Fluorescence interference-contrast microscopy on oxidized silicon using a monomolecular dye layer

A silicon chip is covered by a monomolecular film of a fluorescence dye with silicon dioxide used as a spacer. The fluorescence depends on the distance of the dye from the silicon. The modulation of the intensity is described quantitatively by an optical theory which accounts for interference of the exciting light and of the emitted light. The effect is used to obtain a microscopic picture of the surface profile with a precision of a few Angströms. The perspectives for an application in wet systems such as neuron-silicon junctions and lipid membranes on silicon are pointed out.     

Exposure of [MnIII6CrIII]3+ single-molecule magnets to soft X-rays: The effect of the counterions on radiation stability

X-ray absorption spectroscopy studies of the [Mn^III₆Cr^III]³⁺ single-molecule magnet deposited as a microcrystalline layer on gold substrates are presented. The oxidation state of the manganese centers changes from Mn^III to Mn^II due to irradiation with soft X-rays. The influence of the charge-neutralizing anions on the stability of [Mn^III₆Cr^III]³⁺ against soft X-ray exposure is investigated for the different anions tetraphenylborate (BPh₄^?), lactate (C₃H₅O₃^?) and perchlorate (ClO₄^?). The exposure dependence of the radiation-induced reduction process is compared for [Mn^III₆Cr^III]³⁺ with the three different anions.     

Mechanosynthesis of spinel ferrite nanoparticles followed by Mössbauer spectroscopy

The single-step synthesis of nanosized MgFe₂O₄ and NiFe₂O₄ via mechanochemical processing of binary oxide precursors is followed by ⁵⁷Fe Mössbauer spectroscopy. Quantitative information is provided on both ionic and spin configurations in mechanosynthesized spinels. The response of the mechanosynthesized ferrite nanoparticles to changes in temperature is also studied.     

A rapid and precise method for determination of D/H ratios of plant methoxyl groups

Stable hydrogen isotope ratio measurements of specific plant components are increasingly used in numerous fields of research, including sample origin verification and climate research. A recently suggested method with considerable potential in this context is the D/H isotope ratio (δ²H value) analysis of plant matter methoxyl groups. The method entails ether or ester cleavage with hydriodic acid (HI) to form the gaseous compound methyl iodide (CH₃I) and measurement of the δ²H value of this gas. Here we describe a method for the rapid and precise δ²H analysis of plant matter methoxyl groups using gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/P/IRMS). The conditions for sample preparation were investigated for isotope discrimination effects, the GC conditions were optimized, the reproducibility of the measurement of standards was studied, and the precision of the method was defined. The reproducibility of δ²H values determined for a CH₃I standard on 20 consecutive measurements was found to be 2‰. The method was also tested on four methoxyl‐rich plant components: vanillin, lignin, wood and pectin. The analytical precision obtained, when expressed as the average standard deviation for these compounds, was better than 1.6‰. The described method is rapid, allowing preparation and analysis of a sample within 1 h, and produces accurate and reproducible isotopic measurements. Copyright © 2008 John Wiley & Sons, Ltd.