increases in the order 1-OctOH < BuOH < i-BuOH < t-BuOH. A linear correlation is found between the enthalpies of solution of squalane and hexadecane, from which the enthalpy of solution of squalane in methanol is determined. The contributions of the cavity formation and solute-solvent interaction to the enthalpy of solution are estimated by multiple regression analysis. The enthalpy of cavity formation is only slightly dependent on the length of the main chain of an alcohol and also on the branching type, varying in the order 1-OctOH BuOH i-BuOH < MeOH s-BuOH < t-BuOH. Interaction of squalane with alcocols increases in the order MeOH < t-BuOH < BuOH < i-BuOH s-BuOH < 1-OctOH.     

Study of free volume parameters of polystyrenes of different molecular architecture by positron annihilation lifetime measurement

Differences of size, content and size distribution of free volumes in linear branched and three-armed polystyrenes, synthesized by radical and anionic processes, were observed by positron annihilation lifetime measurements. The temperature dependence of an average free volume radius was quite similar among polystyrenes of different architectures and molecular weight distributions. The free volume radius increased with temperature, from 0.27 nm (T:60 K) to 0.29 nm (T:260 K) and 0.30 nm (T _g:363 K), then to 0.35 nm (423 K), showing turning at and transition temperature. The free volume content decreased from 60 K to 220 K to 300 K showing peculiar minimum at 220 K to 300 K depending on the molecular shape, increased above 320 K, upto 340 to 360 K. The free volume contents decreased with an increase of molecular weight and by an addition of oligomer or plasticiser, suggesting differences in relaxation time or molecular motion between the edge and middle portions of molecular chain and filling effect of smaller molecules in free volumes, respectively. The apparent free volume fraction showed clear variations atT andT _g. Size distribution of free volumes suggested more complicated behavior of free volume upon the molecular relaxations and filling effect.     

Production of poly(methyl methacrylate) particles by dispersion polymerization with mercaptopropyl terminated poly(dimethylsiloxane) stabilizer in supercritical carbon dioxide

Poly(methyl methacrylate) (PMMA) particles were produced by dispersion polymerization of methyl methacrylate in the presence of mercaptopropyl terminated poly(dimethylsiloxane) (MP-PDMS) in supercritical carbon dioxide at about 30 MPa for 24 h at 65 °C. The particle diameter could be controlled in a size range of submicron to micron by varying MP-PDMS concentration. The MP-PDMS worked as not only a chain transfer agent but also a colloidal stabilizer, which was named tran stab.Part CCLI of the series Studies on suspension and emulsion     

Gamma radiolysis of Methyl Red solution and reaction induced by γ-irradiated NaCl in Methyl Red

The -radiolysis of Methyl Red solution in HCl medium at pH=2 has been studied along with energy transfer reaction brought about byF and hole centers of -irradiated NaCl. The G-values for degradation of the azo dye indicator by radiolysis and -irradiated salt were determined as 9·10^–1 and 4.8·10^–3, respectively. The kinetic rate constants (k) of degradation are evaluated as 2·10^–5 rad^–1 in the case of direct radiolysis, while for the irradiated salt it is 2·10^–7 rad^–1. The extent of degradation by direct -radiolysis is 100–200 times greater as compared to that by the -irradiated salt. The same mechanism is proposed for radiolysis as well as the reaction induced by -irradiated sodium chloride.     

Tail-end purification of americium from plutonium loading effluents using a mixture of octyl (phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide and tri-N-butyl phosphate

The tail-end purification of Am from Pu loading effluents in 7.5M HNO₃ containing 160 mg l^–1 Am and 1.2 mg l^–1 Pu has been carried out. With 0.2M CMPO+1.2M TBP in dodecane as the extractant and stripping by 0.04M HNO₃+0.05M NaNO₂, the Pu level is brought down to 31.2 g l^–1. When the acidity was reduced to 4.2M HNO₃, one contact with 20% TLA/dodecane and subsequent extraction by a mixture of CMPO and TBP and stripping with 0.04M HNO₃+0.05M NaNO₂ gave Am samples without any detectable amounts of Pu. The recovery of Am was 90% by the first procedure and 98% by the second one.     

Reversible Optical Sensor Membrane for Hydrogen Peroxide Using an Immobilized Fluorescent Probe,and its Application to a Glucose Biosensor

An optical sensor for hydrogen peroxide (HP) based on the probe europium tetracycline (EuTc) incorporated into a polyacrylonitrile-co-polyacrylamide polymer matrix is described. Upon optical excitation with 400-nm light, the EuTc in the membrane displays fairly strong fluorescence peaking at 616nm. The fluorescence intensity increases up to 3-fold if the sensor is exposed to solutions containing HP. The effect is reversible and can thus be used for continuous sensing. The largest signal changes with HP are observed at pH levels between 6.5 and 7.5, and the range of the response is between 10 and 300ppm (w/w) of HP, equal to 0.3 to 10mmolL^–1). At concentrations above 0.3% of HP, decomposition of the EuTc in the membrane is observed. The limit of detection is 15ppm (0.45mmolL^–1). The response is fully reversible and rather slow (10min) in both directions, but the reverse response may be accelerated by addition of a reducing agent such as thiosulfate. Alkali ions and most anions remain inert, but phosphate and citrate interfere, as do Cu²⁺ ions, which quench fluorescence. In order to image the spatial distribution of HP concentrations, sensor membranes were placed on the bottom of the wells of a microtiter plate, and their fluorescence was imaged using an LED-based device based on the measurement of the luminescence decay time of EuTc. If glucose oxidase is immobilized on the sensor layer, a glucose sensor is obtained in which the HP sensor acts as the transducer and which can quantify glucose in concentrations between 0.1 and 5mmolL^–1. The limit of detection for glucose is 0.2mmolL^–1.     

Insertion of 3d- and 4f-Elements into Silver Iodide

The interaction of manganese and some 4f-metals (M) with silver iodide is studied. The samples are obtained by sputtering M onto the surface of polycrystalline AgI films (0.2 m, 300 K) in a vacuum. Optical absorption in the samples is interpreted as the insertion of M ions into AgI with the formation of dopants AgI:M. A new phase with an optical bandgap of 3.7 eV emerges in the samples with elevated concentrations of La, Ce, Pr, Nd, Sm, or Dy (n _M/n _Ag 0.1). X-ray diffraction patterns for such samples with Sm correspond to structures with large interfacial distances, for example, 0.99, 0.87, 0.76, and 0.67 nm. In air, AgI forms in the samples with a new phase; this process is hindered by the sputtered protective coatings. According to optical absorption data, X-ray diffraction, and local microanalysis the Mn insertion into AgI is followed by the formation of a new phase (2Ag:Mn:4I), which may belong with solid electrolytes Ag₂MI₄, where nonmagnetic M are known (Zn, Cd, Sn, Hg, Pb).     

Microscopic Parameters of Heterostructures with Ge Nanoclusters and Thin Films in a Si Matrix

Microstructural parameters (interatomic distances, coordination numbers, and their anisotropy) of heterostructures with Ge nanoclusters and thin films were determined by EXAFS spectroscopy. The variation of these parameters is correlated to the morphology of the germanium quantum points on Si(001), and adequate structural models are suggested. It is found that the pseudomorphic four-monolayer germanium films buried in a Si matrix contain up to 50% Si atoms. The pyramidal germanium islands (lateral size 15 nm, height 1.5 nm) formed during further Stranski–Krastanov heteroepitaxial growth have a thinner Ge–Si intermediate boundary layer near two monolayers and Ge–Ge interatomic distances 0.04 shorter than those in pure germanium in agreement with the results of bond length calculations in the framework of the valence force field (VFF) model.     

Photolithographic Patterning and Doping of Silica Xerogel Films

This study shows that conventional photolithography can be applied for patterning native or organic dye-doped silica films (0.5 m thick) obtained via a base-catalyzed sol-gel process. Photoresist was spin-coated onto high optical quality xerogel films, soft-baked, exposed to UV irradiation through a photomask, and developed with a commercial photoresist developing solution. Etching away of the photoresist-unprotected areas of the silica films was carried out with a dilute HF solution, while the remaining unexposed photoresist was removed with acetone. Interdigitated array patterns with features as small as 0.5 mm show a smooth surface and extremely sharp interfaces. Densification of the films at 550°C for 2 h decreases the film thickness by 11%, increases the refractive index from 1.420 to 1.456, and allows for well-defined patterning down to length scales of 10 m. Since the densification conditions are incompatible with organic dopants, it is demonstrated that sol-gel films can be doped after pattering (post-doping) by adsorption of cationic dyes from solution. Scanning electron microscopy reveals that the microstructure of patterned sol-gel films is similar to that of bulk monoliths, indicating that the photolithographic procedure is not harmful to the film quality. All patterned films demonstrate highly regular light diffraction patterns.     

Role of Water on Fast Proton Conduction in Sol-Gel Glasses

Fast proton-conducting P2O5-ZrO2-SiO2 glasses were prepared by sol-gel processing of metal alkoxides. Glasses heated to 150 to 400°C exhibited room temperature conductivities of 10–4 S/cm, larger by 2 order of magnitude than that of as-prepared gel, 3 × 10–7 S/cm at 30°C. The conductivity increased quadratically with the increasing product of proton and molecular water concentration. These high conductivities were regarded as fast proton transfer accelerated by molecular water bonded with the hydroxyl groups.     

X-Ray Spectroscopic Investigation of the Zr-Site in Thin Film Sol-Gel Surface Preparations

X-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) measurements were made on thin film (1000 Å) sol-gel adhesion promoting surface treatments. These silicon/zirconium-containing sol-gel coatings are possible replacement processes for traditional surface preparations that use environmentally undesirable and potentially toxic materials. The sol-gels were waterborne mixtures formulated with tetra-n-propoxyzirconium (TPOZ) and a silane, either 3-glycidoxypropyl-trimethoxysilane (GTMS) or 3-aminopropyl-triethoxysilane (APS). Results show that dried sol-gel powders formulated with TPOZ or TPOZ + GTMS have longer Zr—O bond lengths (2.18 Å, CN 7 or 8) than the TPOZ + silane + metal substrate samples (2.10 Å, CN 6). The fraction (+/– 0.10) of Zr in a short bonded 6-fold site is highest (0.80) for TPOZ + (APS or GTMS) on (Ti or Al), at an intermediate value (0.40) for TPOZ on Ti and low (0.10) for the powders. For sol-gels deposited on a metal substrate, there are indications of a chemical bond between the thin film sol-gel and the metal substrate. The TPOZ + APS coatings on Ti data suggest that this Zr—O—Ti bond is present with a Zr—Ti separation of 3.5 Å. Only subtle differences were observed in the near-neighbor bonding due to curing treatment variations from room temperature to 125°C, alloy substrate variations (Ti-6Al-4V/Al 2024), and age of the deposited sol-gel coating (up to 1 year).     

On the use of a dead-time meter for pile-up corrections

Correction for pile-up losses in the amplifier is possible by the dead-time fraction indicator of the ADC in case of long-lived radionuclides. If the dead-time meter has been calibrated, an accuracy of 1.5% is feasible up to a dead-time fraction of 25%. The precision decreases from 1.5% at 10% dead-time fraction to 3% at a deadtime fraction of 30%.