Noble single‐atom catalysts have rapidly been attracting attention due to their unique catalytic properties and maximized utilization.Atomic layer deposition(ALD)is an emerging powerful technique for large‐scale syn...Noble single‐atom catalysts have rapidly been attracting attention due to their unique catalytic properties and maximized utilization.Atomic layer deposition(ALD)is an emerging powerful technique for large‐scale synthesis of stable single atom.In this review,we summarize recent developments of single atom synthesized by ALD as well as explore future research direction and trends.展开更多
The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayla...The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene （ca 15 Ma） to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.展开更多
The synthesis of two-dimensional （2D） layered materials with controllable thickness is of considerable interest for diverse applications. Here we report the first chemical vapor deposition growth of single- and few-...The synthesis of two-dimensional （2D） layered materials with controllable thickness is of considerable interest for diverse applications. Here we report the first chemical vapor deposition growth of single- and few-layer MoSe2 nanosheets. By using Se and MoO3 as the chemical vapor supply, we demonstrate that highly crystalline MoSe2 can be directly grown on the 300 nm SiO2/Si substrates to form optically distinguishable single- and multi-layer nanosheets, typically in triangular shaped domains with edge lengths around 30 btm, which can merge into continuous thin films upon further growth. Micro-Raman spectroscopy and imaging was used to probe the thickness-dependent vibrational properties. Photoluminescence spectroscopy demonstrates that MoSe2 monolayers exhibit strong near band edge emission at 1.55 eV, while bilayers or multi-layers exhibit much weaker emission, indicating of the transition to a direct band gap semiconductor as the thickness is reduced to a monolayer.展开更多
Sr2Bi4Ti5O18(SBTi) single layered and Sr2Bi4Ti5O18 /Pb(Zr0.53Ti0.47)O3(SBTi/PZT) bilayered thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed-laser deposition(PLD).The related structural characteriz...Sr2Bi4Ti5O18(SBTi) single layered and Sr2Bi4Ti5O18 /Pb(Zr0.53Ti0.47)O3(SBTi/PZT) bilayered thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed-laser deposition(PLD).The related structural characterizations and electrical properties have been comparatively investigated.X-ray diffraction reveals that both films have crystallized into perovskite phases and scanning electron microscopy shows the sharp interfaces.Both films show well-saturated ferroelectric hysteresis loops,however,compared with the single layered SBTi films,the SBTi/PZT bilayered films have significantly increased remnant polarization(Pr) and decreased coercive field(Ec),with the applied field of 260 kV/cm.The measured Pr and Ec of SBTi and SBTi/PZT films were 7.9 C/cm 2,88.1 kV/cm and 13.0 C/cm 2,51.2 kV/cm,respectively.In addition,both films showed good fatigue-free characteristics,the switchable polarization decreased by 9% and 11% of the initial values after 2.2 10 9 switching cycles for the SBTi single layered films and the SBTi/PZT bilayered films,respectively.Our results may provide some guidelines for further optimization of multilayered ferroelectric thin films.展开更多
An indium tin oxide(ITO)electrode coated with monolayer TiO2/[Ru(phen)2(dC18bpy)] 2+ (phen=1,10-phenanthroline, dC18bpy=4,4′-dioctadecyl-2,2′-bipyridyl)hybrid film(denoted as ITO/TiO2-Ru)has been prepared using the ...An indium tin oxide(ITO)electrode coated with monolayer TiO2/[Ru(phen)2(dC18bpy)] 2+ (phen=1,10-phenanthroline, dC18bpy=4,4′-dioctadecyl-2,2′-bipyridyl)hybrid film(denoted as ITO/TiO2-Ru)has been prepared using the modified Langmuir-Blodgett(LB)method,and the electrocatalytic oxidation of mononucleotide of guanosine 5′-monophosphate(GMP)on an ITO/TiO2-Ru electrode after Pd-photodeposition(denoted as ITO/TiO2-Ru/Pd)has been studied.Atomic force microscopy reveals that the single-layered hybrid film of TiO2 nanosheets/[Ru(phen)2(dC18bpy)] 2+is closely packed at a surface pressure of 25 mN m 1and has a thickness of(3.20±0.5)nm.X-ray photoelectron spectra show the formation of Pd nanoparticles on the surface of hybrid film with radii of 20–200 nm by the reduction of[Pd(NH3)4] 2+ under light irradiation.When it is applied to oxidize GMP,a larger catalytic oxidative current is achieved on the ITO/TiO2-Ru/Pd electrode at the external potential above 700 mV(vs.Ag|AgCl|KCl)in comparison with the naked ITO electrode and ITO/TiO2-Ru electrode.Such a result indicates that the Pd nanoparticles are able to hamper the combination of electron hole pairs and reduce the counterwork of insulating long alkyl chains of amphiphilic Ru(II)complexes,and thus develops the electron transfer efficiency and produces the enhanced redox current.展开更多
Jurassic rocks are abundantly developed in the source area of the Yangtze River,South Qinghai,with the greatest thickness of 6311 m,including five stratigraphic units:Qoimaco Formation,Buqu Formation,Xiali Formation,S...Jurassic rocks are abundantly developed in the source area of the Yangtze River,South Qinghai,with the greatest thickness of 6311 m,including five stratigraphic units:Qoimaco Formation,Buqu Formation,Xiali Formation,Suowa Formation,and Xueshan Formation.Based on sufficient fossils of bivalves,ammonites,and brachiopods,the major part of these formations is ascribed to the Middle Jurassic Bathonian to Callovian.No diagnostic fossils have been found from the Lower Qoimaco Formation or Upper Xueshan Formation,which could possibly contain in part Bajocian and Oxfordian taxa respectively.展开更多
基金supported by the Natural Science and Engineering Research Council of Canada (NSERC)the Canada Research Chair Program (CRC) and the University of Western Ontario (UWO)
文摘Noble single‐atom catalysts have rapidly been attracting attention due to their unique catalytic properties and maximized utilization.Atomic layer deposition(ALD)is an emerging powerful technique for large‐scale synthesis of stable single atom.In this review,we summarize recent developments of single atom synthesized by ALD as well as explore future research direction and trends.
文摘The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northemmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene （ca 15 Ma） to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.
文摘The synthesis of two-dimensional （2D） layered materials with controllable thickness is of considerable interest for diverse applications. Here we report the first chemical vapor deposition growth of single- and few-layer MoSe2 nanosheets. By using Se and MoO3 as the chemical vapor supply, we demonstrate that highly crystalline MoSe2 can be directly grown on the 300 nm SiO2/Si substrates to form optically distinguishable single- and multi-layer nanosheets, typically in triangular shaped domains with edge lengths around 30 btm, which can merge into continuous thin films upon further growth. Micro-Raman spectroscopy and imaging was used to probe the thickness-dependent vibrational properties. Photoluminescence spectroscopy demonstrates that MoSe2 monolayers exhibit strong near band edge emission at 1.55 eV, while bilayers or multi-layers exhibit much weaker emission, indicating of the transition to a direct band gap semiconductor as the thickness is reduced to a monolayer.
基金supported by the National Natural Science Foundation(Grant Nos. 50805076 and 51275237)the National Natural Science Key Corporation Foundations (Grant No. 61161120323)Science Research Foundation at NUAA (Grant No. NS2012014)
文摘Sr2Bi4Ti5O18(SBTi) single layered and Sr2Bi4Ti5O18 /Pb(Zr0.53Ti0.47)O3(SBTi/PZT) bilayered thin films have been prepared on Pt/TiO2/SiO2/Si substrates by pulsed-laser deposition(PLD).The related structural characterizations and electrical properties have been comparatively investigated.X-ray diffraction reveals that both films have crystallized into perovskite phases and scanning electron microscopy shows the sharp interfaces.Both films show well-saturated ferroelectric hysteresis loops,however,compared with the single layered SBTi films,the SBTi/PZT bilayered films have significantly increased remnant polarization(Pr) and decreased coercive field(Ec),with the applied field of 260 kV/cm.The measured Pr and Ec of SBTi and SBTi/PZT films were 7.9 C/cm 2,88.1 kV/cm and 13.0 C/cm 2,51.2 kV/cm,respectively.In addition,both films showed good fatigue-free characteristics,the switchable polarization decreased by 9% and 11% of the initial values after 2.2 10 9 switching cycles for the SBTi single layered films and the SBTi/PZT bilayered films,respectively.Our results may provide some guidelines for further optimization of multilayered ferroelectric thin films.
基金supported by the National Natural Science Foundation of China(21073133,20843007,20471043)Zhejiang Provincial Natural Science Foundation of China(Y5100283,Y4090248,Y4080177)Wenzhou University Foundation(2007L019)
文摘An indium tin oxide(ITO)electrode coated with monolayer TiO2/[Ru(phen)2(dC18bpy)] 2+ (phen=1,10-phenanthroline, dC18bpy=4,4′-dioctadecyl-2,2′-bipyridyl)hybrid film(denoted as ITO/TiO2-Ru)has been prepared using the modified Langmuir-Blodgett(LB)method,and the electrocatalytic oxidation of mononucleotide of guanosine 5′-monophosphate(GMP)on an ITO/TiO2-Ru electrode after Pd-photodeposition(denoted as ITO/TiO2-Ru/Pd)has been studied.Atomic force microscopy reveals that the single-layered hybrid film of TiO2 nanosheets/[Ru(phen)2(dC18bpy)] 2+is closely packed at a surface pressure of 25 mN m 1and has a thickness of(3.20±0.5)nm.X-ray photoelectron spectra show the formation of Pd nanoparticles on the surface of hybrid film with radii of 20–200 nm by the reduction of[Pd(NH3)4] 2+ under light irradiation.When it is applied to oxidize GMP,a larger catalytic oxidative current is achieved on the ITO/TiO2-Ru/Pd electrode at the external potential above 700 mV(vs.Ag|AgCl|KCl)in comparison with the naked ITO electrode and ITO/TiO2-Ru electrode.Such a result indicates that the Pd nanoparticles are able to hamper the combination of electron hole pairs and reduce the counterwork of insulating long alkyl chains of amphiphilic Ru(II)complexes,and thus develops the electron transfer efficiency and produces the enhanced redox current.
基金supported by National Natural Science Foundation of China(Grant Nos.40772022,40972006)State Key Laboratory of Palaeobiology and Stratigraphy(Nanjing Institute of Geology and Paleontology)Chinese Academy of Sciences(Grant No.10311)
文摘Jurassic rocks are abundantly developed in the source area of the Yangtze River,South Qinghai,with the greatest thickness of 6311 m,including five stratigraphic units:Qoimaco Formation,Buqu Formation,Xiali Formation,Suowa Formation,and Xueshan Formation.Based on sufficient fossils of bivalves,ammonites,and brachiopods,the major part of these formations is ascribed to the Middle Jurassic Bathonian to Callovian.No diagnostic fossils have been found from the Lower Qoimaco Formation or Upper Xueshan Formation,which could possibly contain in part Bajocian and Oxfordian taxa respectively.
