排序方式: 共有165条查询结果,搜索用时 15 毫秒
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Dr. Kavita Kumar Dr. Laetitia Dubau Dr. Michel Mermoux Dr. Jingkun Li Dr. Andrea Zitolo Dr. Jaysen Nelayah Dr. Frédéric Jaouen Dr. Frédéric Maillard 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3261-3269
Fe-N-C catalysts containing atomic FeNx sites are promising candidates as precious-metal-free catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. The durability of Fe-N-C catalysts in fuel cells has been extensively studied using accelerated stress tests (AST). Herein we reveal stronger degradation of the Fe-N-C structure and four-times higher ORR activity loss when performing load cycling AST in O2- vs. Ar-saturated pH 1 electrolyte. Raman spectroscopy results show carbon corrosion after AST in O2, even when cycling at low potentials, while no corrosion occurred after any load cycling AST in Ar. The load-cycling AST in O2 leads to loss of a significant fraction of FeNx sites, as shown by energy dispersive X-ray spectroscopy analyses, and to the formation of Fe oxides. The results support that the unexpected carbon corrosion occurring at such low potential in the presence of O2 is due to reactive oxygen species produced between H2O2 and Fe sites via Fenton reactions. 相似文献
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Si Li Liguang Xu Changlong Hao Maozhong Sun Xiaoling Wu Hua Kuang Chuanlai Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(52):19243-19248
In this study, we successfully synthesized CuxCoyS supraparticles (SPs) on the nanoscale featuring multiple pores inside and strong absorption from 400 to 900 nm. Porous CuxCoyS SPs produced the highest reactive oxygen species (ROS) yield (1.39) when illuminated with near‐infrared (NIR) light. Furthermore, we demonstrated that CuxCoyS SPs could be used to identify cancer cells through intracellular telomerase‐responsive fluorescence (FL) imaging in living cells. Because the CuxCoyS SPs were associated with telomerase‐responsive bioimaging and high ROS production, they can be efficiently used in the diagnosis and therapy of tumors with high selectivity and excellent therapeutic effects in vivo. This study provides a new vision for the creation of multifunctional SPs, which can be used as cellular sensors and control tools for pathologies across a broad range of biological systems. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(31):9172-9175
The rate coefficients for gas‐phase reaction of trifluoroacetic acid (TFA) with two Criegee intermediates, formaldehyde oxide and acetone oxide, decrease with increasing temperature in the range 240–340 K. The rate coefficients k(CH2OO + CF3COOH)=(3.4±0.3)×10−10 cm3 s−1 and k((CH3)2COO + CF3COOH)=(6.1±0.2)×10−10 cm3 s−1 at 294 K exceed estimates for collision‐limited values, suggesting rate enhancement by capture mechanisms because of the large permanent dipole moments of the two reactants. The observed temperature dependence is attributed to competitive stabilization of a pre‐reactive complex. Fits to a model incorporating this complex formation give k [cm3 s−1]=(3.8±2.6)×10−18 T2 exp((1620±180)/T) + 2.5×10−10 and k [cm3 s−1]=(4.9±4.1)×10−18 T2 exp((1620±230)/T) + 5.2×10−10 for the CH2OO + CF3COOH and (CH3)2COO + CF3COOH reactions, respectively. The consequences are explored for removal of TFA from the atmosphere by reaction with biogenic Criegee intermediates. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(11):3030-3034
Localized singlet diradicals are key intermediates in bond homolyses. The singlet diradicals are energetically much less stable than the σ‐bonded species. In general, only one‐way reactions from diradicals to σ‐bonded species are observed. In this study, a thermal equilibrium between a singlet 1,2‐diazacyclopentane‐3,5‐diyl diradical and the corresponding σ‐bonded species was directly observed. The singlet diradical was more stable than the σ‐bonded species. The solvent effect clarified key features, such as the zwitterionic character of the singlet diradical. The effect of the nitrogen atoms is discussed in detail. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(33):10042-10046
Heteroatom doping is an effective way to adjust the fluorescent properties of carbon quantum dots. However, selenium‐doped carbon dots have rarely been reported, even though selenium has unique chemical properties such as redox‐responsive properties owing to its special electronegativity. Herein, a facile and high‐output strategy to fabricate selenium‐doped carbon quantum dots (Se‐CQDs) with green fluorescence (quantum yield 7.6 %) is developed through the hydrothermal treatment of selenocystine under mild conditions. Selenium heteroatoms endow the Se‐CQDs with redox‐dependent reversible fluorescence. Furthermore, free radicals such as .OH can be effectively scavenged by the Se‐CQDs. Once Se‐CQDs are internalized into cells, harmful high levels of reactive oxygen species (ROS) in the cells are decreased. This property makes the Se‐CQDs capable of protecting biosystems from oxidative stress. 相似文献