在分子氧-苯甲醛体系,由共沉淀法制备的Fe-Sn-O复合氧化物作为催化剂,催化分子氧化环己酮合成ε-己内酯,通过单因素实验,得到适宜的合成条件:常温常压下,以环己酮用量为5 mmol计;n(苯甲醛)∶n(环己酮)=3∶1;1,2-二氯乙烷20 m L;氧气流速...在分子氧-苯甲醛体系,由共沉淀法制备的Fe-Sn-O复合氧化物作为催化剂,催化分子氧化环己酮合成ε-己内酯,通过单因素实验,得到适宜的合成条件:常温常压下,以环己酮用量为5 mmol计;n(苯甲醛)∶n(环己酮)=3∶1;1,2-二氯乙烷20 m L;氧气流速20 m L/min;反应时间4 h;反应温度55°C.该条件下,ε-己内酯收率达到98.8%,选择性达到99.0%;采用SEM、XRD等对催化剂的结构进行表征;催化剂重复使用5次仍保持较高活性.展开更多
Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical phenomena.Recently,...Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical phenomena.Recently,FeS,the least studied Fe X compound(due to the difficulty in synthesizing high quality macroscopic crystals)attracted much attention because of its puzzling superconducting pairing symmetry.In this work,combining scanning tunneling microscopy and angle resolved photoemission spectroscopy(ARPES)with sub-micron spatial resolution,we investigate the intrinsic electronic structures of superconducting FeS from individual single crystalline domains.Unlike FeTe or FeSe,FeS remains identical tetragonal structure from room temperature down to 5 K,and the band structures observed can be well reproduced by our ab-initio calculations.Remarkably,mixed with the 1×1 tetragonal metallic phase,we also observe the coexistence of √5×√5 reconstructed insulating phase in the crystal,which not only helps explain the unusual properties of FeS,but also demonstrates the importance of using spatially resolved experimental tools in the study of this compound.展开更多
Electroluminescent characteristics of n-ZnO/p-GaN heterojunctions under forward and reverse biases are studied. Emissions at 389nm and 57Ohm are observed under forward bias. An unusual emission at 390ram appears under...Electroluminescent characteristics of n-ZnO/p-GaN heterojunctions under forward and reverse biases are studied. Emissions at 389nm and 57Ohm are observed under forward bias. An unusual emission at 390ram appears under reverse bias, and is attributed to the recombination in the p-GaN side of the heterojunction. The yellow emission peaked at 57Ohm is suppressed under reverse bias. The light intensity exponentially depends on the reverse current. The emission under reverse bias is correlated to tunnelling carrier transport in the heterostructure. Our results also support that the well-known yellow band of GaN comes from the transitions between some near-conduction-band-edge states and deep localized acceptor states.展开更多
文摘在分子氧-苯甲醛体系,由共沉淀法制备的Fe-Sn-O复合氧化物作为催化剂,催化分子氧化环己酮合成ε-己内酯,通过单因素实验,得到适宜的合成条件:常温常压下,以环己酮用量为5 mmol计;n(苯甲醛)∶n(环己酮)=3∶1;1,2-二氯乙烷20 m L;氧气流速20 m L/min;反应时间4 h;反应温度55°C.该条件下,ε-己内酯收率达到98.8%,选择性达到99.0%;采用SEM、XRD等对催化剂的结构进行表征;催化剂重复使用5次仍保持较高活性.
基金Project supported by CAS-Shanghai Science Research Center,China(Grant No.CAS-SSRC-YH-2015-01)the National Key R&D Program of China(Grant No.2017YFA0305400)+4 种基金the National Natural Science Foundation of China(Grant Nos.11674229,11227902,and 11604207)the EPSRC Platform Grant(Grant No.EP/M020517/1)Hefei Science Center,Chinese Academy of Sciences(Grant No.2015HSC-UE013)Science and Technology Commission of Shanghai Municipality,China(Grant No.14520722100)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB04040200)。
文摘Iron-based superconductor family FeX(X=S,Se,Te)has been one of the research foci in physics and material science due to their record-breaking superconducting temperature(FeSe film)and rich physical phenomena.Recently,FeS,the least studied Fe X compound(due to the difficulty in synthesizing high quality macroscopic crystals)attracted much attention because of its puzzling superconducting pairing symmetry.In this work,combining scanning tunneling microscopy and angle resolved photoemission spectroscopy(ARPES)with sub-micron spatial resolution,we investigate the intrinsic electronic structures of superconducting FeS from individual single crystalline domains.Unlike FeTe or FeSe,FeS remains identical tetragonal structure from room temperature down to 5 K,and the band structures observed can be well reproduced by our ab-initio calculations.Remarkably,mixed with the 1×1 tetragonal metallic phase,we also observe the coexistence of √5×√5 reconstructed insulating phase in the crystal,which not only helps explain the unusual properties of FeS,but also demonstrates the importance of using spatially resolved experimental tools in the study of this compound.
基金Supported by the National Natural Science Foundation under Grant Nos 60476044, 60376004 and 60021403, and the National Key Basic Research and Development Programme of China under Grant Nos 2002CB311903 and 2002CB613500.
文摘Electroluminescent characteristics of n-ZnO/p-GaN heterojunctions under forward and reverse biases are studied. Emissions at 389nm and 57Ohm are observed under forward bias. An unusual emission at 390ram appears under reverse bias, and is attributed to the recombination in the p-GaN side of the heterojunction. The yellow emission peaked at 57Ohm is suppressed under reverse bias. The light intensity exponentially depends on the reverse current. The emission under reverse bias is correlated to tunnelling carrier transport in the heterostructure. Our results also support that the well-known yellow band of GaN comes from the transitions between some near-conduction-band-edge states and deep localized acceptor states.
