Planar Na ion micro-supercapacitors(NIMSCs) that offer both high energy density and power density are deemed to a promising class of miniaturized power sources for wearable and portable microelectron-ics. Nevertheless...Planar Na ion micro-supercapacitors(NIMSCs) that offer both high energy density and power density are deemed to a promising class of miniaturized power sources for wearable and portable microelectron-ics. Nevertheless, the development of NIMSCs are hugely impeded by the low capacity and sluggish Na ion kinetics in the negative electrode.Herein, we demonstrate a novel carbon-coated Nb_(2)O_5 microflower with a hierarchical structure composed of vertically intercrossed and porous nanosheets, boosting Na ion storage performance. The unique structural merits, including uniform carbon coating, ultrathin nanosheets and abun-dant pores, endow the Nb_(2)O_5 microflower with highly reversible Na ion storage capacity of 245 mAh g^(-1) at 0.25 C and excellent rate capability.Benefiting from high capacity and fast charging of Nb_(2)O_5 microflower, the planar NIMSCs consisted of Nb_(2)O_5 negative electrode and activated car-bon positive electrode deliver high areal energy density of 60.7 μWh cm^(-2),considerable voltage window of 3.5 V and extraordinary cyclability. Therefore, this work exploits a structural design strategy towards electrode materials for application in NIMSCs, holding great promise for flexible microelectronics.展开更多
A robust and green strategy for the selective upgrading of biomass-derived platform chemicals towards highly valuable products is important for the sustainable development.Herein,the efficient electrocatalytic oxidati...A robust and green strategy for the selective upgrading of biomass-derived platform chemicals towards highly valuable products is important for the sustainable development.Herein,the efficient electrocatalytic oxidation of biomass-derived furfuryl alcohol(FFA)into furoic acid(FurAc)catalyzed by the electrodeposited non-precious NiFe microflowers was successfully reached under the low temperature and ambient pressure.The 3D hierarchical NiFe microflowers assembled from ultrathin nanosheets were controllably synthesized by the electrodeposition method and uniformly grown on carbon fiber paper(CFP).Electrochemical analysis confirmed that NiFe nanosheets more preferred in the selective oxidation of FFA(FFAOR)than oxygen evolution reaction(OER).The linear sweep voltammetry(LSV)in FFAOR displayed a clear decrease towards lower potential,resulting in 30 mV reduction of overpotential at 20 mA cm^(-2) compared with that of OER.The optimal catalyst Ni_(1)Fe_(2) nanosheets exhibited the highest selectivity of FurAc(94.0%)and 81.4%conversion of FFA within 3 h.Besides,the influence of various reaction parameters on FFAOR was then explored in details.After that,the reaction pathway was investigated and rationally proposed.The outstanding performance for FFAOR can be ascribed to the unique structure of 3D flower-like NiFe nanosheets and oxygen vacancies,resulting in large exposure of active sites,faster electron transfer and enhanced adsorption of reactants.Our findings highlight a facile and convenient mean with a promising green future,which is promising for processing of various biomass-derived platform chemicals into value-added products.展开更多
By means of similar physical simulation, liquid metal filling flow pattern in the microscale during the centrifugal casting process was studied. It was found that, in microscale, the flow channel with the maximum cros...By means of similar physical simulation, liquid metal filling flow pattern in the microscale during the centrifugal casting process was studied. It was found that, in microscale, the flow channel with the maximum cross-sectional area was filled first, and the micro flow channels with 0.1 mm in diameter were filled when the rotational speed was increased to 964 r/min. The total fluid energy remained constant during the mould filling, and the changes of cross-sectional area only occurred in the microflow channels with 0.3 mm in diameter. Filling velocity increased with processing time, and a peak value was achieved rapidly, followed by a gentle increase as the process proceeded further. The time required to achieve the peak filling rate decreased dramatically with increase of rotational speed.展开更多
Graphene has shown great potential in microwave absorption(MA) owing to its high surface area, low density,tunable electrical conductivity and good chemical stability.To fully realize graphenes& MA ability, the mi...Graphene has shown great potential in microwave absorption(MA) owing to its high surface area, low density,tunable electrical conductivity and good chemical stability.To fully realize graphenes& MA ability, the microstructure of graphene should be carefully addressed. Here we prepared graphene microflowers(Gmfs) with highly porous structure for high-performance MA filler material. The efficient absorption bandwidth(reflection loss B-10 dB) reaches 5.59 GHz and the minimum reflection loss is up to -42.9 dB, showing significant increment compared with stacked graphene. Such performance is higher than most graphene-based materials in the literature. Besides, the low filling content(10 wt%) and low density(40–50 mg cm^(-3))are beneficial for the practical applications. Without compounding with magnetic materials or conductive polymers,Gmfs show outstanding MA performance with the aid of rational microstructure design. Furthermore, Gmfs exhibit advantages in facile processibility and large-scale production compared with other porous graphene materials including aerogels and foams.展开更多
This paper presents the experimental results of liquid-liquid microflows in a coaxial microfluidic device with mass transfer.Three working systems were n-butanol + phosphoric acid(PA) + water,methyl isobutyl ketone(MI...This paper presents the experimental results of liquid-liquid microflows in a coaxial microfluidic device with mass transfer.Three working systems were n-butanol + phosphoric acid(PA) + water,methyl isobutyl ketone(MIBK) + PA + water,30% kerosene in tri-n-butylphosphate(TBP) + PA + water.The direction and intensity of mass transfer were adjusted by adding PA in one of two phases mutual saturated in advance.When PA transferred from the organic phase to the aqueous phase,tiny aqueous droplets may generate inside the organic phase by mass transfer inducement to form a new W/O/W flow pattern directly on some special cases.Once the PA concentration was very high,violent Marangoni effect could be observed to throw part of organic phase out of droplets as tail.The interphase transfer of PA could expand the jetting flow region,in particular for systems with low or medium inter-facial tension and when the mass transfer direction was from the aqueous phase to the organic phase.展开更多
In this work, flowerlike ZnO micro/nanostructures assembled from nanorods are obtained through a facile hydrothermal route. The experimental results indicated that the as-synthesized ZnO microflowers have an average d...In this work, flowerlike ZnO micro/nanostructures assembled from nanorods are obtained through a facile hydrothermal route. The experimental results indicated that the as-synthesized ZnO microflowers have an average diameter of 2 μm, composed of nanorods of an average diameter of 200 nm and a tapered morphology.ZnO with other morphologies were also obtained by varying the reaction conditions. Systematical conditiondependent experiments were conducted to reveal the growth mechansim of the microflowers. It is suggested that the zinc source types, solution p H value, and reaction temperature, as well as reaction time are responsible for the variations of ZnO morphology. Luminescence properties of ZnO microflowers were investigated through monitoring different parts of nanorods, showing good optical quality.展开更多
Objective\ The relationship between graft blood flow, epicardial microflow, mean arterial pressure and hemorheologic changes was studied during intraoperative heart failure. Methods\ These parameters were done to ...Objective\ The relationship between graft blood flow, epicardial microflow, mean arterial pressure and hemorheologic changes was studied during intraoperative heart failure. Methods\ These parameters were done to evaluate the use of repeated cardiopulmonary bypass support for the intraoperative heart failure following aorto coronary bypass surgery. Included in this study were 10 patients with a mean age of 70 and unstable angina undergoing coronary bypass grafting and suffering from intraoperative heart failure. The epicardiai microflow, graft flow, mean arterial pressure and blood cell filterability were measured. Resluts\ During heart failure, the mean arterial pressure fell by 41%(P<0.01), graft flow by 67%(P<0.01) and epicardialmicroflow by 64%(P<0.01). After 15 to 56 min of assisted cardiopulmonary bypass support, the epicardial microflow and graft flow were partially restored, while red cell and white cell filterability was reduced by 31% and 64% respectively (P<0.01). There were significant correlations between graft flow, epicardial microflow, blood cell filterability and cardiopulmonary bypass time. All patients recovered and were discharged from the hospital.Conclusion\ It is concluded that the use of temporary assisted CPB support to treat intrapoperative heart failure allows the recovery of the myocardium and thereby restores the mean arterial pressure. The recovery of graft flow and epicardial flow occurred to a lesser extent. The CPB support seemed to be suitable for about 60 min probably because of increasing disturbance to the blood cell filterability, graft flow and the epicardial microcirculation.\;展开更多
This paper reports that <em>α</em>-Bi<sub>2</sub>O<sub>3</sub> microflowers can be synthesized by an extremely simple and easy approach of inducing a reaction through the addition ...This paper reports that <em>α</em>-Bi<sub>2</sub>O<sub>3</sub> microflowers can be synthesized by an extremely simple and easy approach of inducing a reaction through the addition of NaOH aqueous solution to a mixed aqueous solution of Bi(NO<sub>3</sub>)<sub>3</sub>·5H<sub>2</sub>O and HNO<sub>3</sub> scanning electron microscopy images of the Bi<sub>2</sub>O<sub>3</sub> microflowers indicate that the Bi<sub>2</sub>O<sub>3</sub> nanorods grew radially from the centre of the microflower to form the microflower shape. The findings of this study show that control of the reaction temperature, reaction time, and raw material mixture ratio plays an important role in the formation of <em>α</em>-Bi<sub>2</sub>O<sub>3</sub> microflowers. It is especially revealed that <em>α</em>-Bi<sub>2</sub>O<sub>3</sub> microflowers can be formed at low temperatures with short reaction times. It has thus far been reported that flower-shaped Bi<sub>2</sub>O<sub>3</sub> particles or their precursors can be synthesized by the addition of additives such as organic molecules or certain inorganic ions. The present work reports on the discovery of ways to synthesize flower-shaped Bi<sub>2</sub>O<sub>3</sub> particles without the use of special additives.展开更多
N-formylation of amines,a class of synthetically important reactions,is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase t...N-formylation of amines,a class of synthetically important reactions,is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency.Here,an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine,which achieved a reaction yield of 82.97%and a selectivity of>99%at 12 min using cheap organic dye photocatalyst under mild reaction conditions.The influence of essential parameters,including light intensity,temperature and equivalents of the gas,additive and photocatalyst,on the reaction yield was systematically studied.Furthermore,kinetic investigations were conducted,exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity,temperature and photocatalyst equivalent.The microflow photocatalytic approach established in this work,which realized a markedly higher space-time yield than the conventional batch method(37.9 vs.0.212 mmol h-1 L-1),paves the way for the continuous,green and efficient synthesis of N-formamides.展开更多
Solar energy conversion and high-value chemical production are of utmost importance.However,the de-velopment of efficient photocatalysts with strong redox ability remains challenging.Here we report a unique 3D/0D In_(...Solar energy conversion and high-value chemical production are of utmost importance.However,the de-velopment of efficient photocatalysts with strong redox ability remains challenging.Here we report a unique 3D/0D In_(2)S_(3)/WO_(3)S-scheme heterojunction photocatalyst obtained by depositing WO_(3)quantum dots(QDs)onto hierarchical In_(2)S_(3)microflowers.The In_(2)S_(3)/WO_(3)composite exhibits outstanding visible light absorption,with a maximum optical response of up to 600 nm.The electronic interaction and charge separation at interfaces are explored by in situ X-ray photoelectron spectroscopy(XPS)and density func-tional theory(DFT)calculations.The difference in work function causes In_(2)S_(3)to donate electrons to WO_(3)upon combination,leading to the formation of an internal electric field(IEF)at the interfaces.Due to the IEF and bent energy bands,the transfer and separation of photogenerated charge carriers follow an S-scheme pathway within In_(2)S_(3)/WO_(3).Owing to the strong redox ability,spatial charge separation and lower H 2-generation barrier of S active sites,the optimized In_(2)S_(3)/WO_(3)heterojunctions show enhanced photocatalytic hydrogen evolution of 0.39 mmol h^(-1)g^(-1),6.7 times that of pristine In_(2)S_(3).In addition,the In_(2)S_(3)/WO_(3)S-scheme heterojunctions afford a remarkable activity for photocatalytic nitrobenzene hydro-genation with nearly 98%conversion and 99%selectivity of aniline within 1 h.Our work might present new insights into developing efficient S-scheme heterojunctions for various photocatalytic applications.展开更多
Nitrogen-doped carbon-coated hollow SnS_(2)/NiS(SnS_(2)/NiS@N–C)microflowers were obtained using NiSn(OH)6 nanospheres as the template via a solventthermal method followed by the polydopamine coating and carbonizatio...Nitrogen-doped carbon-coated hollow SnS_(2)/NiS(SnS_(2)/NiS@N–C)microflowers were obtained using NiSn(OH)6 nanospheres as the template via a solventthermal method followed by the polydopamine coating and carbonization process.When served as an anode material for lithium-ion batteries,such hollow SnS_(2)/NiS@N–C microflowers exhibited a capacity of 403.5 mAh·g^(−1) at 2.0 A·g^(−1) over 200 cycles and good rate performance.The electrochemical reaction kinetics of this anode was analyzed,and the morphologies and structures of anode materials after the cycling test were characterized.The high stability and good rate performance were mainly due to bimetallic synergy,hollow micro/nanostructure,and nitrogen-doped carbon layers.The revealed excellent electrochemical energy storage properties of hollow SnS_(2)/NiS@N–C microflowers in this study highlight their potential as the anode material.展开更多
Due to the rapid advances inmicro-electro-mechanical systems(MEMS),the study of microflows becomes increasingly important.Currently,the molecular-based simulation techniques are the most reliable methods for rarefied ...Due to the rapid advances inmicro-electro-mechanical systems(MEMS),the study of microflows becomes increasingly important.Currently,the molecular-based simulation techniques are the most reliable methods for rarefied flow computation,even though these methods face statistical scattering problem in the low speed limit.With discretized particle velocity space,a unified gas-kinetic scheme(UGKS)for entire Knudsen number flow has been constructed recently for flow computation.Contrary to the particle-based direct simulation Monte Carlo(DSMC)method,the unified scheme is a partial differential equation-based modeling method,where the statistical noise is totally removed.But,the common point between the DSMC and UGKS is that both methods are constructed through direct modeling in the discretized space.Due to the multiscale modeling in the unified method,i.e.,the update of both macroscopic flow variables and microscopic gas distribution function,the conventional constraint of time step being less than the particle collision time inmany direct Boltzmann solvers is released here.The numerical tests show that the unified scheme is more efficient than the particle-basedmethods in the low speed rarefied flow computation.Themain purpose of the current study is to validate the accuracy of the unified scheme in the capturing of non-equilibrium flow phenomena.In the continuum and free molecular limits,the gas distribution function used in the unified scheme for the flux evaluation at a cell interface goes to the corresponding Navier-Stokes and free molecular solutions.In the transition regime,the DSMC solution will be used for the validation of UGKS results.This study shows that the unified scheme is indeed a reliable and accurate flow solver for low speed non-equilibrium flows.It not only recovers the DSMC results whenever available,but also provides high resolution results in cases where the DSMC can hardly afford the computational cost.In thermal creep flow simulation,surprising solution,such as the gas flowing from hot to cold regions along the wall surface,is observed for the first time by the unified scheme,which is confirmed later through intensive DSMC computation.展开更多
Metal-organic frameworks(MOFs)with porous crystal structures have attracted extensive attention in application of energy storage and conversion,owing to their regularity,porosity,large specific surface area,etc.In thi...Metal-organic frameworks(MOFs)with porous crystal structures have attracted extensive attention in application of energy storage and conversion,owing to their regularity,porosity,large specific surface area,etc.In this work,Co-MOF-74 microflower has been successfully prepared via a controllable solvent regulation strategy.Through modulating the polarity of the solvent,crystals grow in certain preferred orientation and Co-MOF-74 with various morphologies were obtained.Thereinto,the energy storage performance of Co-MOF-74 microflower was measured in both three-electrode system and asymmetric supercapacitor device(specific capacitance of 164.2 F/g at 0.5 A/g in the three-electrode system and 62.5 F/g at 1 A/g in the asymmetric supercapacitor device).This can be attributed to the preferred crystal orientation resulting in a regular and uniform microflower,which is of great significance to electronic interfacial exchange and ion transfer during electrochemical reactions.展开更多
Cerium dioxide has a comparatively lower Ce4+/Ce3+redox pair,which leaves abundant oxygen vacancies on oxide lattice,also making incorporation of foreign ion and subsequent applications feasible and convenient.In this...Cerium dioxide has a comparatively lower Ce4+/Ce3+redox pair,which leaves abundant oxygen vacancies on oxide lattice,also making incorporation of foreign ion and subsequent applications feasible and convenient.In this work,a series of cerium-yttrium mixed oxides were prepared by using polyvinylpyrrolidone as major template through sol-gel,which were further employed as catalyst for dehydration of aniline with formic acid into N-phenylformamide.Characterizations reveal that synthetic samples have a variety of morphologies including nanoparticle,microflower,and uniform microrods.The monitoring of particle size,zeta potential,and ultravioletvisible(UV-Vis)of preparative solution indicate that selfassembly of polyvinylpyrrolidone and its subsequent reaction with metal ion determines sample morphology.In catalytic dehydration,all samples show high dehydration efficiencies that are comparable to those from anhydrous Na2SO4 and combination of dicyclohexylcarbodiimide with 4-dimethylaminopyridine and dichloromethane shows better outputs than water.In association with structural analysis,cerium looks more active than yttrium,while yttrium mainly plays as a structure-directing and poreformingagent.Thisstudymaycontributeto micro-/nanofabrication of rare earth composites and their catalytic applications.展开更多
Aligned silica nanowire arrays and silica microflowers were fabricated using boron as the catalyst and under the flow N2 gas. The obtained product had no catalyst contamination. And silica nanowires had long lengths o...Aligned silica nanowire arrays and silica microflowers were fabricated using boron as the catalyst and under the flow N2 gas. The obtained product had no catalyst contamination. And silica nanowires had long lengths of a few hundreds. The growth of nanowire arrays and microflowers was explained using mechanism. Parallel-plate capacitors using silica nanowire mat as the dielectric were fabricated. The silica nanowire capacitor shows a specific capacitance of 0.24 n F/cm~2 at the frequency of 100 Hz. The capacitor is not monotone changing with the frequency. The measurement of mechanical properties shows that the tunneling current increases along with an increase in bending angle of the capacitor.展开更多
基金financially supported by the National Natural Science Foundation of China (Grants. 22075279, 22279137, 22125903, 22109040)National Key R&D Program of China (Grant 2022YFA1504100)+2 种基金Dalian Innovation Support Plan for High Level Talents (2019RT09)Dalian National Labo- ratory For Clean Energy (DNL), CAS, DNL Cooperation Fund, CAS (DNL202016, DNL202019), DICP (DICP I2020032)the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy (YLU-DNL Fund 2021002, YLU- DNL Fund 2021009)。
文摘Planar Na ion micro-supercapacitors(NIMSCs) that offer both high energy density and power density are deemed to a promising class of miniaturized power sources for wearable and portable microelectron-ics. Nevertheless, the development of NIMSCs are hugely impeded by the low capacity and sluggish Na ion kinetics in the negative electrode.Herein, we demonstrate a novel carbon-coated Nb_(2)O_5 microflower with a hierarchical structure composed of vertically intercrossed and porous nanosheets, boosting Na ion storage performance. The unique structural merits, including uniform carbon coating, ultrathin nanosheets and abun-dant pores, endow the Nb_(2)O_5 microflower with highly reversible Na ion storage capacity of 245 mAh g^(-1) at 0.25 C and excellent rate capability.Benefiting from high capacity and fast charging of Nb_(2)O_5 microflower, the planar NIMSCs consisted of Nb_(2)O_5 negative electrode and activated car-bon positive electrode deliver high areal energy density of 60.7 μWh cm^(-2),considerable voltage window of 3.5 V and extraordinary cyclability. Therefore, this work exploits a structural design strategy towards electrode materials for application in NIMSCs, holding great promise for flexible microelectronics.
基金supported by Key Area Research and Development Program of Guangdong Province (2019B110209003)Guangdong Basic and Applied Basic Research Foundation (2019B1515120058,2020A1515011149)+2 种基金National Natural Science Foundation of China (22078374,21776324)National Key R&D Program of China (2018YFD0800703)National Ten Thousand Talent Plan,the Fundamental Research Funds for the Cornell University (19lgzd25)and Hundred Talent Plan (201602)from Sun Yat-sen University.
文摘A robust and green strategy for the selective upgrading of biomass-derived platform chemicals towards highly valuable products is important for the sustainable development.Herein,the efficient electrocatalytic oxidation of biomass-derived furfuryl alcohol(FFA)into furoic acid(FurAc)catalyzed by the electrodeposited non-precious NiFe microflowers was successfully reached under the low temperature and ambient pressure.The 3D hierarchical NiFe microflowers assembled from ultrathin nanosheets were controllably synthesized by the electrodeposition method and uniformly grown on carbon fiber paper(CFP).Electrochemical analysis confirmed that NiFe nanosheets more preferred in the selective oxidation of FFA(FFAOR)than oxygen evolution reaction(OER).The linear sweep voltammetry(LSV)in FFAOR displayed a clear decrease towards lower potential,resulting in 30 mV reduction of overpotential at 20 mA cm^(-2) compared with that of OER.The optimal catalyst Ni_(1)Fe_(2) nanosheets exhibited the highest selectivity of FurAc(94.0%)and 81.4%conversion of FFA within 3 h.Besides,the influence of various reaction parameters on FFAOR was then explored in details.After that,the reaction pathway was investigated and rationally proposed.The outstanding performance for FFAOR can be ascribed to the unique structure of 3D flower-like NiFe nanosheets and oxygen vacancies,resulting in large exposure of active sites,faster electron transfer and enhanced adsorption of reactants.Our findings highlight a facile and convenient mean with a promising green future,which is promising for processing of various biomass-derived platform chemicals into value-added products.
基金Project (51005053) supported by the National Science Foundation for Young Scientists of China
文摘By means of similar physical simulation, liquid metal filling flow pattern in the microscale during the centrifugal casting process was studied. It was found that, in microscale, the flow channel with the maximum cross-sectional area was filled first, and the micro flow channels with 0.1 mm in diameter were filled when the rotational speed was increased to 964 r/min. The total fluid energy remained constant during the mould filling, and the changes of cross-sectional area only occurred in the microflow channels with 0.3 mm in diameter. Filling velocity increased with processing time, and a peak value was achieved rapidly, followed by a gentle increase as the process proceeded further. The time required to achieve the peak filling rate decreased dramatically with increase of rotational speed.
基金supported by the National Natural Science Foundation of China (Nos. 21325417 and 51533008)National Key R&D Program of China (No. 2016YFA0200200)Fundamental Research Funds for the Central Universities (2017XZZX008-06)
文摘Graphene has shown great potential in microwave absorption(MA) owing to its high surface area, low density,tunable electrical conductivity and good chemical stability.To fully realize graphenes& MA ability, the microstructure of graphene should be carefully addressed. Here we prepared graphene microflowers(Gmfs) with highly porous structure for high-performance MA filler material. The efficient absorption bandwidth(reflection loss B-10 dB) reaches 5.59 GHz and the minimum reflection loss is up to -42.9 dB, showing significant increment compared with stacked graphene. Such performance is higher than most graphene-based materials in the literature. Besides, the low filling content(10 wt%) and low density(40–50 mg cm^(-3))are beneficial for the practical applications. Without compounding with magnetic materials or conductive polymers,Gmfs show outstanding MA performance with the aid of rational microstructure design. Furthermore, Gmfs exhibit advantages in facile processibility and large-scale production compared with other porous graphene materials including aerogels and foams.
基金Supported by the National Natural Science Foundation of China (20525622,20876084)the National Basic Research Program of China (2007CB714302)
文摘This paper presents the experimental results of liquid-liquid microflows in a coaxial microfluidic device with mass transfer.Three working systems were n-butanol + phosphoric acid(PA) + water,methyl isobutyl ketone(MIBK) + PA + water,30% kerosene in tri-n-butylphosphate(TBP) + PA + water.The direction and intensity of mass transfer were adjusted by adding PA in one of two phases mutual saturated in advance.When PA transferred from the organic phase to the aqueous phase,tiny aqueous droplets may generate inside the organic phase by mass transfer inducement to form a new W/O/W flow pattern directly on some special cases.Once the PA concentration was very high,violent Marangoni effect could be observed to throw part of organic phase out of droplets as tail.The interphase transfer of PA could expand the jetting flow region,in particular for systems with low or medium inter-facial tension and when the mass transfer direction was from the aqueous phase to the organic phase.
基金supported by the Foundation for Key Project of Ministry of Education, China (No. 211046)Open Fund of State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Dong Hua University (No. K1012)+1 种基金Open Fund State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University (No. 201222)Program for New Century Excellent Talents in Heilongjiang Provincial University
文摘In this work, flowerlike ZnO micro/nanostructures assembled from nanorods are obtained through a facile hydrothermal route. The experimental results indicated that the as-synthesized ZnO microflowers have an average diameter of 2 μm, composed of nanorods of an average diameter of 200 nm and a tapered morphology.ZnO with other morphologies were also obtained by varying the reaction conditions. Systematical conditiondependent experiments were conducted to reveal the growth mechansim of the microflowers. It is suggested that the zinc source types, solution p H value, and reaction temperature, as well as reaction time are responsible for the variations of ZnO morphology. Luminescence properties of ZnO microflowers were investigated through monitoring different parts of nanorods, showing good optical quality.
文摘Objective\ The relationship between graft blood flow, epicardial microflow, mean arterial pressure and hemorheologic changes was studied during intraoperative heart failure. Methods\ These parameters were done to evaluate the use of repeated cardiopulmonary bypass support for the intraoperative heart failure following aorto coronary bypass surgery. Included in this study were 10 patients with a mean age of 70 and unstable angina undergoing coronary bypass grafting and suffering from intraoperative heart failure. The epicardiai microflow, graft flow, mean arterial pressure and blood cell filterability were measured. Resluts\ During heart failure, the mean arterial pressure fell by 41%(P<0.01), graft flow by 67%(P<0.01) and epicardialmicroflow by 64%(P<0.01). After 15 to 56 min of assisted cardiopulmonary bypass support, the epicardial microflow and graft flow were partially restored, while red cell and white cell filterability was reduced by 31% and 64% respectively (P<0.01). There were significant correlations between graft flow, epicardial microflow, blood cell filterability and cardiopulmonary bypass time. All patients recovered and were discharged from the hospital.Conclusion\ It is concluded that the use of temporary assisted CPB support to treat intrapoperative heart failure allows the recovery of the myocardium and thereby restores the mean arterial pressure. The recovery of graft flow and epicardial flow occurred to a lesser extent. The CPB support seemed to be suitable for about 60 min probably because of increasing disturbance to the blood cell filterability, graft flow and the epicardial microcirculation.\;
文摘This paper reports that <em>α</em>-Bi<sub>2</sub>O<sub>3</sub> microflowers can be synthesized by an extremely simple and easy approach of inducing a reaction through the addition of NaOH aqueous solution to a mixed aqueous solution of Bi(NO<sub>3</sub>)<sub>3</sub>·5H<sub>2</sub>O and HNO<sub>3</sub> scanning electron microscopy images of the Bi<sub>2</sub>O<sub>3</sub> microflowers indicate that the Bi<sub>2</sub>O<sub>3</sub> nanorods grew radially from the centre of the microflower to form the microflower shape. The findings of this study show that control of the reaction temperature, reaction time, and raw material mixture ratio plays an important role in the formation of <em>α</em>-Bi<sub>2</sub>O<sub>3</sub> microflowers. It is especially revealed that <em>α</em>-Bi<sub>2</sub>O<sub>3</sub> microflowers can be formed at low temperatures with short reaction times. It has thus far been reported that flower-shaped Bi<sub>2</sub>O<sub>3</sub> particles or their precursors can be synthesized by the addition of additives such as organic molecules or certain inorganic ions. The present work reports on the discovery of ways to synthesize flower-shaped Bi<sub>2</sub>O<sub>3</sub> particles without the use of special additives.
基金the financial support from the National Natural Science Foundation of China(No.21808059)the Fundamental Research Funds for the Central Universities(No.JKA01221712).
文摘N-formylation of amines,a class of synthetically important reactions,is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency.Here,an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine,which achieved a reaction yield of 82.97%and a selectivity of>99%at 12 min using cheap organic dye photocatalyst under mild reaction conditions.The influence of essential parameters,including light intensity,temperature and equivalents of the gas,additive and photocatalyst,on the reaction yield was systematically studied.Furthermore,kinetic investigations were conducted,exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity,temperature and photocatalyst equivalent.The microflow photocatalytic approach established in this work,which realized a markedly higher space-time yield than the conventional batch method(37.9 vs.0.212 mmol h-1 L-1),paves the way for the continuous,green and efficient synthesis of N-formamides.
基金funded by the Opening Project of Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention(LAP 3)(No.FDLAP21008)the Hubei Provincial Natural Science Foundation of China(No.2020CFB785)+1 种基金the Science and Tech-nology Research Project of the Education Department of Hubei Province(No.D20191703)the Project of Hubei Key Labora-tory of Biomass Fibers and Eco-dyeing&Finishing(WTU)(Nos.STRZ202219,STRZ202220).
文摘Solar energy conversion and high-value chemical production are of utmost importance.However,the de-velopment of efficient photocatalysts with strong redox ability remains challenging.Here we report a unique 3D/0D In_(2)S_(3)/WO_(3)S-scheme heterojunction photocatalyst obtained by depositing WO_(3)quantum dots(QDs)onto hierarchical In_(2)S_(3)microflowers.The In_(2)S_(3)/WO_(3)composite exhibits outstanding visible light absorption,with a maximum optical response of up to 600 nm.The electronic interaction and charge separation at interfaces are explored by in situ X-ray photoelectron spectroscopy(XPS)and density func-tional theory(DFT)calculations.The difference in work function causes In_(2)S_(3)to donate electrons to WO_(3)upon combination,leading to the formation of an internal electric field(IEF)at the interfaces.Due to the IEF and bent energy bands,the transfer and separation of photogenerated charge carriers follow an S-scheme pathway within In_(2)S_(3)/WO_(3).Owing to the strong redox ability,spatial charge separation and lower H 2-generation barrier of S active sites,the optimized In_(2)S_(3)/WO_(3)heterojunctions show enhanced photocatalytic hydrogen evolution of 0.39 mmol h^(-1)g^(-1),6.7 times that of pristine In_(2)S_(3).In addition,the In_(2)S_(3)/WO_(3)S-scheme heterojunctions afford a remarkable activity for photocatalytic nitrobenzene hydro-genation with nearly 98%conversion and 99%selectivity of aniline within 1 h.Our work might present new insights into developing efficient S-scheme heterojunctions for various photocatalytic applications.
基金funded by the National Research Foundation of Korea(Grant No.NRF-2019R1A5A8080290)the University Synergy Innovation Program of Anhui Province(GXXT-2020-073 and GXXT-2020-074).
文摘Nitrogen-doped carbon-coated hollow SnS_(2)/NiS(SnS_(2)/NiS@N–C)microflowers were obtained using NiSn(OH)6 nanospheres as the template via a solventthermal method followed by the polydopamine coating and carbonization process.When served as an anode material for lithium-ion batteries,such hollow SnS_(2)/NiS@N–C microflowers exhibited a capacity of 403.5 mAh·g^(−1) at 2.0 A·g^(−1) over 200 cycles and good rate performance.The electrochemical reaction kinetics of this anode was analyzed,and the morphologies and structures of anode materials after the cycling test were characterized.The high stability and good rate performance were mainly due to bimetallic synergy,hollow micro/nanostructure,and nitrogen-doped carbon layers.The revealed excellent electrochemical energy storage properties of hollow SnS_(2)/NiS@N–C microflowers in this study highlight their potential as the anode material.
基金Hong Kong Research Grant Council(621709,621011)and grants SRFI11SC05 and RPC10SC11 atHKUST.J.C.Huang was supported by National Science Council of Taiwan through grant No.NSC 100-2221-E-019-048-MY3.
文摘Due to the rapid advances inmicro-electro-mechanical systems(MEMS),the study of microflows becomes increasingly important.Currently,the molecular-based simulation techniques are the most reliable methods for rarefied flow computation,even though these methods face statistical scattering problem in the low speed limit.With discretized particle velocity space,a unified gas-kinetic scheme(UGKS)for entire Knudsen number flow has been constructed recently for flow computation.Contrary to the particle-based direct simulation Monte Carlo(DSMC)method,the unified scheme is a partial differential equation-based modeling method,where the statistical noise is totally removed.But,the common point between the DSMC and UGKS is that both methods are constructed through direct modeling in the discretized space.Due to the multiscale modeling in the unified method,i.e.,the update of both macroscopic flow variables and microscopic gas distribution function,the conventional constraint of time step being less than the particle collision time inmany direct Boltzmann solvers is released here.The numerical tests show that the unified scheme is more efficient than the particle-basedmethods in the low speed rarefied flow computation.Themain purpose of the current study is to validate the accuracy of the unified scheme in the capturing of non-equilibrium flow phenomena.In the continuum and free molecular limits,the gas distribution function used in the unified scheme for the flux evaluation at a cell interface goes to the corresponding Navier-Stokes and free molecular solutions.In the transition regime,the DSMC solution will be used for the validation of UGKS results.This study shows that the unified scheme is indeed a reliable and accurate flow solver for low speed non-equilibrium flows.It not only recovers the DSMC results whenever available,but also provides high resolution results in cases where the DSMC can hardly afford the computational cost.In thermal creep flow simulation,surprising solution,such as the gas flowing from hot to cold regions along the wall surface,is observed for the first time by the unified scheme,which is confirmed later through intensive DSMC computation.
基金supported by the National Natural Science Foundation of China(Nos.U1904215,21671170,21673203)the Topnotch Academic Programs Project of Jiangsu Higher Education Institutions(TAPP)+2 种基金Changjiang scholars program of the Ministry of Education(No.Q2018270)Excellent doctoral dissertation of Yangzhou universityUndergraduate scientific research innovation projects in Jiangsu province(No.201911117036Z)。
文摘Metal-organic frameworks(MOFs)with porous crystal structures have attracted extensive attention in application of energy storage and conversion,owing to their regularity,porosity,large specific surface area,etc.In this work,Co-MOF-74 microflower has been successfully prepared via a controllable solvent regulation strategy.Through modulating the polarity of the solvent,crystals grow in certain preferred orientation and Co-MOF-74 with various morphologies were obtained.Thereinto,the energy storage performance of Co-MOF-74 microflower was measured in both three-electrode system and asymmetric supercapacitor device(specific capacitance of 164.2 F/g at 0.5 A/g in the three-electrode system and 62.5 F/g at 1 A/g in the asymmetric supercapacitor device).This can be attributed to the preferred crystal orientation resulting in a regular and uniform microflower,which is of great significance to electronic interfacial exchange and ion transfer during electrochemical reactions.
基金the Natural Science Foundation of Shaanxi Province(No.2017JM2016)the Fundamental Research Funds for the Central Universities(No.xjj2014005)。
文摘Cerium dioxide has a comparatively lower Ce4+/Ce3+redox pair,which leaves abundant oxygen vacancies on oxide lattice,also making incorporation of foreign ion and subsequent applications feasible and convenient.In this work,a series of cerium-yttrium mixed oxides were prepared by using polyvinylpyrrolidone as major template through sol-gel,which were further employed as catalyst for dehydration of aniline with formic acid into N-phenylformamide.Characterizations reveal that synthetic samples have a variety of morphologies including nanoparticle,microflower,and uniform microrods.The monitoring of particle size,zeta potential,and ultravioletvisible(UV-Vis)of preparative solution indicate that selfassembly of polyvinylpyrrolidone and its subsequent reaction with metal ion determines sample morphology.In catalytic dehydration,all samples show high dehydration efficiencies that are comparable to those from anhydrous Na2SO4 and combination of dicyclohexylcarbodiimide with 4-dimethylaminopyridine and dichloromethane shows better outputs than water.In association with structural analysis,cerium looks more active than yttrium,while yttrium mainly plays as a structure-directing and poreformingagent.Thisstudymaycontributeto micro-/nanofabrication of rare earth composites and their catalytic applications.
基金financially supported by the National Natural Science Foundation of China (No. 61404036)the National Basic Research Program of China (No. 2012CB934104)+1 种基金the Fundamental Research Funds for the Central Universities (Nos. HIT. NSRIF.2015039, 01508536)State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology (No. 2016 TS 06)
文摘Aligned silica nanowire arrays and silica microflowers were fabricated using boron as the catalyst and under the flow N2 gas. The obtained product had no catalyst contamination. And silica nanowires had long lengths of a few hundreds. The growth of nanowire arrays and microflowers was explained using mechanism. Parallel-plate capacitors using silica nanowire mat as the dielectric were fabricated. The silica nanowire capacitor shows a specific capacitance of 0.24 n F/cm~2 at the frequency of 100 Hz. The capacitor is not monotone changing with the frequency. The measurement of mechanical properties shows that the tunneling current increases along with an increase in bending angle of the capacitor.
