scholarly journals Amplified cross-linking efficiency of self-assembled monolayers through targeted dissociative electron attachment for the production of carbon nanomembranes

2017 ◽  
Vol 8 ◽  
pp. 2562-2571 ◽  
Author(s):  
Sascha Koch ◽  
Christopher D Kaiser ◽  
Paul Penner ◽  
Michael Barclay ◽  
Lena Frommeyer ◽  
...  
Keyword(s):  
Cross Section ◽  
Current Density ◽  
Electron Attachment ◽  
The Other ◽  
Self Assembled Monolayers ◽  
Cross Linking ◽  
Dissociative Electron Attachment ◽  
Electron Dose ◽  
Assembled Monolayers ◽  
The Cross

The determination of the negative ion yield of 2′-chloro-1,1′-biphenyl (2-Cl-BP), 2′-bromo-1,1′-biphenyl (2-Br-BP) and 2′-iodo-1,1′-biphenyl (2-I-BP) upon dissociative electron attachment (DEA) at an electron energy of 0 eV revealed cross section values that were more than ten times higher for iodide loss from 2-I-BP than for the other halogenides from the respective biphenyls (BPs). Comparison with dissociative ionization mass spectra shows that the ratio of the efficiency of electron impact ionization induced fragmentation of 2-I-BP, 2-Br-BP, and 2-Cl-BP amounts to approximately 1:0.7:0.6. Inspired by these results, self-assembled monolayers (SAMs) of the respective biphenyl-4-thiols, 2-Cl-BPT, 2-Br-BPT, 2-I-BPT as well as BPT, were grown on a Au(111) substrate and exposed to 50 eV electrons. The effect of electron irradiation was investigated by X-ray photoelectron spectroscopy (XPS), to determine whether the high relative DEA cross section for iodide loss from 2-I-BPT as compared to 2-Br-BP and 2-Cl-BP is reflected in the cross-linking efficiency of SAMs made from these materials. Such sensitization could reduce the electron dose needed for the cross-linking process and may thus lead to a significantly faster conversion of the respective SAMs into carbon nanomembranes (CNMs) without the need for an increased current density. XPS data support the notation that DEA sensitization may be used to achieve more efficient electron-induced cross-linking of SAMs, revealing more than ten times faster cross-linking of 2-I-BPT SAMs compared to those made from the other halogenated biphenyls or from native BPT at the same current density. Furthermore, the transfer of a freestanding membrane onto a TEM grid and the subsequent investigation by helium ion microscopy (HIM) verified the existence of a mechanically stable CNM created from 2-I-BPT after exposure to an electron dose as low as 1.8 mC/cm2. In contrast, SAMs made from BPT, 2-Cl-BPT and 2-Br-BPT did not form stable CNMs after a significantly higher electron dose of 9 mC/cm2.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Diversity and evolution of stem structure in Eleocharis (Cyperaceae)

Rodriguésia ◽  
2021 ◽  
Vol 72 ◽  
Author(s):  
Jaqueline Priscila Bispo de Almeida Cardoso Marcondes ◽  
Rafael Trevisan ◽  
Maria Cecilia de Chiara Moço ◽  
Cleusa Bona
Keyword(s):  
Cross Section ◽  
Morphological Analysis ◽  
Plant Size ◽  
Molecular Data ◽  
The Other ◽  
Air Gaps ◽  
Ecological Aspects ◽  
The Cross ◽  
Poorly Drained Soils ◽  
Stem Structure

Abstract Eleocharis (Cyperaceae) includes more than 300 species of perennial or annual herbs, frequently found on poorly drained soils. The species are morphologicaly similar, and the taxonomy is difficult because their vegetative and reproductive structures are very reduced. Previous study on the stem architecture in the subgenus Limnochloa showed that anatomical features help in the interpretation of the evolution, taxonomy and ecological aspects of the group. Our objectives were to add new characters from the stem (= culm) structure, to explore the characters in a greater number of Eleocharis species, representatives of the other subgenera, and add these data in a new phylogenetic analysis with molecular data. The study covered 68 species obtained from herbaria and fixed material. In addition to the stem architecture, the internal organization of the tissues, the cross-section format, the presence or absence of stretched cells in aerenchyma air gaps and the plant size were included in the morphological analysis. Our data confirm that spongy aerenchyma pattern is the ancestral condition while the mixed and septate patterns occurred independent and punctually. Only the cross-section format was variable among specimens while the other characters were uniform and relevant for taxonomic use.

scholarly journals Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

2019 ◽  
Vol 15 ◽  
pp. 981-991
Author(s):  
Leon Buschbeck ◽  
Aleksandra Markovic ◽  
Gunther Wittstock ◽  
Jens Christoffers
Keyword(s):  
Quantum Yield ◽  
Lipoic Acid ◽  
Photoelectron Spectroscopy ◽  
Functional Unit ◽  
Gold Surface ◽  
The Other ◽  
Self Assembled Monolayers ◽  
High Signal ◽  
Amidation Reaction ◽  
Assembled Monolayers

Two bifunctional diaminoterephthalate (DAT) fluorescence dyes were prepared in a three-step sequence including one deprotection reaction. One functional unit is α-lipoic acid (ALA) for binding the dye to gold surfaces. It was introduced to the DAT scaffold by an amidation reaction. The other functional unit is a para-(trifluoromethyl)benzyl group for facile detection of the surface-bound material by X-ray photoelectron spectroscopy (XPS). This residue was introduced by reductive amination of the DAT scaffold with the respective benzaldehyde derivative. In one compound (60% yield over three steps) the ALA unit is directly bound to the DAT as a relatively electron-withdrawing amide. In solution (CH2Cl2), this material shows strong fluorescence (quantum yield 57% with emission at 495 nm, absorption maximum at 420 nm). The other compound (57% yield over three steps) possesses a propylene spacer between the ALA and the DAT units for electronic decoupling, thus, bathochromic shifts are observed (absorption at 514 nm, emission at 566 nm). The quantum yield is, however, lower (4%). Self-assembled monolayers on a gold surface of both compounds were prepared and characterized by high-resolution XPS of the C 1s, O 1s, S 2p, N 1s and F 1s emissions. The high signal-to-noise ratios of the F 1s peaks indicated that trifluoromethylation is an excellent tool for the detection of surface-bound materials by XPS.

Absolute cross section for dissociative electron attachment inO2condensed on Kr film

1990 ◽  
Vol 64 (5) ◽  
pp. 523-526 ◽  
Author(s):  
H. Sambe ◽  
D. E. Ramaker ◽  
M. Deschenes ◽  
A. D. Bass ◽  
L. Sanche
Keyword(s):  
Cross Section ◽  
Electron Attachment ◽  
Absolute Cross Section ◽  
Dissociative Electron Attachment

The Bakerian lecture.— On the forms of equipotential curves and surfaces and on lines of flow

1876 ◽  
Vol 24 (164-170) ◽  
pp. 1-32
Keyword(s):  
Cross Section ◽  
Outer Boundary ◽  
The Other ◽  
Curves And Surfaces ◽  
Conducting Wire ◽  
The Wire ◽  
The Cross ◽  
Current Flows ◽  
The One

When any portion of a conducting-wire which joins the two poles of a voltaic battei'y is increased in size, the resistance of the circuit is diminished and a greater current flows through the wire ; and as any increase in the cross section of any portion of the wire causes a corre­sponding increase in the current, it is clear that there is no part of the conducting-wire through which some portion of the current does not flow from the one pole to the other; and the outer boundary of such a wire will be a line of flow. A line of flow is a line drawn in a conductor which indicates at every point of it the direction of the current at that point. A portion of the conductor completely enclosed by lines of flow may be termed a tube of flow.

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