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991.
E. Marin F. Boschetto M. Zanocco W. Zhu T. Adachi N. Kanamura T. Yamamoto B.J. McEntire E.N. Jones C. Powell J. Hendry R.M. Bock B.S. Bal G. Pezzotti 《Materials Today Chemistry》2021
Most structural bioceramics are comprised of metallic oxides such as alumina and zirconia. They are generally considered to be completely bioinert, but a non-oxide ceramic, silicon nitride, achieves equivalent levels of mechanical reliability while being bioactive. Silicon nitride can not only stimulate cellular proliferation but it is also antipathogenic with demonstrated efficacy against Gram-positive and Gram-negative bacteria, fungi, and viruses. In this work, three physical vapor deposition coatings with different Si:N ratios (silicon-rich, stoichiometric, and nitrogen-rich) were deposited on mirror-polished silica glass substrates. The coatings were characterized by spectroscopic and microscopic techniques and tested in vitro against E. coli and KUSA-A1 mesenchymal cells. Results showed that nitrogen-enriched SixNy has a strong antibacterial effect against E. coli and contributes to cellular proliferation while silicon-enriched SixNy stimulates the production of bone tissue, with higher indexes for mineralization and quality. These results suggest that SixNy's biological properties can be optimized for specific applications by carefully tuning its surface chemistry. 相似文献
992.
Krystyna Maslowska-Jarzyna Maria L. Korczak Jakub A. Wagner Micha J. Chmielewski 《Molecules (Basel, Switzerland)》2021,26(11)
Owing to their strong carbazole chromophore and fluorophore, as well as to their powerful and convergent hydrogen bond donors, 1,8-diaminocarbazoles are amongst the most attractive and synthetically versatile building blocks for the construction of anion receptors, sensors, and transporters. Aiming to develop carbazole-based colorimetric anion sensors, herein we describe the synthesis of 1,8-diaminocarbazoles substituted with strongly electron-withdrawing substituents, i.e., 3,6-dicyano and 3,6-dinitro. Both of these precursors were subsequently converted into model diamide receptors. Anion binding studies revealed that the new receptors exhibited significantly enhanced anion affinities, but also significantly increased acidities. We also found that rear substitution of 1,8-diamidocarbazole with two nitro groups shifted its absorption spectrum into the visible region and converted the receptor into a colorimetric anion sensor. The new sensor displayed vivid color and fluorescence changes upon addition of basic anions in wet dimethyl sulfoxide, but it was poorly selective; because of its enhanced acidity, the dominant receptor-anion interaction for most anions was proton transfer and, accordingly, similar changes in color were observed for all basic anions. The highly acidic and strongly binding receptors developed in this study may be applicable in organocatalysis or in pH-switchable anion transport through lipophilic membranes. 相似文献
993.
Fast and selective analytical methods help to ensure the chemical identity and desired purity of the prepared complexes before their medical application, and play an indispensable role in clinical practice. Mass spectrometry, despite some limitations, is an integral part of these methods. In the context of mass spectrometry, specific problems arise with the low ionization efficiency of particular analytes. Chemical derivatization was used as one of the most effective methods to improve the analyte’s response and separation characteristics. The Schotten–Baumann reaction was successfully adapted for the derivatization of ESI hardly ionizable Re(VII) bis(catechol) oxochlorocomplex. Various alkyl and halogen p-substituted anilines as possible derivatization agents were tested. Unlike the starting complex, the reaction products were easily ionizable in electrospray, providing structurally characteristic molecular and fragment anions. DFT computer modeling, which proposed significant conformation changes of prepared complexes within their deprotonation, proved to have a close link to MS spectra. High-resolution MS and MS/MS measurements complemented with collision-induced dissociation experiments for detailed specification of prepared complexes’ fragmentation pathways were used. The specified fragmentation schemes were analogous for all studied derivatives, with an exception for [Re(O)(Cat)2PIPA]. 相似文献
994.
Kim Glootz Antoine Barthlemy Ingo Krossing 《Angewandte Chemie (International ed. in English)》2021,60(1):208-211
The earth‐metal olefin complex [Ga I (COD)2]+[Al(ORF)4]? (COD=1,5‐cyclooctadiene; RF=C(CF3)3) constitutes the first homoleptic olefin complex of any main‐group metal accessible as a bulk compound. It is straight forward to prepare in good yield and constitutes an olefin complex of a main‐group metal that—similar to many transition‐metals—may adopt the +1 and +3 oxidation states opening potential applications. Crystallographic‐, vibrational‐ and computational investigations give an insight to the atypical bonding between an olefin and a main‐group metal. They are compared to classical transition‐metal relatives. 相似文献
995.
Ionic liquids (ILs) are considered to be one of the steppingstones to fabricate next generation electrochemical devices given their unique physical and chemical properties. The addition of water to ILs significantly impact electrochemical related properties including viscosity, density, conductivity, and electrochemical window. Herein we utilize ambient pressure X-ray photoelectron spectroscopy (APXPS) to examine the impact of water on values of the electrochemical shift (S), which is determined by measuring changes in binding energy shifts as a function of an external bias. APXPS spectra of C 1s, O 1s and N 1s regions are examined for the IL 1-butyl-3-methylimidazolium acetate, [C4mim][OAc], at the IL/gas interface as a function of both water vapor pressure and external bias. Results reveal that in the absence of water vapor there is an IL ohmic drop between the working electrode and quasi reference electrode, giving rise to chemical specific S values of less than one. Upon introducing water vapor, S values approach one as a function of increasing water vapor pressure, indicating a decrease in the IL ohmic drop as the IL/water mixture becomes more conductive and the potential drop is driven by the electric double layer at the electrode/IL interface. 相似文献
996.
Damien Mahaut Dr. Aurélien Chardon Loïc Mineur Prof. Guillaume Berionni Prof. Benoît Champagne 《Chemphyschem》2021,22(19):1958-1966
The activation or heterolytic splitting of methane, a challenging substrate usually restricted to transition metals, has so far proven elusive in experimental frustrated Lewis pair (FLP) chemistry. In this article, we demonstrate, using density functional theory (DFT), that 1-aza-9-boratriptycene is a conceptually simple intramolecular FLP for the activation of methane. Systematic comparison with other FLP systems allows to gain insight into their reactivity with methane. The thermodynamics and kinetics of methane activation are interpreted by referring to the analysis of the natural charges and by employing the distortion-interaction/activation strain (DIAS) model. These showed that the nature of the Lewis base influences the selectivity over the reaction pathway, with N Lewis bases favoring the deprotonation mechanism and P bases the hydride abstraction one. The lower barrier of activation for 1-aza-9-boratriptycene and the higher products stability are due to a better interaction energy than its counterparts, itself due to electrostatic interactions with the methane moiety, favorable orbital overlaps allowed by the side-attack, and space proximity between the B and N atoms. 相似文献
997.
Bowen Zhu Kexuan Wang Haili Gao Qinhua Wang Xiaofeng Pan Mizi Fan 《Chemphyschem》2021,22(16):1675-1683
The unique physical structure and abundant surface functional groups of MXene make the grafted organic molecules exhibit specific electrical and optical properties. This work reports the results of first-principles calculations to investigate the composite systems formed by different organic molecular monomers, namely acrylic acid (AA), acrylamide (AM), 1-aziridineethanol (1-AD) and glucose, and Ti3C2 MXene saturated with different functional groups, namely −OH, −O and −F. The results show that the interaction between organic molecules and the MXene surface depends on the type of functional groups of the organic molecules, while the strength of the interaction is determined by the type of surface functional groups and the number of hydrogen bonds. The bare Ti3C2 and Ti3C2(OH)2 can readily form strong chemical and hydrogen bonds with AA and AM molecules, leading to strong adsorption energy and a large amount of charge transfer, while the interaction between organic molecules and MXene saturated by −F or −O groups mainly exhibits physical interactions, accompanied by low adsorption energy and a small amount of charge transfer. This research provides theoretical guidance for the synthesis of high-performance MXene organic composite systems. 相似文献
998.
Recent studies have shown that dynamic nuclear polarization (DNP) can be used to detect 17O solid-state NMR spectra of naturally abundant samples within a reasonable experimental time. Observations using indirect DNP, which relies on 1H mediation in transferring electron hyperpolarization to 17O, are currently limited mostly to hydroxyls. Direct DNP schemes can hyperpolarize non-protonated oxygen near the radicals; however, they generally offer much lower signal enhancements. In this study, we demonstrate the detection of signals from non-protonated 17O in materials containing silicon. The sensitivity boost that made the experiment possible originates from three sources: indirect DNP excitation of 29Si via protons, indirect detection of 17O through 29Si nuclei using two-dimensional 29Si{17O} D-HMQC, and Carr-Purcell-Meiboom-Gill refocusing of 29Si magnetization during acquisition. This 29Si-detected scheme enabled, for the first time, 2D 17O−29Si heteronuclear correlation spectroscopy in mesoporous silica and silica-alumina surfaces at natural abundance. In contrast to the silanols showing motion-averaged 17O signals, the framework oxygens exhibit unperturbed powder patterns as unambiguous fingerprints of surface sites. Along with hydroxyl oxygens, detection of these moieties will help in gaining more atomistic-scale insights into surface chemistry. 相似文献
999.
Sílvia Quaresma Paula C. Alves Patrícia Rijo M. Teresa Duarte Vnia Andr 《Molecules (Basel, Switzerland)》2021,26(7)
The urge for the development of a more efficient antibiotic crystalline forms led us to the disclosure of new antibiotic coordination frameworks of pyrazinamide, a well-known drug used for the treatment of tuberculosis, with some of the novel compounds unravelling improved antimycobacterial activity. Mechanochemistry was the preferred synthetic technique to yield novel compounds, allowing the reproduction of a 1D zinc framework, the synthesis of a novel hydrogen bonding manganese framework, and three new compounds with silver. The structural characterization of the novel forms is presented along with stability studies. The increased antimicrobial activity of the new silver-based frameworks against Escherichia coli, Staphylococcus aureus, and Mycobacterium smegmatis is particularly relevant. 相似文献
1000.
Luk Petera Klaudia Mrazikova Lukas Nejdl Kristyna Zemankova Marketa Vaculovicova Adam Pastorek Svatopluk Civis Petr Kubelik Alan Heays Giuseppe Cassone Jiri Sponer Martin Ferus Judit Sponer 《Molecules (Basel, Switzerland)》2021,26(8)
Synthesis of RNA nucleobases from formamide is one of the recurring topics of prebiotic chemistry research. Earlier reports suggest that thymine, the substitute for uracil in DNA, may also be synthesized from formamide in the presence of catalysts enabling conversion of formamide to formaldehyde. In the current paper, we show that to a lesser extent conversion of uracil to thymine may occur even in the absence of catalysts. This is enabled by the presence of formic acid in the reaction mixture that forms as the hydrolysis product of formamide. Under the reaction conditions of our study, the disproportionation of formic acid may produce formaldehyde that hydroxymethylates uracil in the first step of the conversion process. The experiments are supplemented by quantum chemical modeling of the reaction pathway, supporting the plausibility of the mechanism suggested by Saladino and coworkers. 相似文献