Based on the building of a theoretical model for the large eddy structure, the nonlinear effect of the local rough wall on the large eddy structure in the boundary layer is studied by direct numerical simulation. Nume...Based on the building of a theoretical model for the large eddy structure, the nonlinear effect of the local rough wall on the large eddy structure in the boundary layer is studied by direct numerical simulation. Numerical results show that factors of the local rough feature, the distributing structure and the intensity, etc. play an important role in the evolution of the large eddy structure in the boundary layer.展开更多
Sum frequency generation vibrational spectroscopy(SFG-VS)is a powerful technique for determining molecular structures at both buried interface and air surface.Distinguishing the contribution of SFG signals from buried...Sum frequency generation vibrational spectroscopy(SFG-VS)is a powerful technique for determining molecular structures at both buried interface and air surface.Distinguishing the contribution of SFG signals from buried interface and air surface is crucial to the applications in devices such as microelectronics and bio-tips.Here we demonstrate that the SFG spectra from buried interface and air surface can be differentiated by controlling the film thickness and employment of surface-plasmon enhancement.Using substrate-supported PMMA(poly(methyl methacrylate))films as a model,we have visualized the variations in the contribution of SFG signals from buried interface and air surface.By monitoring carbonyl and C-H stretching groups,we found that SFG signals are dominated by the moieties(-CH2,-CH3,-OCH3 and C=O)segregated at the PMMA/air surface for the thin films while they are mainly contributed by the groups(-OCH3 and C=O)at the substrate/PMMA buried interface for the thick films.At the buried interface,the tilt angle of C=O decreases from65°to 43°as the film preparation concentration increases;in contrast,the angles at the air surface fall in the range from 38°to 21°.Surface plasmon generated by gold nanorods can largely enhance SFG signals,particularly the signals from the buried interface.展开更多
Alloyed nanoparticles with core-shell structures provide a favorable model to modulate interfacial interaction and surface structures at the atomic level,which is important for designing electrocatalysts with high act...Alloyed nanoparticles with core-shell structures provide a favorable model to modulate interfacial interaction and surface structures at the atomic level,which is important for designing electrocatalysts with high activity and durability.Herein,core-shell structured Pd3M@Pt/C nanoparticles with binary PdM alloy cores(M=Fe,Ni,and Co)and a monolayer Pt shell were successfully synthesized with diverse interfaces.Among these,Pd3Fe@Pt/C exhibited the best oxygen reduction reaction catalytic performance,roughly 5.4 times more than that of the commercial Pt/C catalyst used as reference.The significantly enhanced activity is attributed to the combined effects of strain engineering,interfacial electron transfer,and improved Pt utilization.Density functional theory simulations and extended X-ray absorption fine structure analysis revealed that engineering the alloy core with moderate lattice mismatch and alloy composition(Pd3Fe)optimizes the surface oxygen adsorption energy,thereby rendering excellent electrocatalytic activity.Future researches may use this study as a guide on the construction of highly effective core-shell electrocatalysts for various energy conversions and other applications.展开更多
Sum frequency generation vibrational spectroscopy(SFG-VS)has been demonstrated to be a powerful technique to study the interfacial structures and interactions of biomolecules at the molecular level.Yet most previous s...Sum frequency generation vibrational spectroscopy(SFG-VS)has been demonstrated to be a powerful technique to study the interfacial structures and interactions of biomolecules at the molecular level.Yet most previous studies mainly collected the SFG spectra in the frequency range of 1500–4000 cm-1,which is not always sufficient to describe the detailed interactions at surface and interface.Thorough knowledge of the complex biophysicochemical interactions between biomolecules and surface requires new ideas and advanced experimental methods for collecting SFG vibrational spectra.We introduced some advanced methods recently exploited by our group and others,including(1)detection of vibration modes in the fingerprint region;(2)combination of chiral and achiral polarization measurements;(3)SFG coupled with surface plasmon polaritons(SPPs);(4)imaging and microscopy approaches;and(5)ultrafast time-resolved SFG measurements.The technique that we integrated with these advanced methods may help to give a detailed and high-spatial-resolution 3D picture of interfacial biomolecules.展开更多
基金the National Natural Science Foundation of China(10672052)the Natural Science Foundation of Jiangsu Province(BK2007178)~~
文摘Based on the building of a theoretical model for the large eddy structure, the nonlinear effect of the local rough wall on the large eddy structure in the boundary layer is studied by direct numerical simulation. Numerical results show that factors of the local rough feature, the distributing structure and the intensity, etc. play an important role in the evolution of the large eddy structure in the boundary layer.
基金supported by the National Key Research and Development Program of China(No.2018YFA0208700 and No.2017YFA0303500)the National Natural Science Foundation of China(No.21925302,No.21633007,and No.21873090)Anhui Initiative in Quantum Information Technologies(AHY090000)。
文摘Sum frequency generation vibrational spectroscopy(SFG-VS)is a powerful technique for determining molecular structures at both buried interface and air surface.Distinguishing the contribution of SFG signals from buried interface and air surface is crucial to the applications in devices such as microelectronics and bio-tips.Here we demonstrate that the SFG spectra from buried interface and air surface can be differentiated by controlling the film thickness and employment of surface-plasmon enhancement.Using substrate-supported PMMA(poly(methyl methacrylate))films as a model,we have visualized the variations in the contribution of SFG signals from buried interface and air surface.By monitoring carbonyl and C-H stretching groups,we found that SFG signals are dominated by the moieties(-CH2,-CH3,-OCH3 and C=O)segregated at the PMMA/air surface for the thin films while they are mainly contributed by the groups(-OCH3 and C=O)at the substrate/PMMA buried interface for the thick films.At the buried interface,the tilt angle of C=O decreases from65°to 43°as the film preparation concentration increases;in contrast,the angles at the air surface fall in the range from 38°to 21°.Surface plasmon generated by gold nanorods can largely enhance SFG signals,particularly the signals from the buried interface.
基金the Natural Science Foundation of Hainan Province(2019RC007)the National Natural Science Foundation of China(21805104,21606050,21905056,21905045,and U1801257)+3 种基金the Natural Science Foundation of Guangdong Province(2018A0303130239,2018A0303130223)Pearl River Science and Technology New Star Project(201806010039)the Start-up Research Foundation of Hainan University(KYQD(ZR)1908)Research Fund Program of Key Laboratory of Fuel Cell Technology of Guangdong Province。
文摘Alloyed nanoparticles with core-shell structures provide a favorable model to modulate interfacial interaction and surface structures at the atomic level,which is important for designing electrocatalysts with high activity and durability.Herein,core-shell structured Pd3M@Pt/C nanoparticles with binary PdM alloy cores(M=Fe,Ni,and Co)and a monolayer Pt shell were successfully synthesized with diverse interfaces.Among these,Pd3Fe@Pt/C exhibited the best oxygen reduction reaction catalytic performance,roughly 5.4 times more than that of the commercial Pt/C catalyst used as reference.The significantly enhanced activity is attributed to the combined effects of strain engineering,interfacial electron transfer,and improved Pt utilization.Density functional theory simulations and extended X-ray absorption fine structure analysis revealed that engineering the alloy core with moderate lattice mismatch and alloy composition(Pd3Fe)optimizes the surface oxygen adsorption energy,thereby rendering excellent electrocatalytic activity.Future researches may use this study as a guide on the construction of highly effective core-shell electrocatalysts for various energy conversions and other applications.
基金supported by the National Basic Research Program of China(2010CB923300)the National Natural Science Foundation of China(21273217,91127042,21161160557)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘Sum frequency generation vibrational spectroscopy(SFG-VS)has been demonstrated to be a powerful technique to study the interfacial structures and interactions of biomolecules at the molecular level.Yet most previous studies mainly collected the SFG spectra in the frequency range of 1500–4000 cm-1,which is not always sufficient to describe the detailed interactions at surface and interface.Thorough knowledge of the complex biophysicochemical interactions between biomolecules and surface requires new ideas and advanced experimental methods for collecting SFG vibrational spectra.We introduced some advanced methods recently exploited by our group and others,including(1)detection of vibration modes in the fingerprint region;(2)combination of chiral and achiral polarization measurements;(3)SFG coupled with surface plasmon polaritons(SPPs);(4)imaging and microscopy approaches;and(5)ultrafast time-resolved SFG measurements.The technique that we integrated with these advanced methods may help to give a detailed and high-spatial-resolution 3D picture of interfacial biomolecules.
