Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind ...Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content (9.58 wt%), high surface area (417 m^2/g), and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles (NPs). The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs (about 1.0 ± 0.5 nm) to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger (4.4 ± 1.7 nm) and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity (conversion 100%) and selectivity (〉99%) in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst (conversion 89% and selectivity 90%). This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.展开更多
The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is...The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co_3W_3C (M_6 C type). The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M_6C→M_12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W_2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.展开更多
Poly(3-hexylthiophene) (P3HT) has received much attention as a good candidate to replace inorganic semiconductors for flexible electronics due to its solution-processability. However, the low charge mobility of P3...Poly(3-hexylthiophene) (P3HT) has received much attention as a good candidate to replace inorganic semiconductors for flexible electronics due to its solution-processability. However, the low charge mobility of P3HT is an obstacle to its commercialization. To overcome this problem, we propose a new non-covalent functionalization method for carbon nanotubes (CNTs) for use in CNT/P3HT nanocomposites. By using modified pyrene molecules with hydrophobic long alkyl chains, the non-covalently functionalized CNTs can become well dispersed in hydrophobic solutions and organic semiconductor matrices. Fabrication of organic thin-film transistors (OTFTs) from the non-covalently functionalized CNT/organic semiconductor nanocomposites shows that our non-covalent functionalization method significantly reduces damage to CNTs during functionalization when compared with covalent functionalization by treatment with acids. The OTFTs show 15 times enhancement of field effect mobility (1.5 × 10^-2 cm^2/(V.s)) compared to the mobility of OTFTs made from pure P3HT. This enhancement is achieved by addition of only 0.25 wt% of CNTs to P3HT.展开更多
Rare earth doping has been widely applied in many functional nanomaterials with desirable properties and functions,which would have a significant effect on the growth process of the materials.However,the controlling s...Rare earth doping has been widely applied in many functional nanomaterials with desirable properties and functions,which would have a significant effect on the growth process of the materials.However,the controlling strategy is limited into high concentration of lanthanide doping,which produces concentration quenching of the lanthanide ion luminescence with an increase in the Ln^(3+)concentration,resulting in lowering the fluorescence quantum yield of lanthanide ion.Herein,for the first time,we demonstrate simultaneous control of the structures and luminescence properties of BaCO_3nanocrystals via a small amount of Tb^(3+)doping strategy.In fact,Tb^(3+)would partially occupy Ba^(2+)sites,resulting in the changes to the structures of the BaCO_3nanocrystals,which is primarily determined by charge modulation,including the contributions from the surfaces of crystal nuclei and building blocks.These structurally modified nanocrystals exhibit tunable luminescence properties,thus emerging as potential candidates for photonic devices such as light-emitting diodes and color displays.展开更多
基金supported by the National Natural Science Foundation of China(201573136,U1510105)the Scientific Research Start-up Funds of Shanxi University(RSC723)~~
文摘Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content (9.58 wt%), high surface area (417 m^2/g), and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles (NPs). The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs (about 1.0 ± 0.5 nm) to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger (4.4 ± 1.7 nm) and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity (conversion 100%) and selectivity (〉99%) in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst (conversion 89% and selectivity 90%). This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.
基金Projects(50323008, 50574104) supported by the National Natural Science Foundation of ChinaProject (04JJ3084) supported by the Natural Science Foundation of Hunan Province, China
文摘The phase composition, phase transition and phase structure transformation of the wire-cut section of functionally graded WC-Co cemented carbide with dual phase structure were investigated by XRD phase analysis. It is shown that the composition of η phase in the core zone is Co_3W_3C (M_6 C type). The structure of cobalt based solid solution binder phase is fcc type. At the cooling stage of the sintering process, the phase transition of η phase, i.e. M_6C→M_12C and the martensitic phase transition of the cobalt based solid solution binder phase, i.e. fcc→hcp are suppressed, which facilitates the strengthening of the alloy. Because the instantaneous temperature of the discharge channel is as high as 10 000 ℃ during the wire cutting process, the processed surface is oxidized. Nevertheless, the oxide layer thickness is in micro grade. In the oxide film, η phase is decomposed into W_2C and CoO, and cobalt based solid solution binder is selectively oxidized, while WC remains stable due to the existence of carbon containing liquid organic cutting medium.
文摘Poly(3-hexylthiophene) (P3HT) has received much attention as a good candidate to replace inorganic semiconductors for flexible electronics due to its solution-processability. However, the low charge mobility of P3HT is an obstacle to its commercialization. To overcome this problem, we propose a new non-covalent functionalization method for carbon nanotubes (CNTs) for use in CNT/P3HT nanocomposites. By using modified pyrene molecules with hydrophobic long alkyl chains, the non-covalently functionalized CNTs can become well dispersed in hydrophobic solutions and organic semiconductor matrices. Fabrication of organic thin-film transistors (OTFTs) from the non-covalently functionalized CNT/organic semiconductor nanocomposites shows that our non-covalent functionalization method significantly reduces damage to CNTs during functionalization when compared with covalent functionalization by treatment with acids. The OTFTs show 15 times enhancement of field effect mobility (1.5 × 10^-2 cm^2/(V.s)) compared to the mobility of OTFTs made from pure P3HT. This enhancement is achieved by addition of only 0.25 wt% of CNTs to P3HT.
基金supported by the National Natural Science Foundation of China (21403189, 21371149) Natural Science Foundation of Hebei Province (B2017203198)+1 种基金China Postdoctoral Science Foundation (2014M551047)Yanshan University Doctoral Foundation (B790)
文摘Rare earth doping has been widely applied in many functional nanomaterials with desirable properties and functions,which would have a significant effect on the growth process of the materials.However,the controlling strategy is limited into high concentration of lanthanide doping,which produces concentration quenching of the lanthanide ion luminescence with an increase in the Ln^(3+)concentration,resulting in lowering the fluorescence quantum yield of lanthanide ion.Herein,for the first time,we demonstrate simultaneous control of the structures and luminescence properties of BaCO_3nanocrystals via a small amount of Tb^(3+)doping strategy.In fact,Tb^(3+)would partially occupy Ba^(2+)sites,resulting in the changes to the structures of the BaCO_3nanocrystals,which is primarily determined by charge modulation,including the contributions from the surfaces of crystal nuclei and building blocks.These structurally modified nanocrystals exhibit tunable luminescence properties,thus emerging as potential candidates for photonic devices such as light-emitting diodes and color displays.