Recent advances in utilizing ^(17)O isotopic labeling methods for solid-state nuclear magnetic resonance(NMR)investigations of metal oxides for lithium-ion batteries have yielded extensive insights into their structur...Recent advances in utilizing ^(17)O isotopic labeling methods for solid-state nuclear magnetic resonance(NMR)investigations of metal oxides for lithium-ion batteries have yielded extensive insights into their structural and dynamic details.Herein,we commence with a brief introduction to recent research on lithium-ion battery oxide materials studied using ^(17)O solid-state NMR spectroscopy.Then we delve into a review of ^(17)O isotopic labeling methods for tagging oxygen sites in both the bulk and surfaces of metal oxides.At last,the unresolved problems and the future research directions for advancing the ^(17)O labeling technique are discussed.展开更多
The copolymerizations of methyl acrylate （MA） with different N- arylmethacrylamide （N-ArMA） were carried out in benzene solution by free radical initiation. The compositions of the copolymers were deter mined by;H...The copolymerizations of methyl acrylate （MA） with different N- arylmethacrylamide （N-ArMA） were carried out in benzene solution by free radical initiation. The compositions of the copolymers were deter mined by;H NMR method. The monomer reactivity ratios were calculated by the Fineman-Ross （F-R） method. The reactivity ratios and the activity of various N-ArMA with MA were investigated.展开更多
近年来,31P-NMR(nuclear magnetic resonance)已成为研究环境有机磷的有力武器,然而此方法在湿地学研究中的应用却很少,关于湿地沉积物样品制备方法的研究更缺乏。本研究通过改变提取剂组成、提取剂比例、离心条件、检测扫描时间等因素...近年来,31P-NMR(nuclear magnetic resonance)已成为研究环境有机磷的有力武器,然而此方法在湿地学研究中的应用却很少,关于湿地沉积物样品制备方法的研究更缺乏。本研究通过改变提取剂组成、提取剂比例、离心条件、检测扫描时间等因素设计实验,寻找最佳的湿地沉积物样品处理及检测方法,以期为31P-NMR技术在湿地沉积物样品有机磷研究中的应用提供科学依据。结果表明采用:1mol·L-1 HCl预提取,0.25mol·L-1 NaOH+0.05mol·L-1 EDTA主提取,沉积物与提取剂比例为1∶8的提取方法,可获得更好的提取效果。提取完成后,采用冷冻高速离心可更好地分离提取液、避免某些磷组分的水解。此外,NMR扫描分析时间设为14~16h(约扫描25 000次)可获得更完整的图谱。相较于传统的化学分析法,31P-NMR法的样品前处理相对简单、分析时破坏性小且组分分辨完全,该技术的运用,有望获得湿地磷循环,特别是对有机磷认知的新突破。展开更多
为研究双峰孔隙结构对非饱和土力学特性的影响,以广西南宁和桂林2种典型双峰孔隙结构黏土为研究对象,分析了其在不同饱和度情况下的抗剪强度特性;辅以滤纸法及核磁共振(nuclear magnetic resonance,NMR)技术探究了2种土体在双峰孔隙结...为研究双峰孔隙结构对非饱和土力学特性的影响,以广西南宁和桂林2种典型双峰孔隙结构黏土为研究对象,分析了其在不同饱和度情况下的抗剪强度特性;辅以滤纸法及核磁共振(nuclear magnetic resonance,NMR)技术探究了2种土体在双峰孔隙结构情况下孔隙水分布状态对强度的影响机理。结果表明:饱和状态下,2种土体试样的T2分布曲线为双峰结构,且土样持水特性整体上均呈现双峰土水特征曲线;2种土体的应力-位移关系变化规律相似,抗剪强度与饱和度密切相关;在饱和度为40%前后土样黏聚力变化趋势发生改变,而内摩擦角则是在饱和度为80%时达到最小值。展开更多
α-Hydroxy ketones are frequently involved in biologically important compounds and,therefore,the determination of the stereochemistry of these structural elements has attracted the attention in natural products chemis...α-Hydroxy ketones are frequently involved in biologically important compounds and,therefore,the determination of the stereochemistry of these structural elements has attracted the attention in natural products chemistry.In this paper a simpler Mosher′s method was developed from the modified Mosher′s method.It only need one configuration of MTPA to determine the absolute configurations of four α-hydroxy ketones with their（S）-and（R）-MTPA esters using（）1H NMR.The signals of protons on the same side with phenyl ring will be in the higher field than those of on the different side ones.Consequently according to the model the main configuration of compounds 1,2,3 and 4 were determined as S,R,R and S, respectively.展开更多
基金supported by National Key R&D Program of China(2021YFA1502803)the National Natural Science Foundation of China(NSFC)(21972066,91745202)+3 种基金NSFC-Royal Society Joint Program(21661130149)L.P.thanks the Royal Society and Newton Fund for a Royal Society-Newton Advanced Fellowshipsupported by the Research Funds for the Frontiers Science Centre for Critical Earth Material Cycling,Nanjing Universitya Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Recent advances in utilizing ^(17)O isotopic labeling methods for solid-state nuclear magnetic resonance(NMR)investigations of metal oxides for lithium-ion batteries have yielded extensive insights into their structural and dynamic details.Herein,we commence with a brief introduction to recent research on lithium-ion battery oxide materials studied using ^(17)O solid-state NMR spectroscopy.Then we delve into a review of ^(17)O isotopic labeling methods for tagging oxygen sites in both the bulk and surfaces of metal oxides.At last,the unresolved problems and the future research directions for advancing the ^(17)O labeling technique are discussed.
文摘The copolymerizations of methyl acrylate （MA） with different N- arylmethacrylamide （N-ArMA） were carried out in benzene solution by free radical initiation. The compositions of the copolymers were deter mined by;H NMR method. The monomer reactivity ratios were calculated by the Fineman-Ross （F-R） method. The reactivity ratios and the activity of various N-ArMA with MA were investigated.
文摘为研究双峰孔隙结构对非饱和土力学特性的影响,以广西南宁和桂林2种典型双峰孔隙结构黏土为研究对象,分析了其在不同饱和度情况下的抗剪强度特性;辅以滤纸法及核磁共振(nuclear magnetic resonance,NMR)技术探究了2种土体在双峰孔隙结构情况下孔隙水分布状态对强度的影响机理。结果表明:饱和状态下,2种土体试样的T2分布曲线为双峰结构,且土样持水特性整体上均呈现双峰土水特征曲线;2种土体的应力-位移关系变化规律相似,抗剪强度与饱和度密切相关;在饱和度为40%前后土样黏聚力变化趋势发生改变,而内摩擦角则是在饱和度为80%时达到最小值。
文摘α-Hydroxy ketones are frequently involved in biologically important compounds and,therefore,the determination of the stereochemistry of these structural elements has attracted the attention in natural products chemistry.In this paper a simpler Mosher′s method was developed from the modified Mosher′s method.It only need one configuration of MTPA to determine the absolute configurations of four α-hydroxy ketones with their（S）-and（R）-MTPA esters using（）1H NMR.The signals of protons on the same side with phenyl ring will be in the higher field than those of on the different side ones.Consequently according to the model the main configuration of compounds 1,2,3 and 4 were determined as S,R,R and S, respectively.
