The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-10^1 （Cr） were studied by gravimetric method and temperature-programmed desorpt...The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-10^1 （Cr） were studied by gravimetric method and temperature-programmed desorption （TPD） experiments. The MIL-101 crystals were synthesized by microwave irradiation method. The ad- sorption isotherms and kinetic curves of n-hexane on the MIL-101 were measured. Desorption activation energies of n-hexane from the MIL-10^1 were estimated by TPD experiments. The resulthowed that equilibrium amount ofn-hexane adsorbed on the MIL-10^1 was up to 5.62 mmol.g- 1 at 298 K and 1.6 x10^4 Pa, much higher than that of some activated carbons, zeolltes and so on. The isotherms of n-hexane on the MIL-101 could be well fitted with Langmuir-Freundlich model. TPD spectra exhibit two types of adsorption sites on the MIL-101 with desorption activation energies of 39.41 and 86.69 kJ. mol-1. It reflects the surface energy heterogeneity on the MIL-10I frameworks for n-hexane adsorption. The diffusion coefficients of n-hexane are in the range of （1.35- 2.35 ） x 10 - 1 o cm2. s - 1 with ad sorotion activation enerv of 16.33 kl. mol - 1.展开更多
Proteins adsorption at solid surfaces are of paramount important for many natural processes. However, the role of specific water in influencing the adsorption process has not been well understood. We used molecular dy...Proteins adsorption at solid surfaces are of paramount important for many natural processes. However, the role of specific water in influencing the adsorption process has not been well understood. We used molecular dynamics simulation to study the adsorption of BPTI on Au surface in three water environments （dielectric constant model, partial and full solvation models）. The result shows that a fast and strong adsorption can occur in the dielectric environment, which leads to significant structure changes, as confirmed by great deviation from the crystal structure, largely spreading along the Au surface, rapid lose in all secondary structures and the great number of atoms in contact with the surface. Compared to the dielectric model, slower adsorption and fewer changes in the calculated properties above are observed in the partial solvation system since the specific water layer weakens the adsorption effects. However, in the partial solvation system, the adsorption of polar Au surface causes a significant decrease in the specific hydration around the protein, which still results in large structure changes similar to the dielectric system, but with much less adsorption extent. Enough water molecules in the full solvation system could allow the protein to rotate, and to large extent preserve the protein native structure, thus leading to the slowest and weakest adsorption. On the whole, the effects of non-specific and specific solvation on the protein structure and adsorption dynamics are significantly different, highlighting the importance of the specific water molecule in the protein adsorption.展开更多
Heterostructures have lately been recognized as a viable implement to achieve high-energy Li-ion batteries(LIBs) because the as-formed built-in electric field can greatly accelerate the charge transfer kinetics. Herei...Heterostructures have lately been recognized as a viable implement to achieve high-energy Li-ion batteries(LIBs) because the as-formed built-in electric field can greatly accelerate the charge transfer kinetics. Herein, we have constructed the Mott-Schottky heterostructured VS2/MoS2 hybrids with tailorable 1T/2H phase based on their matchable formation energy, which are made of metallic and few-layered VS2 vertically grown on MoS2 surface. The density functional theory(DFT) calculations unveil that such heterojunctions drive the rearrangement of energy band with a facilitated reaction kinetics and enhance the Li adsorption energy more than twice compared to the MoS2 surface. Furthermore, the VS2 catalytically expedites the Li–S bond fracture and meantime the enriched Mo6+ enables the sulfur anchoring toward the oriented reaction with Li+to form Li2S, synergistically enhancing the reversibility of electrochemical redox. Consequently, the as-obtained VS2/MoS2 hybrids deliver a very large specific capacity of 1273 m Ah g^-1 at 0.1 A g^-1 with 61% retention even at 5 A g^-1. It can also stabilize 100 cycles at 0.5 A g^-1 and 500 cycles at 1 A g^-1. The findings provide in-depth insights into engineering heterojunctions towards the enhancement of reaction kinetics and reversibility for LIBs.展开更多
We propose a general multigroup model for cholera dynamics that involves both direct and indirect transmission pathways and that incorporates spatial heterogeneity. Under biologically feasible conditions, we show that...We propose a general multigroup model for cholera dynamics that involves both direct and indirect transmission pathways and that incorporates spatial heterogeneity. Under biologically feasible conditions, we show that the basic reproduction number R0 remains a sharp threshold for cholera dynamics in multigroup settings. We verify the analysis by numerical simulation results. We also perform an optimal control study to explore optimal vaccination strategy for cholera outbreaks.展开更多
基金Supported by the National Natural Science Foundation of China(21276092)the Research Foundation of State Key Lab of Subtropical Building Science of China(C713001z)+2 种基金the Science and Technology Research Foundation of Guangzhou City,China(200910814001)Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control(2011A060901011)the Fundamental Research Funds for the Central Universities(2013ZZ0060 and 2013ZM0056)
文摘The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-10^1 （Cr） were studied by gravimetric method and temperature-programmed desorption （TPD） experiments. The MIL-101 crystals were synthesized by microwave irradiation method. The ad- sorption isotherms and kinetic curves of n-hexane on the MIL-101 were measured. Desorption activation energies of n-hexane from the MIL-10^1 were estimated by TPD experiments. The resulthowed that equilibrium amount ofn-hexane adsorbed on the MIL-10^1 was up to 5.62 mmol.g- 1 at 298 K and 1.6 x10^4 Pa, much higher than that of some activated carbons, zeolltes and so on. The isotherms of n-hexane on the MIL-101 could be well fitted with Langmuir-Freundlich model. TPD spectra exhibit two types of adsorption sites on the MIL-101 with desorption activation energies of 39.41 and 86.69 kJ. mol-1. It reflects the surface energy heterogeneity on the MIL-10I frameworks for n-hexane adsorption. The diffusion coefficients of n-hexane are in the range of （1.35- 2.35 ） x 10 - 1 o cm2. s - 1 with ad sorotion activation enerv of 16.33 kl. mol - 1.
文摘Proteins adsorption at solid surfaces are of paramount important for many natural processes. However, the role of specific water in influencing the adsorption process has not been well understood. We used molecular dynamics simulation to study the adsorption of BPTI on Au surface in three water environments （dielectric constant model, partial and full solvation models）. The result shows that a fast and strong adsorption can occur in the dielectric environment, which leads to significant structure changes, as confirmed by great deviation from the crystal structure, largely spreading along the Au surface, rapid lose in all secondary structures and the great number of atoms in contact with the surface. Compared to the dielectric model, slower adsorption and fewer changes in the calculated properties above are observed in the partial solvation system since the specific water layer weakens the adsorption effects. However, in the partial solvation system, the adsorption of polar Au surface causes a significant decrease in the specific hydration around the protein, which still results in large structure changes similar to the dielectric system, but with much less adsorption extent. Enough water molecules in the full solvation system could allow the protein to rotate, and to large extent preserve the protein native structure, thus leading to the slowest and weakest adsorption. On the whole, the effects of non-specific and specific solvation on the protein structure and adsorption dynamics are significantly different, highlighting the importance of the specific water molecule in the protein adsorption.
基金This work was supported by the National Natural Science Foundation of China(51672082,21975074 and 91534202)the Basic Research Program of Shanghai(17JC1402300)+2 种基金the Shanghai Scientific and Technological Innovation Project(18JC1410500)the National Program for Support of Top-Notch Young Professionalsthe Fundamental Research Funds for the Central Universities(222201718002).
文摘Heterostructures have lately been recognized as a viable implement to achieve high-energy Li-ion batteries(LIBs) because the as-formed built-in electric field can greatly accelerate the charge transfer kinetics. Herein, we have constructed the Mott-Schottky heterostructured VS2/MoS2 hybrids with tailorable 1T/2H phase based on their matchable formation energy, which are made of metallic and few-layered VS2 vertically grown on MoS2 surface. The density functional theory(DFT) calculations unveil that such heterojunctions drive the rearrangement of energy band with a facilitated reaction kinetics and enhance the Li adsorption energy more than twice compared to the MoS2 surface. Furthermore, the VS2 catalytically expedites the Li–S bond fracture and meantime the enriched Mo6+ enables the sulfur anchoring toward the oriented reaction with Li+to form Li2S, synergistically enhancing the reversibility of electrochemical redox. Consequently, the as-obtained VS2/MoS2 hybrids deliver a very large specific capacity of 1273 m Ah g^-1 at 0.1 A g^-1 with 61% retention even at 5 A g^-1. It can also stabilize 100 cycles at 0.5 A g^-1 and 500 cycles at 1 A g^-1. The findings provide in-depth insights into engineering heterojunctions towards the enhancement of reaction kinetics and reversibility for LIBs.
文摘We propose a general multigroup model for cholera dynamics that involves both direct and indirect transmission pathways and that incorporates spatial heterogeneity. Under biologically feasible conditions, we show that the basic reproduction number R0 remains a sharp threshold for cholera dynamics in multigroup settings. We verify the analysis by numerical simulation results. We also perform an optimal control study to explore optimal vaccination strategy for cholera outbreaks.
