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951.
Guoqiang Hou Qi Wang Dr. Di Xu Haifeng Fan Kaidi Liu Yangyang Li Prof. Xiang-Kui Gu Prof. Mingyue Ding 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(19):e202402053
Direct synthesis of dimethyl carbonate (DMC) from CO2 plays an important role in carbon neutrality, but its efficiency is still far from the practical application, due to the limited understanding of the reaction mechanism and rational design of efficient catalyst. Herein, abundant electron-enriched lattice oxygen species were introduced into CeO2 catalyst by constructing the point defects and crystal-terminated phases in the crystal reconstruction process. Benefitting from the acid-base properties modulated by the electron-enriched lattice oxygen, the optimized CeO2 catalyst exhibited a much higher DMC yield of 22.2 mmol g-1 than the reported metal-oxide-based catalysts at the similar conditions. Mechanistic investigations illustrated that the electron-enriched lattice oxygen can provide abundant sites for CO2 adsorption and activation, and was advantageous of the formation of the weakly adsorbed active methoxy species. These were facilitating to the coupling of methoxy and CO2 for the key *CH3OCOO intermediate formation. More importantly, the weakened adsorption of *CH3OCOO on the electron-enriched lattice oxygen can switch the rate-determining-step (RDS) of DMC synthesis from *CH3OCOO formation to *CH3OCOO dissociation, and lower the corresponding activation barriers, thus giving rise to a high performance. This work provides insights into the underlying reaction mechanism for DMC synthesis from CO2 and methanol and the design of highly efficient catalysts. 相似文献
952.
953.
Dong Zhang;Shuyu Li;Shaosong Gao;Siyao Fu;Kexin Liu;Dan He;Huapeng Liu;Xiaotao Zhang;Wenping Hu; 《中国化学》2024,42(14):1563-1570
The organic cocrystal strategy has provided a convenient and efficient platform for preparing organic photothermal materials. However, the rapidly directional preparation of cocrystals with desirable photothermal properties remains challenging due to a lack of suitable design ideas. Here, two new photothermal cocrystals, MTC and MFC, based on acceptor molecules (TCNQ and F4TCNQ) with different electron-withdrawing capacities were quickly prepared by the coprecipitation method, aiming to explore the effect of charge transfer (CT) interaction on photothermal properties. Compared with MTC, the stronger intermolecular CT interaction in MFC facilitates extending the absorption range (from the NIR-I to the NIR-II region) and enhancing the non-radiative transition process. Under the 808 nm laser irradiation, the photothermal conversion efficiency (PCE) of MFC is 54.6%, whereas MTC displays a mere 36.8%. The MFC cocrystal was further combined with a flexible polymer substrate (HPDMS) to prepare a flexible wearable heater (HPDMS@MFC), which exhibits excellent NIR-II photothermal performance. This work points out a research direction for the rapid assembly of efficient photothermal cocrystals and additionally provides an extensive application prospect for organic photothermal cocrystals in the field of wearable devices. 相似文献
954.
Qian-Cheng Luo;Ke-Xin Yu;Peng-Bo Jin;Ye-Ye Liu;Yuan-Qi Zhai;Yan-Zhen Zheng; 《中国化学》2024,42(4):391-396
One dihydride-bridged dimeric Dy(III) guanidinate complex, formulated as [{(Me3Si)2NC(NiPr)2}2Dy(μ-H)]2 (1Dy), was successfully isolated and the introduction of hydride bridges significantly reduces the intramolecular Dy(III)···Dy(III) distance to only 3.688(1) Å. To investigate the effect of such a short Dy(III)···Dy(III) distance on magnetism, we also prepared its dibromide-bridged analogue [{(Me3Si)2NC(NiPr)2}2Dy(μ-Br)]2 (2Dy), which has a much longer Dy(III)···Dy(III) distance of 4.605(4) Å. Surprisingly, 2Dy demonstrates much larger effective energy barrier for magnetization reversal (Ueff) and higher blocking temperature (TB). The worse performance of 1Dy is attributed to the concerted effect of strong antiferromagnetic interactions between Dy(III) ions (Jtotal = –2.683 cm–1) and the unparallel arrangement of magnetic principle axes of the Dy(III) ions for 1Dy. 相似文献
955.
Xingli Li;Jianli Liu;Manwai Yuen; 《Mathematical Methods in the Applied Sciences》2024,47(7):6446-6456
In this paper, we consider the blowup mechanism of regular solutions to the spherically symmetry relativistic Euler-Poisson equations with repulsive force and damping. By means of a weighted function and the structured functional, we show the regular solution will blow up in finite time. 相似文献
956.
层叠Blumlein脉冲发生器具有灵活紧凑的优点,但由于开关隔离问题没有得到广泛运用。设计了一种集成隔离全固态层叠Blumlein脉冲发生器,利用4绕组共模电感为脉冲形成网络充电、驱动供电和高电压隔离的器件,解决了半导体开关应用于层叠Blumlein脉冲发生器的问题。首先介绍了隔离的原理,设计了包含共模电感和同步光触发隔离组件,以及基于IGBT开关阵列的Blumlein脉冲形成网络,分析了层叠Blumlein脉冲发生器的充放电过程;其次,对设计的Blumlein脉冲形成网络与层叠Blumlein脉冲发生器进行电路仿真;搭建了8级层叠Blumlein脉冲发生器,在匹配负载上实验得到电压30.0 kV、电流604 A、脉宽237 ns的方波脉冲。 相似文献
957.
根据关键设备在直线加速器隧道内的布局,控制网布设在隧道地面和墙面。跟踪仪是直线加速器控制网测量的主要仪器,跟踪仪的测角误差是影响设备精度的关键因素。根据隧道墙面和地面网点的布局以及跟踪仪测量方案,对跟踪仪所有测量状态下的水平角和垂直角进行分解;然后通过高精度三坐标测量仪和跟踪仪联动测试,对分解后的角度进行高精度求解,解算值用于修正跟踪仪的实测角度。结果表明,不管是哪种测量状态,跟踪仪实测角度值均大于解算值;地面网点垂直角和水平角的偏差与跟踪仪的标称精度基本相当;墙面点水平角超过15°时,测角误差随着角度的增加而增大,在隧道控制网测量时需要对墙面点水平角进行修正。 相似文献
958.
Ruming Jiang;Zhangshan Liu;Tao Yang;Dezhi Yang;Dongge Ma;Ben Zhong Tang;Zujin Zhao; 《Advanced Optical Materials》2024,12(9):2302034
Robust organic luminescent materials radiating deep-red/near-infrared (DR/NIR) light are highly desired in organic light-emitting diodes (OLEDs). However, most reported DR/NIR materials show only moderate electroluminescence (EL) efficiencies accompanied by rock-ribbed efficiency roll-offs, which immensely limit their practical use in OLEDs. In this work, two tailor-made NIR luminescent materials with thermally activated delayed fluorescence (TADF) property are developed based on rigid and strong electron-accepting core of 2,7-bis(4-cyanophenyl)dibenzo[a,c]phenazine-11,12-dicarbonitrile and electron donors of triphenylamine or N,N-di([1,1′-biphenyl]-4-yl)phenylamine. They exhibit high photoluminescence quantum yields, fast reverse intersystem crossing processes and large horizontal dipole ratios. Their nondoped OLEDs show NIR lights with maximum external quantum efficiencies (ηext,maxS) of 0.59% at 856 nm and 1.14% at 850 nm. And their doped OLEDs radiate DR to NIR lights (646–737 nm) and attain superb ηext,maxs of up to 30.3% at 646 nm with small efficiency roll-offs. The state-of-the-art EL performances of both NIR TADF materials demonstrate their high potential as emitters in OLEDs and the insights gained in this work will enlighten the further development of efficient NIR luminescent materials. 相似文献
959.
高斯噪声是闪光图像中的主要噪声,将在密度反演等后续处理中被放大,严重影响密度重建及客体边界提取结果,因此,消高斯噪声是闪光图像消噪研究的重点内容。针对闪光照相图像噪声及照相客体轴旋转对称的特点,研究了基于三维块匹配滤波（Block Matching and 3D Filtering,BM3D）的闪光照相图像消噪算法,针对闪光照相图像中难以获得更高质量相似块的缺陷,在不破坏噪声独立性的情况下,通过对含噪退化图像进行旋转与镜像操作,增加了提供相似块的图像来源。同时,通过引入图像块的灰度变换,降低了原有相似性要求中的灰度值要求,提高了形状相似的要求,增加了获得高质量相似块的能力。图像的消噪结果表明,由于相似块的质量得到保证,用于闪光图像消噪的改进BM3D方法取得了更好的消噪效果。 相似文献
960.
Zhihai Yang;Guo-Xi Yang;Simin Jiang;Mengke Li;Weidong Qiu;Xiaomei Peng;Chenyang Shen;Yiyang Gan;Kunkun Liu;Deli Li;Shi-Jian Su; 《Advanced Optical Materials》2024,12(9):2301711
Polycyclic aromatic hydrocarbon (PAH) compounds are prospective materials for highly efficient narrowband organic light-emitting diodes. Specifically, boron-nitrogen doped PAHs exhibit multiple resonance (MR) effect toward thermally activated delayed fluorescence (TADF) and narrow full width at half-maximum (FWHM). Currently, the molecular design strategy for bathochromic-shifted narrowband MR-TADF emitters is a hotspot and challenging puzzle. Herein, a carbonyl is fused in the boron-nitrogen doped PAH for constructing a boron/nitrogen/carbonyl MR-TADF emitter. Benefiting from the carbonyl, the developed emitter exhibits enhanced intramolecular charge transfer and decreased reorganization energy, which displays bathochromic-shifted narrowband emission pertinently. As a consequence, the proof-of-concept compound TCZBAO achieves an emission peak at 522 nm and narrow FWHM of 39 nm, while the carbonyl-free TCZBAC exhibits an emission peak at 502 nm and FWHM of 46 nm. Maximum external quantum efficiencies of 36.1 % and 32.4 % are realized for the devices based on TCZBAO and TCZBAC, respectively, indicating the guiding significance of the proposed design strategy for developing bathochromic-shifted narrowband MR-TADF emitters. 相似文献