Penta-graphene （PG）,a newly proposed two-dimensional material composed entirely of carbon pentagons,is believed to possess much lower failure stress and strain than those of graphene.An open question is whether and ...Penta-graphene （PG）,a newly proposed two-dimensional material composed entirely of carbon pentagons,is believed to possess much lower failure stress and strain than those of graphene.An open question is whether and how these properties can be enhanced.Herein using molecular dynamics simulations,we examine the deformation and failure processes of PG functionalized with different functional groups.We reveal that complete chemical functionalization leads to remarkable increases in the failure stress and strain of PG by up to 86.6% and 82.4%,respectively.The underlying reason for this enhancement is that the buckled pentagonal rings in pristine and partially functionalized PGs can easily transform into planar polygon rings under stretching;in contrast,complete functionalization of PG strongly stabilizes its structure and prevents such transformation,thereby significantly increasing the failure stress and strain.Our findings suggest a possible route to enhance the mechanical properties of PG for potential applications in nanocomposites and nanodevices.展开更多
As an emerging two-dimensional material,black phosphorus(BP)has fascinating structure and electronic properties,affording broad applications in fieldeffect transistors,optoelectronic devices,energy devices,and biomedi...As an emerging two-dimensional material,black phosphorus(BP)has fascinating structure and electronic properties,affording broad applications in fieldeffect transistors,optoelectronic devices,energy devices,and biomedicines.However,the lone pair electrons of phosphorus atoms readily react with oxygen,so few-layer BP is easily oxidized and degraded when exposed to air.Therefore,the ambient stability of BP needs to be enhanced for its potential application.Chemical functionalization is one of the most effective methods for improving the ambient stability of few-layer BP.In this review,we provide a comprehensive overview of the chemical functionalization of BP,focusing on covalent and noncovalent functionalization and surface coordination.The influence of the functionalization pattern on the electronic properties and ambient stability of BP is summarized.Finally,the challenges and future development of chemical functionalization of BP are discussed.展开更多
We propose a new type of quantum spin Hall （QSH） insulator in chemically functionalized As （110） and Sb （110） film. According to first-principles calculations, we find that metallic As （110） and Sb （110） fil...We propose a new type of quantum spin Hall （QSH） insulator in chemically functionalized As （110） and Sb （110） film. According to first-principles calculations, we find that metallic As （110） and Sb （110） films become QSH insulators after being chemically functionalized by hydrogen （H） or halogen （C1 and Br） atoms. The energy gaps of the functionalized films range from 0.121 eV to 0.304 eV, which are sufficiently large for practical applications at room temperature. The energy gaps originate from the spin-orbit coupling （SOC）. The energy gap increases linearly with the increase of the SOC strength λ/λ0. The Z2 invariant and the penetration depth of the edge states are also calculated and studied for the functionalized films.展开更多
Fifty-two samples of Miocene pelitic sedimentary rock from outcrops on Medvednica,Moslavacka Gora and Psunj Mts.,and boreholes in the Sava Depression and the Pozega Sub-depression were investigated.These sediments for...Fifty-two samples of Miocene pelitic sedimentary rock from outcrops on Medvednica,Moslavacka Gora and Psunj Mts.,and boreholes in the Sava Depression and the Pozega Sub-depression were investigated.These sediments formed in different marine（with normal and reduced salinity）,brackish,and freshwater environments,depending on the development stage of the Pannonian Basin System.Carbonate minerals,clay minerals and quartz are the main constituents of all pelitic sedimentary rocks,except in those from Moslavacka Gora Mt in which carbonate minerals are not present.Feldspars,pyrite,opal-CT,and hematite are present as minor constituents in some rocks.Besides calcite,dependent on the sedimentary environment and diagenetic changes,high-magnesium calcite,aragonite,dolomite and ankerite/Cadolomite are also present.Smectite or illite-smectite is the main clay minerals in the samples.Minor constituents,present in almost all samples,are detrital illite and kaolinite.In some samples chlorite is also present in a low amount.Major elements,trace elements and rare earth elements patterns used in provenance analysis show that all analysed samples have a composition similar to the values of the upper continental crust（UCC）.The contents of major and trace elements as well as SiO2/Al2O3,K2O/Al2O3,Na2O/K2O,Eu/Eu＊,La/Sc,Th/Sc,La/Co Th/Co,Th/Cr,Ce/Ce＊ and LREE/HREE ratios,show that the analysed pelitic sedimentary rocks were formed by weathering of different types of mostly acidic（silicic）,i.e.felsic rocks.展开更多
Cucumeropsis mannii, an underutilized oil seed was processed into raw full fat and defatted seed flours and its chemical, functional properties and anti-nutritional factors were determined using standard techniques. T...Cucumeropsis mannii, an underutilized oil seed was processed into raw full fat and defatted seed flours and its chemical, functional properties and anti-nutritional factors were determined using standard techniques. The effects of sample concentration and pH on the foaming properties of the seed flours were determined. The results showed that the full fat and defatted seed flours contained the following in g/100 g sample; 5.0 and 5.1; 45.8 and 1.0; 39.4 and 78.7; 3.45 and 4.40; 1.50 and 3.05; 4.85 and 7.75 for moisture, crude fat, protein, ash, crude fibre and carbohydrate, respectively. The most abundant mineral elements in the seed flour （mg/100 g） are potassium （198.5）, followed by nickel （30.0） and magnesium （28.4）. The water absorption capacity, oil absorption capacity, foaming capacity and stability, least gelation concentration, emulsion capacity and bulk density are 55.5% and 125.0%; 128.8% and 184.0%; 10.5% and 17.0%; 3.0% and 1.5%; 16.0% and 10.0 g/mL; 85.0 and 115.0 mL/g; 0.42 and 0.25 g/mL, respectively. Defatting influenced the functional properties. The foaming capacity is dependent on sample concentration and pH. The protein solubility of the full fat and defatted seed flours was minimum between pH 3 and 4 and maximum at pH 11. The anti-nutritional composition of the seed flour revealed the following： tannic acid, 1.54 mg/100 g; phytin phosphorus, 0.70 rag/g; phytic acid, 2.48 mg/g; oxalate, 1.85 mg/g; alkaloids 1.97% and saponin 0.50%. The seed flours （full fat and defatted） have potential as nutrient supplement, thickeners and emulsifiers in food system.展开更多
Both structure and interface engineering are highly effective strategies for enhancing the catalytic activity and selectivity of precious metal nanostructures.In this work,we develop a facile pyrolysis strategy to syn...Both structure and interface engineering are highly effective strategies for enhancing the catalytic activity and selectivity of precious metal nanostructures.In this work,we develop a facile pyrolysis strategy to synthesize the high-quality holey platinum nanotubes(Pt-H-NTs)using nanorods-like Pt^(Ⅱ)-phenanthroline(PT)coordination compound as self-template and self-reduction precursor.Then,an up-bottom strategy is used to further synthesize polyallylamine(PA)modified Pt-H-NTs(Pt-HNTs@PA).PA modification sharply promotes the catalytic activity of Pt-H-NTs for the formic acid electrooxidation reaction(FAEOR)by the direct reaction pathway.Meanwhile,PA modification also elevates the catalytic activity of Pt-H-NTs for the hydrogen evolution reaction(HER)by the proton enrichment at electrolyte/electrode interface.Benefiting from the high catalytic activity of Pt-H-NTs@PA for both FAEOR and HER,a two-electrode FAEOR boosted water electrolysis system is fabricated by using Pt-H-NTs@PA as bifunctio nal electrocatalysts.Such FAEOR boosted water electrolysis system only requires the operational voltage of 0.47 V to achieve the high-purity hydrogen production,showing an energy-saving hydrogen production strategy compared to traditional water electrolysis system.展开更多
Recently, the surface chemical functionalization and morphology control of precious metal nanostructures have been recognized as two efficient strategies for improving their electroactivity and/or selectivity. In this...Recently, the surface chemical functionalization and morphology control of precious metal nanostructures have been recognized as two efficient strategies for improving their electroactivity and/or selectivity. In this work, 1, 10-phenanthroline monohydrate(PM) functionalized Pt nanodendrites(Pt-NDs) on carbon cloth(CC)(denoted as PM@Pt-NDs/CC) and polyethylenimine(PEI) functionalized Pt-NDs on CC(denoted as PEI@Pt-NDs/CC) are successfully achieved by immersing Pt-NDs/CC into PM and PEI aqueous solutions, respectively. PEI functionalization of Pt-NDs/CC improves its electroactivity for hydrogen evolution reaction(HER) due to local proton enrichment whereas PM functionalization of Pt-NDs/CC improves its electroactivity for formic acid oxidation reaction(FAOR) by facilitating dehydrogenation pathway. With such high activity, a two-electrode electrolyzer is assembled using PM@Pt-NDs/CC as the anodic electrocatalyst and PEI@Pt-NDs/CC as the cathodic electrocatalyst for electrochemical reforming of formic acid, which only requires 0.45 V voltage to achieve the current density of 10 mA cm^(-1) for highpurity hydrogen production, much lower than conventional water electrolysis(1.59 V). The work presents an example of interfacial engineering enhancing electrocatalytic activity and indicates that electrochemical reforming of formic acid is an energy-saving electrochemical method for high-purity hydrogen production.展开更多
The thermodynamic properties of linear protein solutions are discussed by a statistical me-chanics theory with a lattice model. The numerical results show that the Gibbs function of the solution decreases, and the pro...The thermodynamic properties of linear protein solutions are discussed by a statistical me-chanics theory with a lattice model. The numerical results show that the Gibbs function of the solution decreases, and the protein chemical potential is enhanced with increase of the protein concentration for dilute solutions. The influences of chain length and temperature on the Gibbs function of the solution as well as the protein chemical potential are analyzed.As an application of the theory, the chemical potentials of some mutants of type I antifreeze proteins are computed and discussed.展开更多
The partial replacement of durum wheat semolina with local flours such as soybeans and yam reduces the dependence of durum wheat semolina for the production of pasta</span><span style="font-family:Verdan...The partial replacement of durum wheat semolina with local flours such as soybeans and yam reduces the dependence of durum wheat semolina for the production of pasta</span><span style="font-family:Verdana;">.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The</span><span style="font-family:""><span style="font-family:Verdana;"> main objective of this study is to develop yam flour (A) from Dioscorea alata in the manufacture of pasta made with durum wheat semolina (B) and soy flour (C) (raw materials). The methodology adopted consists first of all in the characterization of yam, soybean </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> durum wheat semolina. An experimental design was developed to bring out the balanced mixing plan in well-defined proportions with ten (10) tests. Chemical and functional analyzes were carried out on the pastes obtained from these formulations. The functional properties allowed us to determine the optimal mixing plan using a mathematical model. The sensory properties of the optimal compound dough were estimated in comparison with the control doughs. The results on the chemical properties of raw materials A, B </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> C obtained on the water content vary from 10.29% to 12.29%;those of ashes vary from 0.91% to 5.74% and those of proteins vary from 3.24% to 20.17%. The results of the chemical and functional parameters of compound pasta gave very diverse values. We find that the water content, the ash content, the protein content </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> the acidity rate of the series of 10 tests are respectively from 6.60% to 14.97%, from 0.97% to 1.67%, from 7.15% to 12.10% </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> from 1.35% to 3.60%. Regarding the optimal cooking time for this series of 10 tests, it varies from 15 min to 20 min with a swelling index which is between 59.70% and 107.12%. Statistical tests (test F) from the different models indicate that the main regression effects are not significant with a p-value probability greater than 0.05. The models obtained were significant with a good value for the coefficient of determination R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">. The sensory test approved that optimal compound pasta has good overall acceptability compared to 100% durum wheat pasta. The 20.40% yam flour mixture (102.020 g);55.19% of durum wheat semolina (275.982 g) and 24.39% of soy flour (121.998 g) has good potential in the preparation of compound pasta.展开更多
To elucidate the air pollution characteristics of northern China, airborne PM_10（atmospheric dynamic equivalent diameter ≤ 10 μm） and PM_（2.5）（atmospheric dynamic equivalent diameter ≤ 2.5 μm） were sampled i...To elucidate the air pollution characteristics of northern China, airborne PM_10（atmospheric dynamic equivalent diameter ≤ 10 μm） and PM_（2.5）（atmospheric dynamic equivalent diameter ≤ 2.5 μm） were sampled in three different functional areas（Yuzhong County,Xigu District and Chengguan District） of Lanzhou, and their chemical composition（elements, ions, carbonaceous species） was analyzed. The results demonstrated that the highest seasonal mean concentrations of PM_10（369.48 μg/m^3） and PM_（2.5）（295.42 μg/m^3） were detected in Xigu District in the winter, the lowest concentration of PM_（2.5）（53.15 μg/m^3） was observed in Yuzhong District in the fall and PM_10（89.60 μg/m^3） in Xigu District in the fall.The overall average OC/EC（organic carbon/elemental carbon） value was close to the representative OC/EC ratio for coal consumption, implying that the pollution of Lanzhou could be attributed to the burning of coal. The content of SNA（the sum of sulfate, nitrate,ammonium, SNA） in PM_（2.5）in Yuzhong County was generally lower than that at other sites in all seasons. The content of SNA in PM_（2.5）and PM_10 in Yuzhong County was generally lower than that at other sites in all seasons（0.24–0.38）, indicating that the conversion ratios from precursors to secondary aerosols in the low concentration area was slower than in the area with high and intense pollutants. Six primary particulate matter sources were chosen based on positive matrix factorization（PMF） analysis, and emissions from dust, secondary aerosols, and coal burning were identified to be the primary sources responsible for the particle pollution in Lanzhou.展开更多
Liver normal cells and cancer cells co-cultured on surfaces modified by different chemical functional groups, including mercapto （-SH）, hydroxyl （-OH） and methyl （-CHz） groups. The results showed that different ...Liver normal cells and cancer cells co-cultured on surfaces modified by different chemical functional groups, including mercapto （-SH）, hydroxyl （-OH） and methyl （-CHz） groups. The results showed that different cells exhibited changes in response to different surfaces. Normal cells on -SH surface exhibited the smallest contact area with mostly rounded morphology, which led to the death of cancer cells, while cancer cells could not grow on -CH3 groups, which also died. In the co-culture system, the -CH3 group exhibited its unique effect that could trigger the death of cancer cells and had no effects on normal cells. Our findings provide useful information on strategies for the design of efficient and safe regenerative medicine materials.展开更多
The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction （ORR） is extremely important for accelerating the commercial viability of direct methanol fuel cells （DMFCs...The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction （ORR） is extremely important for accelerating the commercial viability of direct methanol fuel cells （DMFCs）. In this work, we present an efficient and template-free route for facile synthesis of cyanide （CN^-）-functionalized PtNi hollow nanospheres （PtNi@CN HNSs） with a high alloying degree using a simple cyanogel reduction method at room temperature. The physical and electrocatalytic properties of the PtNi@CN HNSs were investigated by various physical and electrochemical techniques. The PtNi@CN HNSs exhibited significantly enhanced electrocatalytic activity, durability, and particular methanol tolerance for the ORR as compared to commercial Pt black, and thus they are promising cathode electrocatalysts for DMFCs.展开更多
Nanocellulose,a biopolymer,has received wide attention from researchers owing to its superior physicochemical properties,such as high mechanical strength,low density,biodegradability,and biocompatibility.Nanocellulose...Nanocellulose,a biopolymer,has received wide attention from researchers owing to its superior physicochemical properties,such as high mechanical strength,low density,biodegradability,and biocompatibility.Nanocellulose can be extracted from wide range of sources,including plants,bacteria,and algae.Depending on the extraction process and dimensions(diameter and length),they are categorized into three main types:cellulose nanocrystals(CNCs),cellulose nanofibrils(CNFs),and bacterial nanocellulose(BNC).CNCs are a highly crystalline and needle-like structure,whereas CNFs have both amorphous and crystalline regions in their network.BNC is the purest form of nanocellulose.The nanocellulose properties can be tuned by chemical functionalization,which increases its applicability in biomedical applications.This review highlights the fabrication of different surface-modified nanocellulose to deliver active molecules,such as drugs,proteins,and plasmids.Nanocellulose-mediated delivery of active molecules is profoundly affected by its topographical structure and the interaction between the loaded molecules and nanocellulose.The applications of nanocellulose and its composites in tissue engineering have been discussed.Finally,the review is concluded with further opportunities and challenges in nanocellulose-mediated delivery of active molecules.展开更多
As the rate-determining step in native chemical ligation reactions, the thiol–thioester exchange step is important in determining the efficiency of the ligations of peptides. In the present study, systematic theoreti...As the rate-determining step in native chemical ligation reactions, the thiol–thioester exchange step is important in determining the efficiency of the ligations of peptides. In the present study, systematic theoretical calculations were carried out on the relationships between the structure of different thioesters and the free energy barriers of the thiol–thioester exchange step. According to the calculation results, the thiol–thioester exchange step is disfavored by the steric hindrance around the carbonyl center, while the electronic effect（i.e. conjugation and hyper-conjugation effects） becomes important when the steric hindrance is insignificant.展开更多
基金The authors gratefully acknowledge the computational support provided by Intersect Australia Ltd and A＇STAR Computational Resource Centre of Singapore This work was partially supported by a grant from the Science and Engineering Research Council, A＇STAR, Singapore （152-70-00017）. H. J. G. acknowledges support from the National Science Foundation （No. CMMI-1634492）.
文摘Penta-graphene （PG）,a newly proposed two-dimensional material composed entirely of carbon pentagons,is believed to possess much lower failure stress and strain than those of graphene.An open question is whether and how these properties can be enhanced.Herein using molecular dynamics simulations,we examine the deformation and failure processes of PG functionalized with different functional groups.We reveal that complete chemical functionalization leads to remarkable increases in the failure stress and strain of PG by up to 86.6% and 82.4%,respectively.The underlying reason for this enhancement is that the buckled pentagonal rings in pristine and partially functionalized PGs can easily transform into planar polygon rings under stretching;in contrast,complete functionalization of PG strongly stabilizes its structure and prevents such transformation,thereby significantly increasing the failure stress and strain.Our findings suggest a possible route to enhance the mechanical properties of PG for potential applications in nanocomposites and nanodevices.
基金the National Key Research and Development Program of China(2017YFA0402800)the National Natural Science Foundation of China(51925206,U1932214).
文摘As an emerging two-dimensional material,black phosphorus(BP)has fascinating structure and electronic properties,affording broad applications in fieldeffect transistors,optoelectronic devices,energy devices,and biomedicines.However,the lone pair electrons of phosphorus atoms readily react with oxygen,so few-layer BP is easily oxidized and degraded when exposed to air.Therefore,the ambient stability of BP needs to be enhanced for its potential application.Chemical functionalization is one of the most effective methods for improving the ambient stability of few-layer BP.In this review,we provide a comprehensive overview of the chemical functionalization of BP,focusing on covalent and noncovalent functionalization and surface coordination.The influence of the functionalization pattern on the electronic properties and ambient stability of BP is summarized.Finally,the challenges and future development of chemical functionalization of BP are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474197,U1632272,and 11521404)
文摘We propose a new type of quantum spin Hall （QSH） insulator in chemically functionalized As （110） and Sb （110） film. According to first-principles calculations, we find that metallic As （110） and Sb （110） films become QSH insulators after being chemically functionalized by hydrogen （H） or halogen （C1 and Br） atoms. The energy gaps of the functionalized films range from 0.121 eV to 0.304 eV, which are sufficiently large for practical applications at room temperature. The energy gaps originate from the spin-orbit coupling （SOC）. The energy gap increases linearly with the increase of the SOC strength λ/λ0. The Z2 invariant and the penetration depth of the edge states are also calculated and studied for the functionalized films.
基金funded by the Ministry of Science,Education and Sports,Republic of Croatia,Projects:Basic Geological Map of the Republic of Croatia,1:50,000(181-1811096-1093)the Map of Mineral and Energy Resources of the Republic of Croatia(1811811096-1104)+1 种基金Metamorphic and Magmatic Events in the Panonnian Basin Basement and Dinarides(119-1191155-1156)Evolutionary Changes of the Dinarides from Subduction to Modern Adriatic Beaches(119-1191155-1159)
文摘Fifty-two samples of Miocene pelitic sedimentary rock from outcrops on Medvednica,Moslavacka Gora and Psunj Mts.,and boreholes in the Sava Depression and the Pozega Sub-depression were investigated.These sediments formed in different marine（with normal and reduced salinity）,brackish,and freshwater environments,depending on the development stage of the Pannonian Basin System.Carbonate minerals,clay minerals and quartz are the main constituents of all pelitic sedimentary rocks,except in those from Moslavacka Gora Mt in which carbonate minerals are not present.Feldspars,pyrite,opal-CT,and hematite are present as minor constituents in some rocks.Besides calcite,dependent on the sedimentary environment and diagenetic changes,high-magnesium calcite,aragonite,dolomite and ankerite/Cadolomite are also present.Smectite or illite-smectite is the main clay minerals in the samples.Minor constituents,present in almost all samples,are detrital illite and kaolinite.In some samples chlorite is also present in a low amount.Major elements,trace elements and rare earth elements patterns used in provenance analysis show that all analysed samples have a composition similar to the values of the upper continental crust（UCC）.The contents of major and trace elements as well as SiO2/Al2O3,K2O/Al2O3,Na2O/K2O,Eu/Eu＊,La/Sc,Th/Sc,La/Co Th/Co,Th/Cr,Ce/Ce＊ and LREE/HREE ratios,show that the analysed pelitic sedimentary rocks were formed by weathering of different types of mostly acidic（silicic）,i.e.felsic rocks.
文摘Cucumeropsis mannii, an underutilized oil seed was processed into raw full fat and defatted seed flours and its chemical, functional properties and anti-nutritional factors were determined using standard techniques. The effects of sample concentration and pH on the foaming properties of the seed flours were determined. The results showed that the full fat and defatted seed flours contained the following in g/100 g sample; 5.0 and 5.1; 45.8 and 1.0; 39.4 and 78.7; 3.45 and 4.40; 1.50 and 3.05; 4.85 and 7.75 for moisture, crude fat, protein, ash, crude fibre and carbohydrate, respectively. The most abundant mineral elements in the seed flour （mg/100 g） are potassium （198.5）, followed by nickel （30.0） and magnesium （28.4）. The water absorption capacity, oil absorption capacity, foaming capacity and stability, least gelation concentration, emulsion capacity and bulk density are 55.5% and 125.0%; 128.8% and 184.0%; 10.5% and 17.0%; 3.0% and 1.5%; 16.0% and 10.0 g/mL; 85.0 and 115.0 mL/g; 0.42 and 0.25 g/mL, respectively. Defatting influenced the functional properties. The foaming capacity is dependent on sample concentration and pH. The protein solubility of the full fat and defatted seed flours was minimum between pH 3 and 4 and maximum at pH 11. The anti-nutritional composition of the seed flour revealed the following： tannic acid, 1.54 mg/100 g; phytin phosphorus, 0.70 rag/g; phytic acid, 2.48 mg/g; oxalate, 1.85 mg/g; alkaloids 1.97% and saponin 0.50%. The seed flours （full fat and defatted） have potential as nutrient supplement, thickeners and emulsifiers in food system.
基金sponsored by the National Natural Science Foundation of China(22272103)the Natural Science Foundation of Shaanxi Province(2020JZ-23,2019KJXX-021,and 2020JM269)+7 种基金the Key Research and Development Program of Shaanxi(2020SF-355)the Science and Technology Innovation Team of Shaanxi Province(2022TD-35)the University Engineering Research Center of Crystal Growth and Applications of Guangdong Province(2020GCZX005)the Special Innovative Projects of Guangdong Province(2020KTSCX125)the Shenzhen Stable Supporting Program(SZWD2021015)the Fundamental Research Funds for the Central Universities(GK202202001)the Open Foundation of Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured Materials at Guangxi University(2021GXYSOF02)the 111 Project(B14041)。
文摘Both structure and interface engineering are highly effective strategies for enhancing the catalytic activity and selectivity of precious metal nanostructures.In this work,we develop a facile pyrolysis strategy to synthesize the high-quality holey platinum nanotubes(Pt-H-NTs)using nanorods-like Pt^(Ⅱ)-phenanthroline(PT)coordination compound as self-template and self-reduction precursor.Then,an up-bottom strategy is used to further synthesize polyallylamine(PA)modified Pt-H-NTs(Pt-HNTs@PA).PA modification sharply promotes the catalytic activity of Pt-H-NTs for the formic acid electrooxidation reaction(FAEOR)by the direct reaction pathway.Meanwhile,PA modification also elevates the catalytic activity of Pt-H-NTs for the hydrogen evolution reaction(HER)by the proton enrichment at electrolyte/electrode interface.Benefiting from the high catalytic activity of Pt-H-NTs@PA for both FAEOR and HER,a two-electrode FAEOR boosted water electrolysis system is fabricated by using Pt-H-NTs@PA as bifunctio nal electrocatalysts.Such FAEOR boosted water electrolysis system only requires the operational voltage of 0.47 V to achieve the high-purity hydrogen production,showing an energy-saving hydrogen production strategy compared to traditional water electrolysis system.
基金sponsored by Natural Science Foundation of Shaanxi Province (2020JZ-23)the Fundamental Research Funds for the Central Universities (GK201901002, GK201701007 and GK201902014)the 111 Project (B14041)。
文摘Recently, the surface chemical functionalization and morphology control of precious metal nanostructures have been recognized as two efficient strategies for improving their electroactivity and/or selectivity. In this work, 1, 10-phenanthroline monohydrate(PM) functionalized Pt nanodendrites(Pt-NDs) on carbon cloth(CC)(denoted as PM@Pt-NDs/CC) and polyethylenimine(PEI) functionalized Pt-NDs on CC(denoted as PEI@Pt-NDs/CC) are successfully achieved by immersing Pt-NDs/CC into PM and PEI aqueous solutions, respectively. PEI functionalization of Pt-NDs/CC improves its electroactivity for hydrogen evolution reaction(HER) due to local proton enrichment whereas PM functionalization of Pt-NDs/CC improves its electroactivity for formic acid oxidation reaction(FAOR) by facilitating dehydrogenation pathway. With such high activity, a two-electrode electrolyzer is assembled using PM@Pt-NDs/CC as the anodic electrocatalyst and PEI@Pt-NDs/CC as the cathodic electrocatalyst for electrochemical reforming of formic acid, which only requires 0.45 V voltage to achieve the current density of 10 mA cm^(-1) for highpurity hydrogen production, much lower than conventional water electrolysis(1.59 V). The work presents an example of interfacial engineering enhancing electrocatalytic activity and indicates that electrochemical reforming of formic acid is an energy-saving electrochemical method for high-purity hydrogen production.
基金This work was supported by the National Natural Science Foundation of China （No.10764003 and No.30560039）.
文摘The thermodynamic properties of linear protein solutions are discussed by a statistical me-chanics theory with a lattice model. The numerical results show that the Gibbs function of the solution decreases, and the protein chemical potential is enhanced with increase of the protein concentration for dilute solutions. The influences of chain length and temperature on the Gibbs function of the solution as well as the protein chemical potential are analyzed.As an application of the theory, the chemical potentials of some mutants of type I antifreeze proteins are computed and discussed.
文摘The partial replacement of durum wheat semolina with local flours such as soybeans and yam reduces the dependence of durum wheat semolina for the production of pasta</span><span style="font-family:Verdana;">.</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">The</span><span style="font-family:""><span style="font-family:Verdana;"> main objective of this study is to develop yam flour (A) from Dioscorea alata in the manufacture of pasta made with durum wheat semolina (B) and soy flour (C) (raw materials). The methodology adopted consists first of all in the characterization of yam, soybean </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> durum wheat semolina. An experimental design was developed to bring out the balanced mixing plan in well-defined proportions with ten (10) tests. Chemical and functional analyzes were carried out on the pastes obtained from these formulations. The functional properties allowed us to determine the optimal mixing plan using a mathematical model. The sensory properties of the optimal compound dough were estimated in comparison with the control doughs. The results on the chemical properties of raw materials A, B </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> C obtained on the water content vary from 10.29% to 12.29%;those of ashes vary from 0.91% to 5.74% and those of proteins vary from 3.24% to 20.17%. The results of the chemical and functional parameters of compound pasta gave very diverse values. We find that the water content, the ash content, the protein content </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> the acidity rate of the series of 10 tests are respectively from 6.60% to 14.97%, from 0.97% to 1.67%, from 7.15% to 12.10% </span><span style="font-family:Verdana;">and</span><span style="font-family:Verdana;"> from 1.35% to 3.60%. Regarding the optimal cooking time for this series of 10 tests, it varies from 15 min to 20 min with a swelling index which is between 59.70% and 107.12%. Statistical tests (test F) from the different models indicate that the main regression effects are not significant with a p-value probability greater than 0.05. The models obtained were significant with a good value for the coefficient of determination R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;">. The sensory test approved that optimal compound pasta has good overall acceptability compared to 100% durum wheat pasta. The 20.40% yam flour mixture (102.020 g);55.19% of durum wheat semolina (275.982 g) and 24.39% of soy flour (121.998 g) has good potential in the preparation of compound pasta.
基金supported by the Special Scientific Research Funds for Environment Protection Commonweal Section (Nos.201409003,201309011)the National Natural Science Foundation of China (No.41375132)+2 种基金the CAS Strategic Priority Research Program (No.XDB05030400)the National Basic Research Program of China (No.2014CB441203)the Beijing Municipal Science and Technology Plan (No.Z131100006113013)
文摘To elucidate the air pollution characteristics of northern China, airborne PM_10（atmospheric dynamic equivalent diameter ≤ 10 μm） and PM_（2.5）（atmospheric dynamic equivalent diameter ≤ 2.5 μm） were sampled in three different functional areas（Yuzhong County,Xigu District and Chengguan District） of Lanzhou, and their chemical composition（elements, ions, carbonaceous species） was analyzed. The results demonstrated that the highest seasonal mean concentrations of PM_10（369.48 μg/m^3） and PM_（2.5）（295.42 μg/m^3） were detected in Xigu District in the winter, the lowest concentration of PM_（2.5）（53.15 μg/m^3） was observed in Yuzhong District in the fall and PM_10（89.60 μg/m^3） in Xigu District in the fall.The overall average OC/EC（organic carbon/elemental carbon） value was close to the representative OC/EC ratio for coal consumption, implying that the pollution of Lanzhou could be attributed to the burning of coal. The content of SNA（the sum of sulfate, nitrate,ammonium, SNA） in PM_（2.5）in Yuzhong County was generally lower than that at other sites in all seasons. The content of SNA in PM_（2.5）and PM_10 in Yuzhong County was generally lower than that at other sites in all seasons（0.24–0.38）, indicating that the conversion ratios from precursors to secondary aerosols in the low concentration area was slower than in the area with high and intense pollutants. Six primary particulate matter sources were chosen based on positive matrix factorization（PMF） analysis, and emissions from dust, secondary aerosols, and coal burning were identified to be the primary sources responsible for the particle pollution in Lanzhou.
基金Acknowledgements This work was in part supported by the National Basic Research Program of China （Grant No. 2011 CB606205）, the National Natural Science Foundation of China （Grant No. 51272236）, and the Program for 521 Excellent Talents ofZhejiang Sci-Tech University.
文摘Liver normal cells and cancer cells co-cultured on surfaces modified by different chemical functional groups, including mercapto （-SH）, hydroxyl （-OH） and methyl （-CHz） groups. The results showed that different cells exhibited changes in response to different surfaces. Normal cells on -SH surface exhibited the smallest contact area with mostly rounded morphology, which led to the death of cancer cells, while cancer cells could not grow on -CH3 groups, which also died. In the co-culture system, the -CH3 group exhibited its unique effect that could trigger the death of cancer cells and had no effects on normal cells. Our findings provide useful information on strategies for the design of efficient and safe regenerative medicine materials.
基金This research was sponsored by National Natural Science Foundation of China （Nos. 21473111 and 21376122）, Natural Science Foundation of Shaanxi Province （No. 2015JM2043）, and Fundamental Research Funds for the Central Universities （No. GK201602002）.
文摘The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction （ORR） is extremely important for accelerating the commercial viability of direct methanol fuel cells （DMFCs）. In this work, we present an efficient and template-free route for facile synthesis of cyanide （CN^-）-functionalized PtNi hollow nanospheres （PtNi@CN HNSs） with a high alloying degree using a simple cyanogel reduction method at room temperature. The physical and electrocatalytic properties of the PtNi@CN HNSs were investigated by various physical and electrochemical techniques. The PtNi@CN HNSs exhibited significantly enhanced electrocatalytic activity, durability, and particular methanol tolerance for the ORR as compared to commercial Pt black, and thus they are promising cathode electrocatalysts for DMFCs.
基金This research was supported by the Basic Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2018R1A6A1A03025582)and the National Research Foundation of Korea(NRF-2019R1D1A3A03103828).
文摘Nanocellulose,a biopolymer,has received wide attention from researchers owing to its superior physicochemical properties,such as high mechanical strength,low density,biodegradability,and biocompatibility.Nanocellulose can be extracted from wide range of sources,including plants,bacteria,and algae.Depending on the extraction process and dimensions(diameter and length),they are categorized into three main types:cellulose nanocrystals(CNCs),cellulose nanofibrils(CNFs),and bacterial nanocellulose(BNC).CNCs are a highly crystalline and needle-like structure,whereas CNFs have both amorphous and crystalline regions in their network.BNC is the purest form of nanocellulose.The nanocellulose properties can be tuned by chemical functionalization,which increases its applicability in biomedical applications.This review highlights the fabrication of different surface-modified nanocellulose to deliver active molecules,such as drugs,proteins,and plasmids.Nanocellulose-mediated delivery of active molecules is profoundly affected by its topographical structure and the interaction between the loaded molecules and nanocellulose.The applications of nanocellulose and its composites in tissue engineering have been discussed.Finally,the review is concluded with further opportunities and challenges in nanocellulose-mediated delivery of active molecules.
基金NSFC (No. 21202006)FRFCU (No. FRF-TP14-015A2) for financial supports and Super-computer Center of Shanghai and Shenzhen for technical supports
文摘As the rate-determining step in native chemical ligation reactions, the thiol–thioester exchange step is important in determining the efficiency of the ligations of peptides. In the present study, systematic theoretical calculations were carried out on the relationships between the structure of different thioesters and the free energy barriers of the thiol–thioester exchange step. According to the calculation results, the thiol–thioester exchange step is disfavored by the steric hindrance around the carbonyl center, while the electronic effect（i.e. conjugation and hyper-conjugation effects） becomes important when the steric hindrance is insignificant.
