Silicon carbide (SiC) has been prepared by passing natural gas over (100) oriented hot Si substrate at different temperatures in the range 930~1000℃. Reaction times of 60 and 90 min are used.Depth profile, using Auge...Silicon carbide (SiC) has been prepared by passing natural gas over (100) oriented hot Si substrate at different temperatures in the range 930~1000℃. Reaction times of 60 and 90 min are used.Depth profile, using Auger Electron Spectroscopy, shows the formation of SiC under a thin coating of carbon for the samples prepared at 930 and 950℃. Annealing, at 1050℃ for 12 h,results in a more pronounced formation of SiC. It is found that at the temperature of 1000℃and reaction times of 60 and 90 min, a hard diamond-like coating is formed.展开更多
Nano-Scale mapping of minerals and organic compounds give unprecedented high resolution information on the origin and nature of substances,and provide new insight on their correlative distribution and interaction,thus...Nano-Scale mapping of minerals and organic compounds give unprecedented high resolution information on the origin and nature of substances,and provide new insight on their correlative distribution and interaction,thus present a powerful tool to study the progressive changes of geological samples,and may even be applied to study extraterrestrial samples in search of life.One example we present here explore the use of elemental microprobe,X-Ray Photon Spectroscopy(XPS),and synchrotron-based Scanning Transmission X-ray Microscopy(STXM) coupled with Near Edge X-ray Absorption Fine Structure(NEXAFS) Spectroscopy to investigate the surface properties and stability of micron-size organic carbonaceous particles from Central Amazon,Brazil,specifically focusing on black carbon in Kaolinitic Oxisol originated from anthropogenic processes,and their interaction with cations.展开更多
Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor int...Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.展开更多
A facile, economical and green strategy to prepare green-fluorescent nitrogen-doped carbon nanodots （N- CDs） with a quantum yield （QY） of approximately 31.91% has been built up, while aspartame was employed as the...A facile, economical and green strategy to prepare green-fluorescent nitrogen-doped carbon nanodots （N- CDs） with a quantum yield （QY） of approximately 31.91% has been built up, while aspartame was employed as the carbon-nitrogen source for the first time. The prepared N-CDs exhibited ultrahigh brightness, favorable strong photostability and negligible cytotoxicity. The outstanding optical properties are mainly derived from the their robost composition and steric distribution of the doped nitrogen atoms, which have been characterized detailedly. The obtained N-CDs showed highly selective and sensitive response toward ferric ions （Fe3＋） through a fluorescence static quenching process in a wide linear range of 0.005-60 μmol/L. The detection limit was as low as 1.43 nmol/L, allowing the analysis of Fe3＋ in a very simple method. The excitation-dependent luminescent behavior of the obtained N-CDs guaranteed the multicolor emissive property when they were used in cell imaging. And the application for intracellular Fe3＋ sensing further verified this novel N-CDs may open more opportunities in biosensor, bioimaging and biological assay.展开更多
Most studies do not consider the potential variation in carbon concentration among the different tree components of the same species in regional scale. This study examined the carbon concentrations of the compo- nents...Most studies do not consider the potential variation in carbon concentration among the different tree components of the same species in regional scale. This study examined the carbon concentrations of the compo- nents （i.e., foliage, branch, stem, and root） in a 10-year-old poplar species （Populus davidiana Dode） from the Desertification Combating Program of Northern China. The highest and lowest carbon concentrations were found in the stem and foliage, respectively. There was a significant difference in carbon concentrations among the different tree components. All of the observed carbon concentrations of tree components were lower than those predicted using the conversion factor of 0.5 applied to component biomass. Stem carbon made up 59.7% of the total tree biomass carbon. The power equation estimating proportion of tree biomass carbon against the independent variable of diameter at breast height explained more than 90% of the variability in allocation of carbon among tree components. Tree height, as a second independent variable is also discussed. Our results suggest that the difference in organic carbon concentration among tree components should be incorporated into accurately develop forest carbon budget. Moreover, further investigations on how the diameter at breast height equation developed in the present study performs across broader scales are required.展开更多
文摘Silicon carbide (SiC) has been prepared by passing natural gas over (100) oriented hot Si substrate at different temperatures in the range 930~1000℃. Reaction times of 60 and 90 min are used.Depth profile, using Auger Electron Spectroscopy, shows the formation of SiC under a thin coating of carbon for the samples prepared at 930 and 950℃. Annealing, at 1050℃ for 12 h,results in a more pronounced formation of SiC. It is found that at the temperature of 1000℃and reaction times of 60 and 90 min, a hard diamond-like coating is formed.
文摘Nano-Scale mapping of minerals and organic compounds give unprecedented high resolution information on the origin and nature of substances,and provide new insight on their correlative distribution and interaction,thus present a powerful tool to study the progressive changes of geological samples,and may even be applied to study extraterrestrial samples in search of life.One example we present here explore the use of elemental microprobe,X-Ray Photon Spectroscopy(XPS),and synchrotron-based Scanning Transmission X-ray Microscopy(STXM) coupled with Near Edge X-ray Absorption Fine Structure(NEXAFS) Spectroscopy to investigate the surface properties and stability of micron-size organic carbonaceous particles from Central Amazon,Brazil,specifically focusing on black carbon in Kaolinitic Oxisol originated from anthropogenic processes,and their interaction with cations.
基金funded by the fellowship of the China Postdoctoral Science Foundation(No.2020M682134)the National Natural Science Foundation of China(Nos.41872149,42076220)the Shandong Postdoctoral Innovation Research Project。
文摘Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.
基金supported by the National Natural Science Foundation of China (21575022, 21535003) the National High Technology Research and Development Program of China (2015AA020502)+1 种基金 the Fundamental Research Funds for the Central Universities (2242016K41055)Qing Lan Project and the Priority Academic Program Development of Jiangsu Higher Education Institutions (1107047002)
文摘A facile, economical and green strategy to prepare green-fluorescent nitrogen-doped carbon nanodots （N- CDs） with a quantum yield （QY） of approximately 31.91% has been built up, while aspartame was employed as the carbon-nitrogen source for the first time. The prepared N-CDs exhibited ultrahigh brightness, favorable strong photostability and negligible cytotoxicity. The outstanding optical properties are mainly derived from the their robost composition and steric distribution of the doped nitrogen atoms, which have been characterized detailedly. The obtained N-CDs showed highly selective and sensitive response toward ferric ions （Fe3＋） through a fluorescence static quenching process in a wide linear range of 0.005-60 μmol/L. The detection limit was as low as 1.43 nmol/L, allowing the analysis of Fe3＋ in a very simple method. The excitation-dependent luminescent behavior of the obtained N-CDs guaranteed the multicolor emissive property when they were used in cell imaging. And the application for intracellular Fe3＋ sensing further verified this novel N-CDs may open more opportunities in biosensor, bioimaging and biological assay.
基金Acknowledgements We thank Xinqiang Zhang, Xinhua Zeng, and Xin Zhao for their assistance in the field survey and laboratory analysis. This work was funded jointly by the Strategic Priority Research Program of the Chinese Academy of Sciences （No. XDA05060600）, the Natural Science Foundation of Hebei Province （No. C2015503008）, and the Doctoral Initial Fund Project of Hebei Academy of Sciences （No. 20150503LR62-1）. We would also like to thank Christine Verhille at the University of British Columbia for her assistance with the English language and grammatical editing of the manuscript.
文摘Most studies do not consider the potential variation in carbon concentration among the different tree components of the same species in regional scale. This study examined the carbon concentrations of the compo- nents （i.e., foliage, branch, stem, and root） in a 10-year-old poplar species （Populus davidiana Dode） from the Desertification Combating Program of Northern China. The highest and lowest carbon concentrations were found in the stem and foliage, respectively. There was a significant difference in carbon concentrations among the different tree components. All of the observed carbon concentrations of tree components were lower than those predicted using the conversion factor of 0.5 applied to component biomass. Stem carbon made up 59.7% of the total tree biomass carbon. The power equation estimating proportion of tree biomass carbon against the independent variable of diameter at breast height explained more than 90% of the variability in allocation of carbon among tree components. Tree height, as a second independent variable is also discussed. Our results suggest that the difference in organic carbon concentration among tree components should be incorporated into accurately develop forest carbon budget. Moreover, further investigations on how the diameter at breast height equation developed in the present study performs across broader scales are required.
