With high water content,excellent biocompatibility and lubricating properties,and a microstructure similar to that of the extracellular matrix,hydrogel is becoming one of the most promising materials as a substitute f...With high water content,excellent biocompatibility and lubricating properties,and a microstructure similar to that of the extracellular matrix,hydrogel is becoming one of the most promising materials as a substitute for articular cartilage.However,it is a challenge for hydrogel materials to simultaneously satisfy high loading and low friction.Most hydrogels are brittle,with fracture energies of around 10 J·m^(-2),as compared with∼1000 J·m^(-2) for cartilage.A great deal of effort has been devoted to the synthesis of hydrogels with improved mechanical properties,such as increasing the compactness of the polymer network,introducing dynamic non-covalent bonds,and increasing the hydrophobicity of the polymer,all at the expense of the lubricating properties of the hydrogel.Herein,we develop a hydrogel material with anisotropic tubular structures where the compactness gradually decreases and eventually disappears from the surface to the subsurface,achieving a balance between lubrication and load-bearing.The porous layer with hydrophilic carboxyl groups on the surface exhibits extremely low friction(coefficient of friction(COF)∼0.003,1 N;COF∼0.08,20 N)against the hard steel ball,while the bottom layer acts as an excellent load-bearing function.What is more,the gradual transition of the tubular structures between the surface and the subsurface ensures the uniform distribution of friction stress between a lubricating and bearing layers,which endows the material with long-lasting and smooth friction properties.The extraordinary lubricious performance of the hydrogels with anisotropic tubular structure has potential applications in tissue engineering and medical devices.展开更多
A simple one-step thermal polymerization method was developed for synthesis of holey graphitic carbon nitride nanotubes,involving direci eating of mixtures of melamine and urea or melamine and cyanuric acid in specifi...A simple one-step thermal polymerization method was developed for synthesis of holey graphitic carbon nitride nanotubes,involving direci eating of mixtures of melamine and urea or melamine and cyanuric acid in specific mass ratios.Supramolecular structures formed betweer the precursor molecules guided nanotube formation.The porous and nanotubular structure of the nanotubes facilitated efficient charge carrier nigration and separation,thereby enhancing photocatalytic Hz production in 20 vol.%lactic acid under visible light irradiation.Nanotubes synthesized using melamine and urea in a 1:10 mass ratio(denoted herein as CN-MU nanotubes)exhibited a photocatalytic hydroger production rate of 1,073.6μmol·h^-1·^-g with Pt as the cocatalyst,a rate of 4.7 and 3.1 times higher than traditional Pt/g-CN4 photocatalysts prepared from graphitic carbon nitride(g-CN4)obtained by direct thermal polymerization of melamine or urea,respectively.On the basis of their outstanding performance for photocatalytic H2 production,it is envisaged that the holey g-C3N4 nanotubes will find widespread uptake in other areas,including photocatalytic CO2 reduction,dye-sensitized solar cells and photoelectrochemical sensors.展开更多
Maximizing atomic utilization of precious metalbased catalysts is of great significance in heterogeneous catalysis,also becoming a useful strategy to develop efficient electrocatalysts for hydrogen evolution reaction(...Maximizing atomic utilization of precious metalbased catalysts is of great significance in heterogeneous catalysis,also becoming a useful strategy to develop efficient electrocatalysts for hydrogen evolution reaction(HER).Although the dispersion of platinum(Pt)as single atoms(SAs)has increasingly been used in the design of HER electrocatalysts,it is still controversial if the SAs possess higher reactivity relative to the nanoparticles with identical atom loading.展开更多
Sinopec Jiujiang Petrochemical Company Ltd.started construction of900 000 t/a gasoline hydrogenation project on May 25th.The project is scheduled for startup in January 2010.Sinopec Jiujiang Petrochemical has capabili...Sinopec Jiujiang Petrochemical Company Ltd.started construction of900 000 t/a gasoline hydrogenation project on May 25th.The project is scheduled for startup in January 2010.Sinopec Jiujiang Petrochemical has capability of processing 6.5 milliontons of crude oil per year,and its refining facility produces Euro展开更多
SA508-Ⅲ steel was charged with different hydrogen(H) contents using a high-pressure thermal charging method to study the effects of H content on the tensile properties and evaluate the H embrittlement behavior of the...SA508-Ⅲ steel was charged with different hydrogen(H) contents using a high-pressure thermal charging method to study the effects of H content on the tensile properties and evaluate the H embrittlement behavior of the steel. The results indicate that the ultimate tensile strength remains nearly unchanged with the addition of H. In contrast, the yielding strength slightly increases, and the elongation significantly decreases with increasing H content, especially at concentrations exceeding 5.6 × 10-6. On the basis of fractographic analysis, it is clear that the addition of H changes the fracture mode from microvoid coalescence to a mixture of river patterns and dimples. Carbides are strong traps for H; thus, the H atoms easily migrate in the form of Cottrell atmosphere toward the carbides following moving dislocations during tensile deformation. In addition, stress-induced H atoms accumulate at the interface between carbides and the matrix after necking under three-dimensional stress, which weakens the interfacial bonding force. Consequently, when the local H concentration reaches a critical value, microcracks occur at the interface, resulting in fracture.展开更多
In order to broaden the absorption range of graphitic carbon nitride,one of the common methods is to couple the well-known photosensitizer porphyrin with graphitic carbon nitride through van der Waals weak in teractio...In order to broaden the absorption range of graphitic carbon nitride,one of the common methods is to couple the well-known photosensitizer porphyrin with graphitic carbon nitride through van der Waals weak in teractions.To date,to combine porphyrin with graphitic carbon nitridethrough covalent in teractions has not been settled.In this work,through rational molecular design,we successfully in corporated porphyrininto the matrixes of graphitic carbon nitride by covale nt bonding via on expot thermal copolymerization.The resulta nt material not only can wide nthe absorption range but also possess the enlarged specific surface area and construction intramolecular heterojunctions which can contributeto improve electron-holes separation efficiency.The resultant photocatalyst exhibited enhanced H2 production rate(7.6 mmol·g^-1·h^-1)and withthe apparent quantum efficiency(AQE)of 13.3%at 450 nm.At the same time,this method opens a way to fabricate graphitic carb on nitridenano sheets via bottom-up strategy.展开更多
Cultured meat produced through in vitro cell culture technology is regarded as a technical revolution.In this study,three-dimensional(3D)bioprinting technology was used to mimic the growth environment in vivo and cons...Cultured meat produced through in vitro cell culture technology is regarded as a technical revolution.In this study,three-dimensional(3D)bioprinting technology was used to mimic the growth environment in vivo and construct a 3D culture system in vilro.Hydroge1 bioinks,namely,sodium alginate-gelatin and gelatin-methacrylate(GelMA)-silk fbroin,produced using two different curing processes were blended,and their rheological properties,mechanical properties,and biocompatibilities were compared.The 4%GelMA-20%silk fibroin hydroge1(GS2)demonstrated good performance and was hybridized with porcine skeleta1 muscle satellite cells for 3D printing to construct network structures of size 15 mm×15 mm and porosity 1000 um in 4-,6-,and 8-1ayer struchures.After 16 days of culture,4-and 6-1ayer grid structures formed compact muscle fbers organized by multinucleated myotubes.These results suggested that 3D bioprinting and GeIMA-silk fbroin hydrogels have great potential in fabricating porcine skeleta1 muscle tissue for use as cultured meat.展开更多
Solar hydrogen production by the photoelectrochemical method promises a means to store solar energy.While it is generally understood that the process is highly sensitive to the nature of the interface between the semi...Solar hydrogen production by the photoelectrochemical method promises a means to store solar energy.While it is generally understood that the process is highly sensitive to the nature of the interface between the semiconductor and the electrolyte,a detailed understanding of this interface is still missing.For instance,few prior studies have established a clear relationship between the interface energetics and the catalyst loading amount.Here we aim to study this relationship on a prototypical Si-based photoelectrochemical system.Two types of interfaces were examined,one with GaN nanowires as a protection layer and one without.It was found that when GaN was present,higher Pt loading (> 0.1 μg/cm2) led to not only better water reduction (and,hence,hydrogen evolution) kinetics but also more favorable interface energetics for greater photovoltages.In the absence of the protection layer,by stark contrast,increased Pt loading exhibited no measurable influence on the interface energetics,and the main difference was observed only in the hydrogen evolution kinetics.The study sheds new light on the importance of interface engineering for further improvement of photoelectrochemical systems,especially concerning the role of catalysts and protection layers.展开更多
基金This research was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB 0470000)the National Natural Science Foundation of China(22032006,22072169 and 22102201)+3 种基金the National Key Research and Development Program of China(2021YFA0716304)the Key Research Project of Shandong Provincial Natural Science Foundation(ZR2021ZD27)the Gansu Province Basic Research Innovation Group Project(22JR5RA093)the Special Research Assistant Project of the Chinese Academy of Sciences。
文摘With high water content,excellent biocompatibility and lubricating properties,and a microstructure similar to that of the extracellular matrix,hydrogel is becoming one of the most promising materials as a substitute for articular cartilage.However,it is a challenge for hydrogel materials to simultaneously satisfy high loading and low friction.Most hydrogels are brittle,with fracture energies of around 10 J·m^(-2),as compared with∼1000 J·m^(-2) for cartilage.A great deal of effort has been devoted to the synthesis of hydrogels with improved mechanical properties,such as increasing the compactness of the polymer network,introducing dynamic non-covalent bonds,and increasing the hydrophobicity of the polymer,all at the expense of the lubricating properties of the hydrogel.Herein,we develop a hydrogel material with anisotropic tubular structures where the compactness gradually decreases and eventually disappears from the surface to the subsurface,achieving a balance between lubrication and load-bearing.The porous layer with hydrophilic carboxyl groups on the surface exhibits extremely low friction(coefficient of friction(COF)∼0.003,1 N;COF∼0.08,20 N)against the hard steel ball,while the bottom layer acts as an excellent load-bearing function.What is more,the gradual transition of the tubular structures between the surface and the subsurface ensures the uniform distribution of friction stress between a lubricating and bearing layers,which endows the material with long-lasting and smooth friction properties.The extraordinary lubricious performance of the hydrogels with anisotropic tubular structure has potential applications in tissue engineering and medical devices.
基金The authors are grateful for the financial support from the National Key R&D Program of China(Nos.2018YFB1502002,2017YFA0206904,2017YFA0206900,and 2016YFB0600901)the National Natural Science Foundation of China(Nos.51825205,U1662U&51772305,51572270,21871279,and 21802154)+4 种基金the Beijing Natural Science Foundation(Nos.2191002,218207&and 2194089)the Beijing Municipal Science and Technology Project(No.Z181100005118007)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17000000)the Royal Society-Newton Advanced Fellowship(No.NA170422)the International Partnership Program of Chinese Academy of Sciences(No.GJHZ1819)and the K.C.Wong Education Foundation.G.I.N.W.acknowledges funding support from the Energy Education Trust of New Zealand and the University of Auckland Faculty Research Development Fund.
文摘A simple one-step thermal polymerization method was developed for synthesis of holey graphitic carbon nitride nanotubes,involving direci eating of mixtures of melamine and urea or melamine and cyanuric acid in specific mass ratios.Supramolecular structures formed betweer the precursor molecules guided nanotube formation.The porous and nanotubular structure of the nanotubes facilitated efficient charge carrier nigration and separation,thereby enhancing photocatalytic Hz production in 20 vol.%lactic acid under visible light irradiation.Nanotubes synthesized using melamine and urea in a 1:10 mass ratio(denoted herein as CN-MU nanotubes)exhibited a photocatalytic hydroger production rate of 1,073.6μmol·h^-1·^-g with Pt as the cocatalyst,a rate of 4.7 and 3.1 times higher than traditional Pt/g-CN4 photocatalysts prepared from graphitic carbon nitride(g-CN4)obtained by direct thermal polymerization of melamine or urea,respectively.On the basis of their outstanding performance for photocatalytic H2 production,it is envisaged that the holey g-C3N4 nanotubes will find widespread uptake in other areas,including photocatalytic CO2 reduction,dye-sensitized solar cells and photoelectrochemical sensors.
基金supported by the National Natural Science Foundation of China(nos.21838003,91834301,and 21978278)the Shanghai Scientific and Technological Innovation Project(nos.18JC1410500 and 19JC1410400)the Fundamental Research Funds for the Central Universities(no.222201718002).
文摘Maximizing atomic utilization of precious metalbased catalysts is of great significance in heterogeneous catalysis,also becoming a useful strategy to develop efficient electrocatalysts for hydrogen evolution reaction(HER).Although the dispersion of platinum(Pt)as single atoms(SAs)has increasingly been used in the design of HER electrocatalysts,it is still controversial if the SAs possess higher reactivity relative to the nanoparticles with identical atom loading.
文摘Sinopec Jiujiang Petrochemical Company Ltd.started construction of900 000 t/a gasoline hydrogenation project on May 25th.The project is scheduled for startup in January 2010.Sinopec Jiujiang Petrochemical has capability of processing 6.5 milliontons of crude oil per year,and its refining facility produces Euro
基金financially supported by the Major State Basic Research Development Program of China (No. 2011CB610506)the National Natural Science Foundation of China (Nos. 51371044 and 51171039)the Fundamental Research Fund for the Central Universities, China (No. N130410001)
文摘SA508-Ⅲ steel was charged with different hydrogen(H) contents using a high-pressure thermal charging method to study the effects of H content on the tensile properties and evaluate the H embrittlement behavior of the steel. The results indicate that the ultimate tensile strength remains nearly unchanged with the addition of H. In contrast, the yielding strength slightly increases, and the elongation significantly decreases with increasing H content, especially at concentrations exceeding 5.6 × 10-6. On the basis of fractographic analysis, it is clear that the addition of H changes the fracture mode from microvoid coalescence to a mixture of river patterns and dimples. Carbides are strong traps for H; thus, the H atoms easily migrate in the form of Cottrell atmosphere toward the carbides following moving dislocations during tensile deformation. In addition, stress-induced H atoms accumulate at the interface between carbides and the matrix after necking under three-dimensional stress, which weakens the interfacial bonding force. Consequently, when the local H concentration reaches a critical value, microcracks occur at the interface, resulting in fracture.
文摘In order to broaden the absorption range of graphitic carbon nitride,one of the common methods is to couple the well-known photosensitizer porphyrin with graphitic carbon nitride through van der Waals weak in teractions.To date,to combine porphyrin with graphitic carbon nitridethrough covalent in teractions has not been settled.In this work,through rational molecular design,we successfully in corporated porphyrininto the matrixes of graphitic carbon nitride by covale nt bonding via on expot thermal copolymerization.The resulta nt material not only can wide nthe absorption range but also possess the enlarged specific surface area and construction intramolecular heterojunctions which can contributeto improve electron-holes separation efficiency.The resultant photocatalyst exhibited enhanced H2 production rate(7.6 mmol·g^-1·h^-1)and withthe apparent quantum efficiency(AQE)of 13.3%at 450 nm.At the same time,this method opens a way to fabricate graphitic carb on nitridenano sheets via bottom-up strategy.
文摘Cultured meat produced through in vitro cell culture technology is regarded as a technical revolution.In this study,three-dimensional(3D)bioprinting technology was used to mimic the growth environment in vivo and construct a 3D culture system in vilro.Hydroge1 bioinks,namely,sodium alginate-gelatin and gelatin-methacrylate(GelMA)-silk fbroin,produced using two different curing processes were blended,and their rheological properties,mechanical properties,and biocompatibilities were compared.The 4%GelMA-20%silk fibroin hydroge1(GS2)demonstrated good performance and was hybridized with porcine skeleta1 muscle satellite cells for 3D printing to construct network structures of size 15 mm×15 mm and porosity 1000 um in 4-,6-,and 8-1ayer struchures.After 16 days of culture,4-and 6-1ayer grid structures formed compact muscle fbers organized by multinucleated myotubes.These results suggested that 3D bioprinting and GeIMA-silk fbroin hydrogels have great potential in fabricating porcine skeleta1 muscle tissue for use as cultured meat.
文摘Solar hydrogen production by the photoelectrochemical method promises a means to store solar energy.While it is generally understood that the process is highly sensitive to the nature of the interface between the semiconductor and the electrolyte,a detailed understanding of this interface is still missing.For instance,few prior studies have established a clear relationship between the interface energetics and the catalyst loading amount.Here we aim to study this relationship on a prototypical Si-based photoelectrochemical system.Two types of interfaces were examined,one with GaN nanowires as a protection layer and one without.It was found that when GaN was present,higher Pt loading (> 0.1 μg/cm2) led to not only better water reduction (and,hence,hydrogen evolution) kinetics but also more favorable interface energetics for greater photovoltages.In the absence of the protection layer,by stark contrast,increased Pt loading exhibited no measurable influence on the interface energetics,and the main difference was observed only in the hydrogen evolution kinetics.The study sheds new light on the importance of interface engineering for further improvement of photoelectrochemical systems,especially concerning the role of catalysts and protection layers.
