The effect of the degree of branching(DB) on glass transition temperature(T g) for a hyperbranced poly[3-ethyl-3-(hydroxymethyl)oxetane](PEHO) was measured by DSC. The results show that the T g of PEHO decreases with ...The effect of the degree of branching(DB) on glass transition temperature(T g) for a hyperbranced poly[3-ethyl-3-(hydroxymethyl)oxetane](PEHO) was measured by DSC. The results show that the T g of PEHO decreases with the increasing DB. It is presumed that the smaller the DB of the PEHO sample, the smaller the free volume of the material, and the stronger the intermolecular interaction, which means more energy is needed to make the PEHO chains move, finally it leads to the increase of T g.展开更多
The on-surface synthesis from predesigned organic precursors can yield graphene nanoribbons(GNRs)with atomically precise widths,edge terminations and dopants,which facilitate the tunning of their electronic structures...The on-surface synthesis from predesigned organic precursors can yield graphene nanoribbons(GNRs)with atomically precise widths,edge terminations and dopants,which facilitate the tunning of their electronic structures.Here,we report the synthesis of novel sulfur-doped cove-edged GNRs(S-CGNRs)on Au(111)from a specifically designed precursor containing thiophene rings.Scanning tunneling microscopy and non-contact atomic force microscopy measurements elucidate the formation of S-CGNRs through subsequent polymerization and cyclodehydrogenation,which further result in crosslinked branched structures.Scanning tunneling spectroscopy results reveal the conduction band minimum of the S-CGNR locates at 1.2 e V.First-principles calculations show that the S-CGNR possesses an energy bandgap of 1.17 e V,which is evidently smaller than that of an undoped cove-edged GNR(1.7 e V),suggesting effective tuning of the bandgap by introducing sulfur atoms.Further increasing the coverage of precursors close to a monolayer results in the formation of linear-shaped S-CGNRs.The fabrication of S-CGNRs provides one more candidate in the GNR toolbox and promotes the future applications of heteroatom-doped graphene nanostructures.展开更多
开发具有可控结构的过渡金属氧化物基电极材料对于高性能超级电容器尤为重要,但这仍是其目前面临的重要挑战之一.本文通过一种简单的软模板水热策略,首次合成了碗型Ni Co2O4纳米片团簇.这种碗型团簇由19 nm厚的超薄Ni Co2O4纳米片层构成...开发具有可控结构的过渡金属氧化物基电极材料对于高性能超级电容器尤为重要,但这仍是其目前面临的重要挑战之一.本文通过一种简单的软模板水热策略,首次合成了碗型Ni Co2O4纳米片团簇.这种碗型团簇由19 nm厚的超薄Ni Co2O4纳米片层构成,单个团簇平均直径为1μm,材料比表面积达到40 m2g^-1.在三电极测试中,作为电极材料的碗型Ni Co2O4纳米片团簇在1 A g^-1的电流密度下表现出高比电容值(1068 F g^-1),且循环5000次后仍有90%的电容保有率.此外,以该Ni Co2O4团簇和活性炭作为电极材料组装而成的不对称超级电容器在1 A g^-1的电流密度下展示出129 F g^-1的比电容;在0.66 k W kg^-1功率密度下,能量密度高达33 W h kg^-1.这些性能优于大部分商业化的超级电容器.本研究为构筑面向能量储存和转换应用的结构可控的新型有序过渡金属氧化物材料开辟了新途径.展开更多
文摘The effect of the degree of branching(DB) on glass transition temperature(T g) for a hyperbranced poly[3-ethyl-3-(hydroxymethyl)oxetane](PEHO) was measured by DSC. The results show that the T g of PEHO decreases with the increasing DB. It is presumed that the smaller the DB of the PEHO sample, the smaller the free volume of the material, and the stronger the intermolecular interaction, which means more energy is needed to make the PEHO chains move, finally it leads to the increase of T g.
基金the National Natural Science Foundation of China(Grant Nos.51761135130,61888102,and 21774076)the National Key Research and Development Program of China(Grant Nos.2018YFA0305800 and 2019YFA0308500)+3 种基金the DFG Enhance Nano(Grant No.391979941)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB30000000)the International Partnership Program of Chinese Academy of Sciences(Grant No.112111KYSB20160061)the K C Wong Education Foundation and the Program of Shanghai Academic Research Leader(Grant No.19XD1421700)。
文摘The on-surface synthesis from predesigned organic precursors can yield graphene nanoribbons(GNRs)with atomically precise widths,edge terminations and dopants,which facilitate the tunning of their electronic structures.Here,we report the synthesis of novel sulfur-doped cove-edged GNRs(S-CGNRs)on Au(111)from a specifically designed precursor containing thiophene rings.Scanning tunneling microscopy and non-contact atomic force microscopy measurements elucidate the formation of S-CGNRs through subsequent polymerization and cyclodehydrogenation,which further result in crosslinked branched structures.Scanning tunneling spectroscopy results reveal the conduction band minimum of the S-CGNR locates at 1.2 e V.First-principles calculations show that the S-CGNR possesses an energy bandgap of 1.17 e V,which is evidently smaller than that of an undoped cove-edged GNR(1.7 e V),suggesting effective tuning of the bandgap by introducing sulfur atoms.Further increasing the coverage of precursors close to a monolayer results in the formation of linear-shaped S-CGNRs.The fabrication of S-CGNRs provides one more candidate in the GNR toolbox and promotes the future applications of heteroatom-doped graphene nanostructures.
基金supported by the National Natural Science Foundation of China(21774076,61774102 and 51573091)the National Key Research and Development Program of China(2017YFE0195800)+2 种基金the Program of the Shanghai Committee of Science and Technology(17JC1403200)the Program of Shanghai Academic Research Leader(19XD1421700)the Program of Distinguished Professor of Special Appointment at Shanghai Institutions of Higher Learning。
文摘开发具有可控结构的过渡金属氧化物基电极材料对于高性能超级电容器尤为重要,但这仍是其目前面临的重要挑战之一.本文通过一种简单的软模板水热策略,首次合成了碗型Ni Co2O4纳米片团簇.这种碗型团簇由19 nm厚的超薄Ni Co2O4纳米片层构成,单个团簇平均直径为1μm,材料比表面积达到40 m2g^-1.在三电极测试中,作为电极材料的碗型Ni Co2O4纳米片团簇在1 A g^-1的电流密度下表现出高比电容值(1068 F g^-1),且循环5000次后仍有90%的电容保有率.此外,以该Ni Co2O4团簇和活性炭作为电极材料组装而成的不对称超级电容器在1 A g^-1的电流密度下展示出129 F g^-1的比电容;在0.66 k W kg^-1功率密度下,能量密度高达33 W h kg^-1.这些性能优于大部分商业化的超级电容器.本研究为构筑面向能量储存和转换应用的结构可控的新型有序过渡金属氧化物材料开辟了新途径.
