Rearrangement of Langmuir-Blodgett stearic acid films and band assignments in deuterated stearic acid monolayers

Band assignments in the C-D stretching region of straight chain hydrocarbon species are derived from the spectra of stearic acid monolayers on gold. The fatty acid molecules reorient with respect to the metal surface as the films age. Correlating the changes in the IR spectra of both the undeuterated and deuterated acids allows one to identify the vibrational modes of the latter based on the accepted assignments of the former. The CD₂ asymmetric and symmetric stretches are observed at 2194 and 2086 cm^–1, respectively. Bands at 2212 and 2221 cm^–1 are attributed to asymmetric in-plane and out-of-plane CD₃ stretches. Assignments of several other features in this region are given while one band remains unassigned.     

Synthesis of a heterodinuclear ruthenium(II)–platinum(II) complex linked by l-cysteine methyl ester

A potential anticancer heterodinuclear ruthenium(II)–platinum(II) complex, [ruthenium(II)(4,4′-dimethyl-2,2′-bipyridine)₂(5-(l-cysteine-methyl ester)-1,10-phenanthroline)-trans-chlorodiammineplatinum(II)] chloride, [Ru(Me₂bipy)₂(5-(l-cysteine-Me)-phen)-trans-Pt(NH₃)₂Cl]Cl₃, was synthesised. l-Cysteine methyl ester was used to link the two metal centres, as more conventional straight chain diaminoalkanes and 2-mercaptoethylamine failed to couple to the phenanthroline ligand. From the precursor mononuclear ruthenium(II) complexes, which were separated into their Δ- and Λ-isomers by column chromatography, the dinuclear complex was synthesised and characterised by ¹H and ¹³C NMR, UV–Vis, circular dichroism, fluorescence and electrospray ionisation mass spectrometry.     

An investigation of misfit dislocations in Al on (001) GaAs grown by chemical beam epitaxy

We report a transmission electron microscope study of the morphology and interfacial structure of Aluminium grown on (001) GaAs by chemical beam epitaxy (CBE). The Al grows in islands for all thicknesses deposited, and exhibits four distinct orientation relationships with respect to the substrate. One of these orientation relationships becomes dominant as growth progresses, with (011)_Al parallel to (001)_GaAs. Misfit dislocations can be seen in the interface between this orientation and the substrate with Burgers vector 1/4(110)_GaAs, and a crystallographic analysis shows that these dislocations are associated with interfacial steps of height 1/2[001]_GaAs. In (001)Al on (001)GaAs, the existence of these dislocations has in the past been regarded as evidence for the existence of a rigid-body shift of the Al in the interfacial plane. Using cross-sectional high-resolution TEM, it is shown that this shift is not present in the (011) orientation. The similarity in the microstructure and crystallography of the (001) and (011) orientations leads us to suggest that there is also no shift in (001) Al on (001)GaAs. This is in conflict with previous investigations of this system using a wide variety of techniques.     

Energy relaxation time between macroscopic quantum levels in a superconducting persistent-current qubit

We measured the intrawell energy relaxation time tau(d) approximately 24 micros between macroscopic quantum levels in the double well potential of a Nb persistent-current qubit. Interwell population transitions were generated by irradiating the qubit with microwaves. Zero population in the initial well was then observed due to a multilevel decay process in which the initial population relaxed to lower energy levels during the driven transitions. The decoherence time, estimated from tau(d) within the spin-boson model, is about 20 micros for this configuration with a Nb superconducting qubit.     

Electrochemically Predicting Phenolic Substrates’ Suitability for Detection by Amperometric Laccase Biosensors

In this article, a rapid, simple method of electrochemically predicting a given phenolic substrate’s ability to be detected via amperometric laccase biosensors is proposed. Ten selected substrates were analysed by cyclic voltammetry and the relevant electrochemical parameters compared to biosensor kinetic parameters produced through amperometric detection of these substrates. The two major findings of this study were that biosensor detection sensitivities were found to correlate to: (1) peak oxidation potential of a substrate at unmodified electrodes and (2) the apparent Michaelis? Menten constant, K_m, of the biosensor‐substrate system, once corrections accounting for the relative differences in electroreducible product yield are made.