共查询到20条相似文献,搜索用时 31 毫秒
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Kasper S. Pedersen Giulia Lorusso Juan Jos Morales Thomas Weyhermüller Stergios Piligkos Saurabh Kumar Singh Dennis Larsen Magnus Schau‐Magnussen Gopalan Rajaraman Marco Evangelisti Jesper Bendix 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(9):2426-2429
The reaction of fac‐[MIIIF3(Me3tacn)]⋅x H2O with Gd(NO3)3⋅5H2O affords a series of fluoride‐bridged, trigonal bipyramidal {GdIII3MIII2} (M=Cr ( 1 ), Fe ( 2 ), Ga ( 3 )) complexes without signs of concomitant GdF3 formation, thereby demonstrating the applicability even of labile fluoride‐complexes as precursors for 3d–4f systems. Molecular geometry enforces weak exchange interactions, which is rationalized computationally. This, in conjunction with a lightweight ligand sphere, gives rise to large magnetic entropy changes of 38.3 J kg−1 K−1 ( 1 ) and 33.1 J kg−1 K−1 ( 2 ) for the field change 7 T→0 T. Interestingly, the entropy change, and the magnetocaloric effect, are smaller in 2 than in 1 despite the larger spin ground state of the former secured by intramolecular Fe–Gd ferromagnetic interactions. This observation underlines the necessity of controlling not only the ground state but also close‐lying excited states for successful design of molecular refrigerants. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(24):6848-6852
The efficiency of continuous wave dynamic nuclear polarization (DNP) experiments decreases at the high magnetic fields used in contemporary high‐resolution NMR applications. To recover the expected signal enhancements from DNP, we explored time domain experiments such as NOVEL which matches the electron Rabi frequency to the nuclear Larmor frequency to mediate polarization transfer. However, satisfying this matching condition at high frequencies is technically demanding. As an alternative we report here frequency‐swept integrated solid effect (FS‐ISE) experiments that allow low power sweeps of the exciting microwave frequencies to constructively integrate the negative and positive polarizations of the solid effect, thereby producing a polarization efficiency comparable to (±10 % difference) NOVEL. Finally, the microwave frequency modulation results in field profiles that exhibit new features that we coin the “stretched” solid effect. 相似文献
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Rapid and Large-Scale Production of Multi-Fluorescence Carbon Dots by a Magnetic Hyperthermia Method
Zhijie Zhu Rui Cheng Dr. Luting Ling Dr. Qing Li Prof. Su Chen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3123-3129
The intrinsic low yield of carbon dots (CDs) is a barrier that limits practical application. Now, a magnetic hyperthermia (MHT) method is used to synthesize fluorescent CDs on a large scale (up to 85 g) in one hour (yield ca. 60 %). The reaction process is intensified by MHT since the efficient heating system enhances the energy transfer. CDs with blue, green, and yellow luminescence are synthesized by using carbamide and citrate with three different cations (Zn2+, Na+, K+), respectively. The CDs exhibit bright fluorescence under UV light and show excellent monodispersity and solubility in water. The alternation of photoluminescence (PL) emissions of these CDs is probably due to the difference in particle sizes and surface state. A bar coating technique is used to construct large-area emissive polymer/CDs films. CDs can insert themselves into the polymer chains by hydrogen bonding and electrostatic interactions. Wound healing efficiency can be enhanced by the Zn-CDs/PCL nanofibrous scaffold. 相似文献
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