The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,mo...The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme（SNG）. In contrast with routine N-doped graphene framework（NGF） with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^（-1）, a large surface area of 1531 m^2 g^（-1）, a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.展开更多
Objective Consuming phthalates may be due to the presence of food contact materials, such as plastic containers. In this study, we investigated the association between plastic container use and phthalate exposure in 2...Objective Consuming phthalates may be due to the presence of food contact materials, such as plastic containers. In this study, we investigated the association between plastic container use and phthalate exposure in 2,140 Shanghai adults. Methods Participants completed a questionnaire on the frequency of using plastic containers in different scenarios in the previous year （e.g., daily, weekly） and on the consumption of plastic-packaged foods in the previous three days （yes or no）. Urinary phthalate metabolites were used to assess the association between phthalate exposure and the use of plastic containers. Results The metabolites of di-（2-ethylhexyl） phthalate （DEHP） were the most frequently detected in urine. The results revealed that phthalate exposure was associated with consumption of plastic-packaged breakfast or processed food items in the previous three days. The consumption of these two food items had strong synergistic effects on increasing urinary concentrations of most phthalate metabolites. Conclusion Our results of plastic-packaged breakfast and processed food may be explained by the use of flexible plastic containers, indicating the importance of risk assessment for the application of flexible plastic containers.展开更多
基金supported by the National Key Research and Development Program(2016YFA0202500 and 2016YFA0200102)the Natural Scientific Foundation of China(21776019)
文摘The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme（SNG）. In contrast with routine N-doped graphene framework（NGF） with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^（-1）, a large surface area of 1531 m^2 g^（-1）, a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.
基金supported by the National Key Research and Development Program of China(No.2016YFD0400602)
文摘Objective Consuming phthalates may be due to the presence of food contact materials, such as plastic containers. In this study, we investigated the association between plastic container use and phthalate exposure in 2,140 Shanghai adults. Methods Participants completed a questionnaire on the frequency of using plastic containers in different scenarios in the previous year （e.g., daily, weekly） and on the consumption of plastic-packaged foods in the previous three days （yes or no）. Urinary phthalate metabolites were used to assess the association between phthalate exposure and the use of plastic containers. Results The metabolites of di-（2-ethylhexyl） phthalate （DEHP） were the most frequently detected in urine. The results revealed that phthalate exposure was associated with consumption of plastic-packaged breakfast or processed food items in the previous three days. The consumption of these two food items had strong synergistic effects on increasing urinary concentrations of most phthalate metabolites. Conclusion Our results of plastic-packaged breakfast and processed food may be explained by the use of flexible plastic containers, indicating the importance of risk assessment for the application of flexible plastic containers.
