Nanoscale patterning of organosilane molecular thin films from the gas phase and its applications: fabrication of multifunctional surfaces and large area molecular templates for site-selective material deposition

A simple methodology to fabricate micrometer- and nanometer-scale patterned surfaces with multiple chemical functionalities is presented. Patterns with lateral dimensions down to 110 nm were made. The fabrication process involves multistep gas-phase patterning of amine, thiol, alkyl, and fluorinated alkyl-functional organosilane molecules using PDMS molds as shadow masks. Also, a combination process of channel diffused plasma etching of organosilane molecular thin films in combination with masked gas-phase deposition to fabricate multilength scale, multifunctional surfaces is demonstrated.     

Measurement of the sputter yield after mild ion erosion of a pristine Cu(001) surface

Using the STM technique we have determined the sputter yield on a pristine Cu(001) surface after mild (fluence less than 0.044 ions per surface atom) bombardment of the pristine surface with 800 eV Ar⁺ions at normal incidence. The experiments have been performed at substrate temperatures ranging from 200 to 350 K. Making use of the positional correlation of adatoms and surface vacancies, at 200 K and 325 K, we concluded that about 1/3 of the surface adatoms originate from interstitials arriving at the surface and they give a direct indication of the buried bulk vacancies. A careful analysis of the different areas for surface vacancies and adatom then allowed a quantitative evaluation of the sputter yield at 1.2 Cu atoms per 800 eV Ar⁺ ion.     

Local stability of evolutionary attractors for continuous structured populations

In this paper, we are interested in the nonlinear stability of Dirac-type steady solutions to an integro-differential equation appearing in the study of populations which are structured with respect to a quantitative (continuous) trait. We show that stability conditions of Adaptive Dynamics extend to this model.     

An iterated logarithm law for families of Brownian paths

Summary If n is large, a plot of log n independent Brownian paths over [0, n] is nearly certain to give the appearance of a shaded region having square root boundaries.Research of this author was partially supported by the National Science Foundation under grant MCS 82-00786This work was undertaken while B. Schreiber, of Wayne State University, was a Visiting Professor of Mathematics at Michigan State University, whose hospitality he wishes to acknowledge with gratitude.     

Zur Untersuchung von Oliven?l und von Butter

Ohne Zusammenfassung     

Automated on-line gel permeation chromatography-gas chromatography for the determination of organophosphorus pesticides in olive oil

An on-line combination of gel permeation chromatography and gas chromatography has been designed using either a laboratory-built or a commercially available LC-GC apparatus to determine organophosphorus pesticides in olive oil. Gel permeation chromatography was used for sample pretreatment, viz. to separate the low-molecular-mass pesticides from the higher-molecular-mass fat constituents of the oil. A mixture of n-decane and the azeotropic mixture of ethyl acetate and cyclohexane was found to give an adequate separation between the fat and the organophosphorus pesticides. The pesticide-containing fraction, monitored by a UV detector, was transferred on-line to the gas chromatograph using a loop-type interface. n-Decane (6%, v/v) was added to the eluent in order to widen the application range of the transfer technique towards more volatile pesticides. After solvent evaporation through the solvent vapour exit and subsequent GC separation, the compounds were selectively detected with a thermionic or a flame photometric detector. The set-up allowed the direct analysis of oil samples after dilution in the gel permeation chromatography eluent without further sample clean-up. Detection limits were about 5 and 10 μg/kg with the thermionic and the flame photometric detector, respectively, when using an injection volume of only 30 μl of the 20-fold diluted oil. The total procedure was linear in the 0.01–10 mg/kg range for both detectors. For twenty organophosphorus pesticides, the relative standard deviations were 3–13% at the 20–60 μg/kg level.     

Low temperature crystallization behavior of TiO<Subscript>2</Subscript> derived from a sol–gel process

TiO₂ nanoparticles are widely used for many applications and an understanding of the crystallization behavior of TiO₂ is essential, so that heat treatment conditions can be optimized for particular applications. The effect of sol–gel synthesis conditions on the crystallization behavior of TiO₂ has, therefore, been investigated. Complete crystallization to the anatase phase (determined by XRD and TEM analysis) was achieved during drying of the synthesis product at 95 °C. The nanoparticles grew during heat treatment, reaching ∼10–15 nm in diameter with a heat treatment at 450 °C. Explanations are offered for the observed differences in the crystallization and particle growth behavior of TiO₂ synthesized under various conditions.     

Tetrabutylammonium alkyl carboxylate surfactants in aqueous solution: self-association behavior, solution nanostructure, and comparison with tetrabutylammonium alkyl sulfate surfactants

A series of long and ultralong chain tetrabutylammonium alkyl carboxylate (TBACm, TBA = tetrabutylammonium ion; Cm = carboxylate ion C(m-1)H(2)(m-1)CO(2)(-) of total carbon number m) surfactants have been obtained by direct neutralization of the fatty acids with m = 12, 14, 18, 22, and 24 by tetrabutylammonium hydroxide. Time-resolved fluorescence quenching has been used to determine the micelle aggregation number (N) of the surfactants with m = 12, 14, and 18 in the temperature range 10-50 degrees C and of the surfactants with m = 22 and 24 in the temperature range 25-60 degrees C. In all instances the values of N were well below those that can be calculated for the maximum spherical micelle formed by surfactants with the same alkyl chain as the investigated surfactants on the basis of the oil drop model for the micelle core. The microstructure of selected solutions of TBAC22 was examined using transmission electron microscopy at cryogenic temperature and compared to the microstructure of solutions of TBA dodecyl and tetradecyl sulfates. These observations generally confirmed the findings of TRFQ. The self-association behavior of these anionic surfactants with TBA counterions is explained on the basis of the large size and the hydrophobicity of the tetrabutylammonium ions. The important differences in behavior that have been evidenced between tetrabutylammonium alkyl carboxylates and alkyl sulfates are discussed in terms of differences in distribution of the surfactant electrical charge on the headgroup and alkyl chain predicted by quantum chemical calculations (Langmuir 1999, 15, 7546).