| 2 | Novel 2D CaCl crystals with metallicity, room-temperature ferromagnetism, heterojunction, piezoelectricity-like property and monovalent calcium ions显示文摘Under ambient conditions,the only known valence state of calcium ions is+2,and the corresponding crystals with calcium ions are insulating and nonferromagnetic.Here,using cryo-electron microscopy,we report direct observation of two-dimensional(2D)CaCl crystals on reduced graphene oxide(rGO)membranes,in which the calcium ions are only monovalent(i.e.+1).Remarkably,metallic rather than insulating properties are displayed by those CaCl crystals.More interestingly,room-temperature ferromagnetism,graphene-CaCl heterojunction,coexistence of piezoelectricity-like property and metallicity,as well as the distinct hydrogen storage and release capability of the CaCl crystals in rGO membranes are experimentally demonstrated.We note that such CaCl crystals are obtained by simply incubating rGO membranes in salt solutions below the saturated concentration,under ambient conditions.Theoretical studies suggest that the formation of those abnormal crystals is attributed to the strong cation-πinteractions of the Ca cations with the aromatic rings in the graphene surfaces.The findings highlight the realistic potential applications of such abnormal CaCl material with unusual electronic properties in designing novel transistors and magnetic devices,hydrogen storage,catalyzers,high-performance conducting electrodes and sensors,with a size down to atomic scale. | Lei Zhang Guosheng Shi Bingquan Peng Pengfei Gao Liang Chen Ni Zhong Liuhua Mu Lijuan Zhang Peng Zhang Lu Gou Yimin Zhao Shanshan Liang Jie Jiang Zejun Zhang Hongtao Ren Xiaoling Lei Ruobing Yi Yinwei Qiu Yufeng Zhang Xing Liu Minghong Wu Long Yan Chungang Duan Shengli Zhang Haiping Fang | 2021 | National Science Review2021，8，7： | 0 |
| 3 | Detection of the Farthest Globular Cluster NGC 6715 and Two Other GCs in Gamma-Rays with Fermi-LAT显示文摘In this paper,~12 yr long-term Pass 8 data from Fermi Large Area Telescope for the 157 globular clusters are carefully re-analyzed.Besides the 31 globular clusters reported in the fourth Fermi Large Area Telescope catalog Data Release 2,NGC 1851 is identified as a gamma-ray emitter and the significant gamma-ray emissions from NGC 6715 and NGC 6723 are detected.Especially NGC 6715 is located at a distance of 26.8 kpc,so far it is the farthest globular cluster detected in gamma-rays.A detailed analysis for these three globular clusters has been performed,but their gamma-ray pulsation emissions or flux variabilities are not found.The numbers of millisecond pulsars(MSPs)in these globular clusters are estimated under the assumption that each MSP inside globular clusters emits a similar amount of gamma-rays.Some possible origins of gamma-ray emission from globular clusters,such as MSPs,pulsar binary systems and/or dark matter,are discussed. | Min Yuan Chongyang Ren Pengfei Zhang Zejun Jiang Li Zhang | 2022 | Research in Astronomy and Astrophysics2022，22，11： | 0 |
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