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101.
Haojie Zhang Dirk J. Hagen Xiaopeng Li Andreas Graff Frank Heyroth Bodo Fuhrmann Ilya Kostanovskiy Stefan L. Schweizer Francesco Caddeo A. Wouter Maijenburg Stuart Parkin Ralf B. Wehrspohn 《Angewandte Chemie (International ed. in English)》2020,59(39):17172-17176
Transition‐metal phosphides (TMP) prepared by atomic layer deposition (ALD) are reported for the first time. Ultrathin Co‐P films were deposited by using PH3 plasma as the phosphorus source and an extra H2 plasma step to remove excess P in the growing films. The optimized ALD process proceeded by self‐limited layer‐by‐layer growth, and the deposited Co‐P films were highly pure and smooth. The Co‐P films deposited via ALD exhibited better electrochemical and photoelectrochemical hydrogen evolution reaction (HER) activities than similar Co‐P films prepared by the traditional post‐phosphorization method. Moreover, the deposition of ultrathin Co‐P films on periodic trenches was demonstrated, which highlights the broad and promising potential application of this ALD process for a conformal coating of TMP films on complex three‐dimensional (3D) architectures. 相似文献
102.
Dr. Santosh K. Singh Jesse La Jeunesse Vasant Vuppuluri Prof. Steven F. Son Dr. Bing-Jian Sun Mr. Yue-Lin Chen Prof. Agnes H. H. Chang Prof. Alexander M. Mebel Prof. Dr. Ralf I. Kaiser 《Chemphyschem》2020,21(9):837-842
Understanding of the fundamental mechanisms involved in the decomposition of 1,3,5-trinitro-1,3,5-triazinane (RDX) still represents a major challenge for the energetic materials and physical (organic) chemistry communities mainly because multiple competing dissociation channels are likely involved and previous detection methods of the products are not isomer selective. In this study we exploited a microsecond pulsed infrared laser to decompose thin RDX films at 5 K under mild conditions to limit the fragmentation channels. The subliming decomposition products during the temperature programed desorption phase are detected using isomer selective single photoionization time-of-flight mass spectrometry (PI-ReTOF-MS). This technique enables us to assign a product signal at m/z=42 to ketene (H2CCO), but not to diazomethane (H2CNN; 42 amu) as speculated previously. Electronic structure calculations support our experimental observations and unravel the decomposition mechanisms of RDX leading eventually to the elusive ketene (H2CCO) via an exotic, four-membered ring intermediate. This study highlights the necessity to exploit isomer-selective detection schemes to probe the true decomposition products of nitramine-based energetic materials. 相似文献
103.
Zhenghai Yang Chao He Srinivas Doddipatla Vladislav S. Krasnoukhov Prof. Valeriy N. Azyazov Prof. Alexander M. Mebel Prof. Ralf I. Kaiser 《Chemphyschem》2020,21(17):1898-1904
The methylgermylene species (HGeCH3; X1A′) has been synthesized via the bimolecular gas phase reaction of ground state methylidyne radicals (CH) with germane (GeH4) under single collision conditions in crossed molecular beams experiments. Augmented by electronic structure calculations, this elementary reaction was found to proceed through barrierless insertion of the methylidyne radical in one of the four germanium-hydrogen bonds on the doublet potential energy surface yielding the germylmethyl (CH2GeH3; X2A′) collision complex. This insertion is followed by a hydrogen shift from germanium to carbon and unimolecular decomposition of the methylgermyl (GeH2CH3; X2A′) intermediate by atomic hydrogen elimination leading to singlet methylgermylene (HGeCH3; X1A′). Our investigation provides a glimpse at the largely unknown reaction dynamics and isomerization processes of the carbon-germanium system, which are quite distinct from those of the isovalent carbon system thus providing insights into the intriguing chemical bonding of organo germanium species on the most fundamental, microscopic level. 相似文献
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107.
We have undertaken the molecular imprinting of Leu5-enkephalin, and derivatives related to this endogenous neuropeptide, in highly cross-linked methacrylic acid/ethylene dimethacrylate copolymers. The underivatized enkephalin peptide yielded polymers with poor recognition abilities, since the imprinting of this compound had to be performed using dimethyl sulfoxide, which was found to interfere with the imprint inducement, as the solvent of polymerisation. In order to circumvent this problem, the amino- and carboxy-protected derivatives Boc-Leu5-enkephalin and Leu5-enkephalin anilide, which are soluble in apolar solvents, were investigated as alternative imprint molecules. Both compounds led to polymers which are highly specific for the imprint species. The anilide derivative was shown to be a good substitute for the free peptide since the resultant polymers showed efficient recognition of the parent enkephalin structure. 相似文献
108.
Soft single-photon ionisation (SPI)–time-of-flight mass spectrometry (TOFMS) has been used to investigate the effect of different
cigarette-lighting devices on the chemical composition of the mainstream smoke from the first cigarette puff. Lighting devices
examined were a Borgwaldt electric lighter, a propane/butane gas lighter, a match, a candle, and the burning zone of another
cigarette. To eliminate the effects of the different masses of tobacco burnt by use of the different lighting methods a normalisation
procedure was performed which enabled investigation of changes in the chemical patterns of the resulting smoke. When another
cigarette was used as the lighting device, elevated levels of ammonia and other nitrogen-containing substances were observed.
These are high in the sidestream smoke of the cigarette used for lighting and would be drawn into the mainstream smoke of
the cigarette being lit. In contrast, smoke from the cigarette lit by the electric lighter contained slightly higher normalised
amounts of isoprene. Lighting the cigarette by use of a candle resulted in larger amounts of substances, e.g. benzene, which
most probably originated from thermal decomposition of wax. The composition of the first puff of smoke obtained by use of
the three lighting methods with open flames (gas lighter, match, and candle) was usually similar whereas the composition of
the smoke produced by use of the electric lighter and the cigarette as the lighter were more unique. The chemical patterns
generated by the different lighting devices could, however, be separated by principal-component analyses. Two additional test
series were also studied. In the first the cigarette was lit with an electric lighter, then extinguished, the ash was cut
off, and the cigarette was re-lit. In the second the cigarette was heated in an oven to 80 °C for 5 min before being lit.
These treatments did not result in changes in the chemical composition compared with cigarettes lit in the ordinary way.
Figure Time-of-flight mass spectrometry (TOFMS) has been used to investigate the effect of different cigarette-lighting devices on
the chemical composition of the mainstream smoke from the first cigarette puff 相似文献
109.
David Uhrig Ralf Schlegel Roland Weidisch Jimmy MaysAuthor vitae 《European Polymer Journal》2011,(4):560-568
The synthesis of well-defined multigraft copolymers having a polydiene backbone with polystyrene side chains is briefly reviewed, with particular focus on controlling branch point spacing and branch point functionality. Use of living anionic polymerization and chlorosilane linking chemistry has led to the synthesis of series of materials having regularly spaced trifunctional (comb), tetrafunctional (centipede), and hexafunctional (barbwire) branch points. The morphologies of these materials were characterized by transmission electron microscopy and small-angle X-ray scattering, and it was found that the morphologies were controlled by the local architectural asymmetry associated with each branch point. Mechanical properties studies revealed that such multigraft copolymers represent a new class of thermoplastic elastomers (TPEs) with superior elongation at break and low residual strains as compared to conventional TPEs. 相似文献
110.