Sunscreen agents derived from plants have been regarded as promising alternatives to artificial compounds.In this work,carbon dots(CDs)were prepared from carrot juice via a continuous microflowbased approach,where the...Sunscreen agents derived from plants have been regarded as promising alternatives to artificial compounds.In this work,carbon dots(CDs)were prepared from carrot juice via a continuous microflowbased approach,where the influence of process parameters was studied and optimized.Complimentary characterization revealed the CDs not only have small size,narrow size distribution,and good water solubility,but also have abundant functional groups as well as excellent UV absorption performance.Relying on these properties,the CDs were used as UV absorbers,suggesting they have strong long-term UV absorption ability over a broad pH range.The UV-absorption properties of the CDs were confirmed by incorporating the CDs in polyvinyl alcohol(PVA)to get C-CDs@PVA films of different thickness,in which significantly enhanced UV absorption performance was observed.Besides,the sun protection performance is also related to the film thickness.Afterwards,the practical application of the CDs was evaluated by adding them in a typical skin cream.With the addition of the CDs,the cream has drastically reduced UV transmittance in both UVA and UVB regions,and exhibits better UV absorption performance than commercial sunscreen agents.The CDs also demonstrated low cytotoxicity and high DPPH radical scavenging activity,making them promising as green sunscreen absorbers.This work is expected to provide a guidance for the development of green and effective natural sunscreen agents via microflowbased method.展开更多
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
VS_(2) has attracted increasing attention as a cathode material for aqueous zinc ion batteries because of its proper large layer spacing,weak interlayer interactions,multiple valence states of V,and excellent electric...VS_(2) has attracted increasing attention as a cathode material for aqueous zinc ion batteries because of its proper large layer spacing,weak interlayer interactions,multiple valence states of V,and excellent electrical conductivity,but its large volume change during charging and discharging leads to poor cycling stability.Herein,we report a one-step hydrothermal synthesis of VS_(2) microflowers with proper lamellar spacing,which provides a stable framework for the insertion/deinsertion of zinc ions and enhances the cycling stability,delivering an initial charge capacity of 128.3 mAh g^(-1) at 3 A g^(-1) and maintains a charge capacity of 100.1 mAh g^(-1) after 900 cycles.In addition,the optimized VS_(2) cathode shows specific capacities of 215.7 and 150.5 mAh g^(-1) at the current densities of 0.1 and 2 A g^(-1),respectively,demonstrating that the microflower structure with a high specific surface area and a short diffusion distance also significantly enhances the rate performance.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
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
Zinc oxide(ZnO)serves as a crucial functional semiconductor with a wide direct bandgap of approximately 3.37 eV.Solvothermal reaction is commonly used in the synthesis of ZnO micro/nanostructures,given its low cost,si...Zinc oxide(ZnO)serves as a crucial functional semiconductor with a wide direct bandgap of approximately 3.37 eV.Solvothermal reaction is commonly used in the synthesis of ZnO micro/nanostructures,given its low cost,simplicity,and easy implementation.Moreover,ZnO morphology engineering has become desirable through the alteration of minor conditions in the reaction process,particularly at room temperature.In this work,ZnO micro/nanostructures were synthesized in a solution by varying the amounts of the ammonia added at low temperatures(including room temperature).The formation of Zn^(2+)complexes by ammonia in the precursor regulated the reaction rate of the morphology engineering of ZnO,which resulted in various structures,such as nanoparticles,nanosheets,microflowers,and single crystals.Finally,the obtained ZnO was used in the optoelectronic application of ultraviolet detectors.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
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
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National Natural Science Foundation of China(22078125)Postdoctoral Science Foundation of China(2023M741472)Fundamental Research Funds for the Central Universities(JUSRP622038).
文摘Sunscreen agents derived from plants have been regarded as promising alternatives to artificial compounds.In this work,carbon dots(CDs)were prepared from carrot juice via a continuous microflowbased approach,where the influence of process parameters was studied and optimized.Complimentary characterization revealed the CDs not only have small size,narrow size distribution,and good water solubility,but also have abundant functional groups as well as excellent UV absorption performance.Relying on these properties,the CDs were used as UV absorbers,suggesting they have strong long-term UV absorption ability over a broad pH range.The UV-absorption properties of the CDs were confirmed by incorporating the CDs in polyvinyl alcohol(PVA)to get C-CDs@PVA films of different thickness,in which significantly enhanced UV absorption performance was observed.Besides,the sun protection performance is also related to the film thickness.Afterwards,the practical application of the CDs was evaluated by adding them in a typical skin cream.With the addition of the CDs,the cream has drastically reduced UV transmittance in both UVA and UVB regions,and exhibits better UV absorption performance than commercial sunscreen agents.The CDs also demonstrated low cytotoxicity and high DPPH radical scavenging activity,making them promising as green sunscreen absorbers.This work is expected to provide a guidance for the development of green and effective natural sunscreen agents via microflowbased method.
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financially supported by the Ningbo Natural Science Foundation(No.202003N4054)the Fundamental Research Funds for the Central Universities.
文摘VS_(2) has attracted increasing attention as a cathode material for aqueous zinc ion batteries because of its proper large layer spacing,weak interlayer interactions,multiple valence states of V,and excellent electrical conductivity,but its large volume change during charging and discharging leads to poor cycling stability.Herein,we report a one-step hydrothermal synthesis of VS_(2) microflowers with proper lamellar spacing,which provides a stable framework for the insertion/deinsertion of zinc ions and enhances the cycling stability,delivering an initial charge capacity of 128.3 mAh g^(-1) at 3 A g^(-1) and maintains a charge capacity of 100.1 mAh g^(-1) after 900 cycles.In addition,the optimized VS_(2) cathode shows specific capacities of 215.7 and 150.5 mAh g^(-1) at the current densities of 0.1 and 2 A g^(-1),respectively,demonstrating that the microflower structure with a high specific surface area and a short diffusion distance also significantly enhances the rate performance.
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funded by the National Natural Science F oundation of China(No.52172205)。
文摘Zinc oxide(ZnO)serves as a crucial functional semiconductor with a wide direct bandgap of approximately 3.37 eV.Solvothermal reaction is commonly used in the synthesis of ZnO micro/nanostructures,given its low cost,simplicity,and easy implementation.Moreover,ZnO morphology engineering has become desirable through the alteration of minor conditions in the reaction process,particularly at room temperature.In this work,ZnO micro/nanostructures were synthesized in a solution by varying the amounts of the ammonia added at low temperatures(including room temperature).The formation of Zn^(2+)complexes by ammonia in the precursor regulated the reaction rate of the morphology engineering of ZnO,which resulted in various structures,such as nanoparticles,nanosheets,microflowers,and single crystals.Finally,the obtained ZnO was used in the optoelectronic application of ultraviolet detectors.
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.
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.
