Electronic band gaps of semiconductors as influenced by their isotopic composition

The present paper focuses on the renormalization effects of the band gaps in the electronic band structure of the elemental semiconductors traced to zero-point vibrations. Electron-phonon interaction and volume changes (in combination with anharmonicity) are the underlying microscopic mechanisms, both dependent on M^−1/2, M being the average isotopic mass. Thus isotopically controlled crystals offer an extraordinary opportunity to test the theoretical predictions with a variety of spectroscopic techniques. The paper discusses the theoretical predictions and their experimental verifications, exploiting derivative and photoluminescence spectroscopy. Illustrative examples on Si and Ge, drawn from the investigations of the authors, are presented.     

Gold nanoparticle–antibody conjugates for specific extraction and subsequent analysis by liquid chromatography–tandem mass spectrometry of malondialdehyde-modified low density lipoprotein as biomarker for cardiovascular risk

Oxidized low-density lipoproteins (OxLDLs) like malondialdehyde-modified low-density lipoprotein (MDA-LDL) play a major role in atherosclerosis and have been proposed as useful biomarkers for oxidative stress. In this study, gold-nanoparticles (GNPs) were functionalized via distinct chemistries with anti-MDA-LDL antibodies (Abs) for selective recognition and capture of MDA-LDL from biological matrices. The study focused on optimization of binding affinities and saturation capacities of the antiMDA-LDL-Ab-GNP bioconjugate by exploring distinct random and oriented immobilization approaches, such as (i) direct adsorptive attachment of Abs on the GNP surface, (ii) covalent bonding by amide coupling of Abs to carboxy-terminated-pegylated GNPs, (iii) oriented immobilization via oxidized carbohydrate moiety of the Ab on hydrazide-derivatized GNPs and (iv) cysteine-tagged protein A (cProtA)-bonded GNPs. Depending on immobilization chemistry, up to 3 antibodies per GNP could be immobilized as determined by ELISA. The highest binding capacity was achieved with the GNP-cProtA-Ab bioconjugate which yielded a saturation capacity of 2.24 ± 0.04 μg mL⁻¹ GNP suspension for MDA-LDL with an affinity K_d of 5.25 ± 0.11 × 10⁻¹⁰ M. The GNP-cProtA-antiMDA-LDL bioconjugate revealed high specificity for MDA-LDL over copper(II)-oxidized LDL as well as native human LDL. This clearly demonstrates the usefulness of the new GNP-Ab bioconjugates for specific extraction of MDA-LDL from plasma samples as biomarkers of oxidative stress. Their combination as specific immunoextraction nanomaterials with analysis by LC–MS/MS allows sensitive and selective detection of MDA-LDL in complex samples.     

A cryogenic underground observatory for rare events: CUORE, an update

CUORE is a proposed tightly packed array of 1000 TeO₂ bolometers, each being a cube 5 cm on a side with a mass of 750 g. The array consists of 25 vertical towers, arranged in a square of 5 towers by 5 towers, each containing ten layers of four crystals. The design of the detector is optimized for ultralow-background searches for neutrinoless double beta decay of ¹³⁰Te (33.8% abundance), cold dark matter, solar axions, and rare nuclear decays. A preliminary experiment involving 20 crystals of various sizes (MIBETA) has been completed, and a single CUORE tower is being constructed as a smaller scale experiment called CUORICINO. The expected performance and sensitivity, based on Monte Carlo simulations and extrapolations of present results, are reported.     

Observation of luminescence from bound multiexciton complexes in gallium doped germanium

Spectrally resolved luminescence associated with the decay of bound multiexciton complexes in optically excited Ge:Ga is observed. This is the first reported observation of multiexciton complexes in p-type germanium. The observed spectra are consistent with the shell model for bound multiexciton complexes.No-phonon, TA, LA, and TO phonon assisted luminescence are observed. From these spectra, the energies of the LA, TA, and TO phonons in Ge:Ga are determined.     

The visible absorption spectrum of NO2: A three-mode nuclear dynamics investigation

The vibronic band origins of the visible absorption spectrum of NO₂ are calculated theoretically with the aid of a simple model Hamiltonian for the coupled electronic and vibrational motions. Including all three vibrational modes in the calculation and using ab initio values of the relevant parameters, we obtain satisfactory qualitative agreement with experiment. In particular, the observed high density and irregular intensity distribution of the band origins is reproduced correctly by the calculation. The present results confirm unambiguosly that the anomalous vibronic structure of the ${}^2\text{B}{}_2\text{←}{}^2\text{A}{}_1$ transition is caused by strong nonadiabatic interactions between the ²B₂ and ²A₁ electronic states of NO₂. They also show that simple deconvolution procedures, which are often used to deperturb irregular spectra, are not applicable to the ${}^2\text{B}{}_2\text{←}{}^2\text{A}{}_1$ transition of NO₂. To further explore the strength of the nonadiabatic effects in NO₂, we calculate the mixing of the different electronic species in the vibronic eigenstates and compare it to several relevant experimental quantities.     

Stereochemie von Metallocenen, 10. Mitt.: Chemische Korrelation von α- und β-substituierten Methylferrocenen; die absolute Konfiguration optisch aktiver, β-substituierter Methyl- und 1.1′-Dimethylferrocene

Zusammenfassung Optisch aktive Methylferrocen-- und--carbonsäuren wurden über die entsprechenden isomeren Methylferroceno[1.2]-cyclohexenone (7, 12 und15, deren Struktur u. a. durchNMR geklärt wurde) und über ein aktives Methylferroceno-cyclohexen (8) bezüglich ihrer Konfigurationen chemische korreliert. ORD-Vergleiche der methylierten Ringketone mit Ferrocenocyclohexenon (10), dessen Konfiguration bekannt war, erlaubten einen sicheren Schluß auf die Konfigurationen aller - und -substituierten Methylferrocene: (1S) für die rechtsdrehenden Säuren und ihre Derivate. Dies konnte auch durch unabhängige Konfigurationsermittlung eines der Ringketone (12) bestätigt werden.Es sind damit die absoluten Konfigurationen von insgesamt 86 optisch aktiven - und -substituierten Ferrocenderivaten bekannt; alle Konfigurationen sind jetzt eindeutig miteinander verknüpft.

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Optically active methylferrocene-- and--carboxylic acids were configurationally correlated by chemical methodsvia the corresponding isomeric methylferroceno[1.2]cyclohexenones (7, 12 and15, the structures of which were elucidated among other methods byNMR) andvia an optically active methylferrocenocyclohexene (8).Comparison of theORD-curves of the methylated ringketones with ferrocenocyclohexenone (10), the configuration of which was known, allowed a reliable conclusion to the configurations of all - and -substituted methylferrocenes: (1S) for the dextrorotatory carboxylic acids and their derivatives. This result could also be confirmed by an independent determination of the configuration of one of the ring ketones (12).Thereby, the absolute configurations of 86 optically active - and -substituted ferrocenederivatives are known; all configurations have now been unambiguously correlated.

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Mit 2 Abbildungen

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9. Mitt. (34. Mitt. über Ferrocenderivate):G. Haller undK. Schlögl, Mh. Chem.98, 603 (1967).     

Synthese von 3-Hydroxy-1-oxo-4-alkyl-1H-benzo[d]pyrido[2,1—b]thiazolen

Zusammenfassung -[Benzothiazolyl-(2)]-acetessigsäurealkylester können zu Benzopyridothiazolen cyclisiert werden. Bei Umsetzung solcher substituierter Acetessigester mit Alkylhalogeniden in Gegenwart von Basen erfolgt Cyclisierung zu Benzopyridothiazolen, die an C-4 alkylsubstituiert sind. IR- und¹H-NMR-Daten dieser Heterocyclen und einiger ihrer Derivate werden mitgeteilt.

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Synthesis of 3-hydroxy-1-oxo-4-alkyl-1H-benzo[d]pyrido-[2.1—b]thiazoles

Ring closure of -[benzothiazolyl-(2)]-acetoacetates affords benzopyridothiazoles. In the reaction of these substituted acetoacetic acid esters with alkyl halides in the presence of bases, the formation of benzopyridothiazoles is observed; these heterocyclic compounds are alkyl-substituted at C-4. IR- and¹H-NMR-spectral data of the benzopyridothiazoles and some of their derivatives are given.

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Aus der DissertationN. Hawlitzky, Freiburg im Breisgau, 1970.