排序方式: 共有19条查询结果,搜索用时 31 毫秒
1.
Debye-Hückel theory of mixed charged-zwitterionic lipid layers 总被引:1,自引:0,他引:1
2.
The article describes how solar ultraviolet-A radiation can be used to digest samples as needed for voltammetric ultratrace determination of uranium(VI) in river water. We applied adsorptive stripping voltammetry (AdSV) using chloranilic acid as the complexing agent. Samples from the river Warnow in Rostock (Germany) were pretreated with either soft solar UV or wit artificial hard UV from a 30-W source emitting 254-nm light. Samples were irradiated for 12?h, and both methods yielded the same results. We were able to detect around 1?μg·L?1 of uranium(VI) in a sample of river water that also contained dissolved organic carbon at a higher mg·L?1 levels. No AdSV signal was obtained for U(VI) without any UV pre-treatment. Pseudo-polarographic experiments confirmed the dramatic effect of both digestion techniques the the AdSV response. The new method is recommended for use in mobile ultratrace voltammetry of heavy metals for most kinds of natural water samples including tap, spring, ground, sea, and river waters. The direct use of solar radiation for sample pre-treatment represents a sustainable technique for sample preparation that does not consume large quantities of chemicals or energy. Figure
Adsorptive stripping voltammetry response of uranium(VI) in a) Original Sample b) 6?h Solar UV Sample, c) 12?h Solar UV Sample, and d) 6?h UV Sample with standard additions of 2, 4 and 6?μg?L-1. Potentials are given vs. Ag/AgCl (3?M KCl). 相似文献
3.
Muhammad Nazrul Islam Burak Aksu Mehmet Güncü Markus Gallei Metin Tulu Tarik Eren 《Journal of polymer science. Part A, Polymer chemistry》2020,58(6):872-884
Bacterial infection is a global problem, especially resistance acquired by bacteria against to antibiotics; there is urgent need for the development of antibiotics. Here, we proposed dendron-grafted polymers via ring opening metathesis polymerization (ROMP) featuring different with tailored hydrophobicity/hydrophilicity and cationic charges. Dendritic oxanorbornene derivatives were synthesized having two and six carbon linkers and their corresponding random and block copolymers were prepared having pendant pyridinium salt moieties via ROMP. In total, 12 different water-soluble dendronized cationic polymers featuring hexyl pyridinium moieties were prepared and investigated. Six carbon linker possessing triple charge density and hexyl pyridinium functionality each repeating unit copolymers exhibited high antibacterial activity against Gram-positive bacteria (S. aureus). However, all the polymers were inactive against Gram-negative bacteria (E. coli). Most of the copolymers are non-hemolytic (>HC 50 = 1,000 μg/ml). It was also observed that, there is no significant effect between block copolymers and random copolymers keeping hydrophobicity and cationic charge density constant. Zeta potential was measured to investigate the mechanism in solution via the interaction of polymers with S. aureus, while scanning electron microscope (SEM) measurements image confirms damage of the bacterial cell wall after implementation of biocidal polymer. 相似文献
4.
Concerted Determination of the Hydrogen Atom and Electron Transfer Capacity of Lipid Soluble Reducing Agents 下载免费PDF全文
Solomon Mengistu Lemma Matteo Scampicchio Andrea Bulbarello Marco Mason Loni Schweikert 《Electroanalysis》2014,26(7):1582-1587
This paper describes a method based on square wave voltammetry to evaluate either the electron transfer or the hydrogen atom transfer of lipid soluble antioxidants such as dl ‐mix‐tocopherol, BHT, ethoxyquin and retynil acetate. The electron transfer (ET) capacity was evaluated by the peak current, peak potential and the area under the anodic wave, whereas the hydrogen atom transfer (HAT) capacity by the kinetic rate of the reaction between antioxidants and 2,2‐Azobis(2‐methylpropionamidine) dihydrochloride (AAPH). The results indicate that ethoxyquin and tocopherol have the highest ET and HAT capacity. However, HAT capacity of tocopherol, BHT and retinyl acetate depend on the concentration. The approach has the advantage to assess HAT and ET capacity of lipid soluble antioxidant in a single concerted protocol. 相似文献
5.
Naz Mohammed Aghatabay Metin Tulu Yaghub Mahmiani Mehmet Somer Basaran Dulger 《Structural chemistry》2008,19(1):71-80
1,6-Bis(benzimidaz-2-yl)-3,4-dithiahexane ligand (L) and its mercury halide complexes were prepared and characterised. The
elemental analysis, molecular conductivity, FT-Raman, FT-IR (mid, far), 1H, 13C NMR and geometry optimization in MOPAC using MNDOd parameter on CACHE, prove the existence of neutral, mononuclear and the
distorted tetrahedral [Hg(L)X2] complexes. In all the three complexes, the ligand acts as a chelating bidentate, through two of the bridging sulphur atoms
and together with the monodentate coordination of the two anionic halide ligands to the metal centre forming a possible 4-coordinate
compounds. The antimicrobial activities of free ligand, its hydrochlorinated salt, mercury halides and the complexes are evaluated
using disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method,
against 10 bacteria. The obtained results from disk diffusion method are assessed in side-by-side comparison with those of
Penicillin-g, Ampicillin, Cefotaxime, Vancomycin, Oflaxacin and Tetracyclin well-known antibacterial agents. The results from
dilution procedure are compared with Gentamycin as antibacterial and Nystatin as antifungal. The antifungal activities are
reported on five yeast cultures namely Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii and Hanseniaspora guilliermondii, and the results are referenced with Nystatin, Ketaconazole and Clotrimazole, commercial antifungal agents. In most cases,
the compounds show broad-spectrum (Gram+ & Gram− bacteria) activities that are comparatively, slightly less active or equipotent to the antibiotic and antifungal agents in
the comparison tests. 相似文献
6.
Naz Mohammed Aghatabay Metin Tulu Mehmet Somer Durata Haciu Ayberk Yilmaz 《Structural chemistry》2008,19(1):21-32
1,3-bis(benzimidazol-2-yl)-2-thiapropane (L) ligand and its zinc halide ZnX2 (X = Cl, Br, I) complexes have been synthesized. The compounds were characterized using the elemental analysis, molar conductivity,
FT-Raman, FT-IR (mid i.r., far i.r.), 1H and 13C NMR spectra, and quantum chemical calculations performed with Gaussian 03 package program set. The optimized geometries
and vibrational frequencies of the ligand and [Zn(L)Cl2] complex were calculated using the DFT/B3LYP method with a 6–31g(d) basis set. The geometry optimization of [Zn(L)Cl2] yields a slightly distorted tetrahedral environment around Zn ion, while the molecule clearly reveals the Cs symmetry. The
molar conductivity data reveals that the complexes are neutral. The ligand is bidentate, via two of the imine nitrogen atoms
in the bis-imidazole ring units, and together with the monodentate coordination of the two halides to the metal centre. 相似文献
7.
DK Rai G Beaucage EO Jonah DT Britton S Sukumaran S Chopra GG Gonfa M Härting 《The Journal of chemical physics》2012,137(4):044311
Nanomaterials with disordered, ramified structure are increasingly being used for applications where low cost and enhanced performance are desired. A particular example is the use in printed electronics of inorganic conducting and semiconducting nanoparticles. The electrical, as well as other physical properties depend on the arrangement and connectivity of the particles in such aggregate systems. Quantification of aggregate structure and development of structure∕property relationships is difficult and progress in the application of these materials in electronics has mainly been empirical. In this paper, a scaling model is used to parameterize the structure of printed electronic layers. This model has chiefly been applied to polymers but surprisingly it shows applicability to these nanolayers. Disordered structures of silicon nanoparticles forming aggregates are investigated using small angle x-ray scattering coupled with the scaling model. It is expected that predictions using these structural parameters can be made for electrical properties. The approach may have wide use in understanding and designing nano-aggregates for electronic devices. 相似文献
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9.
Teramage Mengistu T. Sun Xinchao 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):233-244
Journal of Radioanalytical and Nuclear Chemistry - The ambient dose rate (ADR) in a coniferous forest floor contaminated by Fukushima-derived 137Cs was calculated for small temporal scale as a... 相似文献
10.
Mengistu TZ Goel V Horton JH Morin S 《Langmuir : the ACS journal of surfaces and colloids》2006,22(12):5301-5307
Chemical force titrations-plots of the adhesive force between an atomic force microscope tip and sample as a function of pH-were acquired on alkyl monolayer-derivatized Si(111) surfaces. Gold-coated AFM tips modified with thioalkanoic acid self-assembled monolayers (SAM) were employed. Alkyl monolayer-derivatized Si(111) surfaces terminated with methyl, carboxyl, and amine groups were produced via hydrosilylation reactions between 1-alkene reagents and H-terminated silicon. The functionalized surfaces were characterized using standard surface science techniques (AFM, FTIR, and XPS). Titration of the methyl-terminated surface using the modified (carboxyl-terminated) atomic force microscope tip resulted in a small pH-independent hydrophobic interaction. Titration of the amine-terminated surface using the same tip resulted in the determination of a surface pKa of 5.8 for the amine from the pH value from the maximum in the force titration curve. A pK(1/2) of 4.3 was determined for the carboxyl-terminated Si(111) in a similar way. These results will be discussed in relation to the modified Si(111) surface chemistry and organic layer structure, as well as with respect to existing results on Au surfaces modified with SAMs bearing the same functional groups. 相似文献