Annealing-induced structural transformation of gelatin-capped Se nanoparticles

Selenium nanoparticles were obtained by a new facile synthetic route from gelatin-stabilized aqueous colloidal solutions. The dependence of structural and optical properties of the nanoparticles upon duration of post-synthesis thermal treatment of Se sols was studied by optical absorption, photoluminescence and Raman scattering. We have shown that ageing of colloidal Se solutions at elevated temperatures results in an enlargement and crystallization of selenium nanoparticles, accompanied with noticeable changes in their optical spectra: an enhancement of the photoluminescence of the NPs, incorporated in gelatin films; a “red” shift of both the absorption threshold and emission band maximum; appearance of new peaks in Raman spectra, attributed to the formation of the crystalline phase in the course of the ageing.     

Molecular Engineering of Conjugated Acetylenic Polymers for Efficient Cocatalyst‐free Photoelectrochemical Water Reduction

Conjugated polymers featuring tunable band gaps/positions and tailored active centers, are attractive photoelectrode materials for water splitting. However, their exploration falls far behind their inorganic counterparts. Herein, we demonstrate a molecular engineering strategy for the tailoring aromatic units of conjugated acetylenic polymers from benzene‐ to thiophene‐based. The polarized thiophene‐based monomers of conjugated acetylenic polymers can largely extend the light absorption and promote charge separation/transport. The C≡C bonds are activated for catalyzing water reduction. Using on‐surface Glaser polycondensation, as‐fabricated poly(2,5‐diethynylthieno[3,2‐b]thiophene) on commercial Cu foam exhibits a record H₂‐evolution photocurrent density of 370 μA cm^?2 at 0.3 V vs. reversible hydrogen electrode among current cocatalyst‐free organic photocathodes (1–100 μA cm^?2). This approach to modulate the optical, charge transfer, and catalytic properties of conjugated polymers paves a critical way toward high‐activity organic photoelectrodes.     

Ellipsometric study of the change in the porosity of silica xerogels after chemical modification of the surface with hexamethyldisilazane

Variable angle spectroscopic ellipsometry (VASE) and ellipsometric porosimetry (EP) have been used to study the effect of treatment with hexamethyldisilazane (HMDS) on the porosity of silica xerogel films. Chemical modification of the surface with HMDS was found to reduce the porosity by approximately 15%. This reduction was connected with changes which occur in the silica network, with further condensation or the reaction between neighbouring trimethylsilyl (TMS) surface groups being possible causes.     

Clays and clay minerals: The firing process

⁵⁷Fe Mössbauer spectroscopy reveals changes in iron valence and iron site geometry when clays and clay minerals are heated, and allows a distinction to be made between paramagnetic and magnetically ordered phases. Mössbauer spectra can thus reveal the extent of iron retention in silicate structures upon heating, the identity of iron oxides initially present or formed during the heating process and their transformations, and the character of the atmosphere under which heating was carried out. This makes Mössbauer spectroscopy the most effective tool for the characterization of changes induced by heating phyllosilicates and iron oxides.     

Zur Papyrographie von Carbonamiden

Ohne ZusammenfassungWir danken der Deutschen Forschungsgemeinschaft Bad Godesberg, sowie dem Landesgewerbeamt Baden-Württemberg, Stuttgart, für die Unterstützung der vorliegenden Arbeit.     

Untersuchungen an Kollagen

Zusammenfassung Die Reaktion von Kollagen mit verschiedenen p-Nitrophenylestern wurde untersucht. Schrumpfungstemperaturen, Quellung, Säurebindungskapazität, enzymatischer Abbau durch Papain sowie die quantitative Bestimmung der wasserlöslichen DNP-Aminosäuren zeigen, daß Malonsäure-bis-(p-nitrophenyl)-ester nicht vernetzend reagiert, während die entsprechenden Ester von Kohlen- bzw. Thiokohlensäure gute Quervernetzungsreagenzien sind. Oxalsäure-(p-nitrophenyl)-ester ist zu schwer löslich, um damit Reaktionen durchführen zu können.10. Mitteilung über Kollagen und 5. Mitteilung über Nitrophenylester. 9. Mitteilung über Kollagen vgl.J. Schnell undH. Zahn, Makromolekulare Chem. (im Druck); 4. Mitteilung über Nitrophenylester vgl.H. Zahn, H. K. Rouette undF. Schade (im Druck). Kurzfassung eines Teils der vorliegenden Arbeit in: Abstracts of Papers, 6th International Congress of Biochemistry, S. 179 (New York 1964).Die vorliegende Arbeit wurde vom Landesamt für Forschung beim Ministerpräsidenten des Landes Nordrhein-Westfalen, Düsseldorf, in dankenswerter Weise gefördert. Die Sehnenkollagenfolie wurde uns von Dr. Emil Braun, Firma C. Freudenberg, Weinheim, freundlicherweise überlassen.     

Präzisions-Massenbestimmungen mit dem elektrischen Massenfilter

The construction of an electric quadrupole spectrometer for precision mass determinations in the regionA>130 is described. The hyperbola-shaped electrodes are formed by sets of wires. A method is discussed which reduces the measurement of a mass ratio to a measurement of the ratio of two resistors. In contrast to the conventional ‘peak matching’ technique, in this method the intensity ratio of both members of a dublett occurs as an additional parameter and has to be measured. For testing, measurements were done on Xe-isotopes. The mass ratios obtained are:¹³²Xe/¹³¹Xe=1.007 632 1 ±5,¹³⁴Xe/¹³²Xe=1.015 730. The intensity ratio of¹³²Xe/¹³¹Xe is 0.7872±0.0020. These values are in good agreement with the most accurate measurements of Nier's laboratory.     

Die β-Zerfallsenergie der Technetiumisotope Tc103, Tc104 und Tc105

Molybdenum fission products from Uranium were rapidly separated using a sublimation technique. Their Technetium daughters could be separated from the Molybdenum sample by a second sublimation. The decay of Tc¹⁰³, Tc¹⁰⁴ and Tc¹⁰⁵ was investigated using scintillation counters and coincidence methods. Tc¹⁰³ decays by the emission of twoβ-groups at energies of 2·0 Mev and 2·2 Mev followed byγ-lines of 135 kev, 215 kev and 350 kev. According to a proposed decay-scheme Tc¹⁰³ decays with aQ-value of 2·35±0·10 Mev into Ru¹⁰³. Tc¹⁰⁵ emits aβ-group of about 3·4 Mev maximum energy followed by a 110 kevγ-transition. TheQ-value of the Tc¹⁰⁵ decay was estimated to be 3·4±0·2 Mev. Fromβ?γ- andγ?γ-coincidence spectra of Tc¹⁰⁴ fourβ?γ-γ-cascades could be identified, which populate excited states of 0·36 Mev, 0·89 Mev, 2·5 Mev, 3·5 Mev and 4·05 Mev in Ru¹⁰⁴. TheQ-value of the Tc¹⁰⁴ decay was found to be 5·85±0·10 Mev. TheQ-values and spin assignements of the groundstates of Tc¹⁰³ and Tc¹⁰⁵ are discussed in a more detailedβ-decay systematic.     

Carbobenzoxy-l-nitrotyrosyl-glycyl-dl-alanin-benzylester

Zusammenfassung Beim Azidieren von Carbobenzoxy-l-tyrosyl-glycin-hydrazid mit überschüssigem Nitrit wird der Phenolkern des eingebauten Tyrosins nitriert und bei der Reaktion des nitrierten Azids mitdl-Alanin-benzylester das Nitropeptidderivat erhalten.Mit 2 Abbildungen Fritz Wessely zum 60. Geburtstag in Verehrung gewidmet.