Dear Editor, Nanosized particulate systems combining better cancer diagnosis with therapeutic effect are being designed based on the merging of nanotechnology with cellular and molecular techniques. The surface of the...Dear Editor, Nanosized particulate systems combining better cancer diagnosis with therapeutic effect are being designed based on the merging of nanotechnology with cellular and molecular techniques. The surface of these nanoscale carriers is often functionalized with biological molecules for stabilization and targeted delivery. The combinations of nano-core and associated functional molecules can cross the cell membrane [1], and the surface of nanomaterials （including coating and associated functional molecules） plays a critical role in determining the outcome of their interactions with cells [2, 3]. Studying the potential effects of nanomaterials in biological systems often requires the administration of nanoparticles into a cell culture system or into living organisms in vivo. It should be noted, however, that under such conditions nanopaticles are known to adsorb proteins from the biological system,展开更多
In this work,Fe/Ni nanoparticles were produced through Fe(II)and Ni(II)reduction by NaBH4 and they were stabilized by a kind of prepared granular adsorbent(Fe/Ni@PGA).Fe/Ni@PGA as an environment-friendly activator was...In this work,Fe/Ni nanoparticles were produced through Fe(II)and Ni(II)reduction by NaBH4 and they were stabilized by a kind of prepared granular adsorbent(Fe/Ni@PGA).Fe/Ni@PGA as an environment-friendly activator was used to activate persulfate(PS)for the removal of ciprofloxacin from aqueous solution.Fe/Ni@PGA was systematically characterized via Brunauer-Emmett-Teller(BET)method,X-ray diffraction(XRD),scanning electron microscopy(SEM),and Fourier transform infrared spectroscopy(FTIR).The effects of PS concentration,initial solution pH,Fe/Ni@PGA dosage,initial ciprofloxacin concentration,reaction temperature,anions,and natural organic matters on the removal of ciprofloxacin by Fe/Ni@PGA/PS were analyzed.The removal efficiency of ciprofloxacin by Fe/Ni@PGA/PS was 93.24%under an initial pH of 3.0,PS concentration of 10 mM,Fe/Ni@PGA dosage of 0.1 g,and reaction temperature of 30℃.Fe/Ni@PGA could still exhibit high catalytic activity after nine cycles of regeneration.The removal mechanisms for ciprofloxacin by the Fe/Ni@PGA/PS system were proposed.In summary,the Fe/Ni@PGA/PS system could be applied as a promising technology for ciprofloxacin removal.展开更多
Due to high efficiency,high controllability,high integration,lightweight,and other advantages,electric vehicle with hub motor driving technology has become an emerging trend of chassis technology.This paper concludes ...Due to high efficiency,high controllability,high integration,lightweight,and other advantages,electric vehicle with hub motor driving technology has become an emerging trend of chassis technology.This paper concludes the current state⁃of⁃the⁃art of hub motor drive technologies.Firstly,it summarizes recent hub motor drive products and makes suggestions for hub motor drive schemes in different application scenarios.Then research on hub motor drive key technologies such as integrated design,thermal optimization,lightweight,and intensity optimization is investigated.Considering the high response accuracy and zero delay characteristic of hub motor driving system combined with advanced distributed dynamics control technology that can further improve vehicle performance,this paper also analyzes existing chassis dynamics control technologies of hub motor driving system.Considering the development trend of vehicle electrification,intelligentization,network connection,and current research,this paper makes some forecasts for hub motor drive technologies development in the conclusion.展开更多
In order to understand the dnve-in target in a D-D type neutron generator,it is essential to study the mechanism of the interaction between hydrogen ion beams and the hydrogenabsorbing metal film.The present research ...In order to understand the dnve-in target in a D-D type neutron generator,it is essential to study the mechanism of the interaction between hydrogen ion beams and the hydrogenabsorbing metal film.The present research concerns the nucleation of hydride within zirconium film implanted with hydrogen ions.Doses of 30 keV hydrogen ions ranging from 4.30×10^（17） to1.43×10^（18） ions cm^（-2） were loaded into the zirconium film through the ion beam implantation technique.Features of the surface morphology and transformation of phase structures were investigated with scanning electron microscopy,atomic force microscopy and x-ray diffraction.Confirmation of the formation of 5 phase zirconium hydride in the implanted samples was first made by x-ray diffraction,and the different stages in the gradual nucleation and growth of zirconium hydride were then observed by atomic force microscope and scanning electron microscopy.展开更多
[Objectives]This study was conducted to construct a pColdI-HSP70 recombinant prokaryotic expression vector.[Methods]With rice‘N22’as the test variety,hydroponic experiments were set up for rice seedlings with normal...[Objectives]This study was conducted to construct a pColdI-HSP70 recombinant prokaryotic expression vector.[Methods]With rice‘N22’as the test variety,hydroponic experiments were set up for rice seedlings with normal growth(CK),high temperature treatment(H),drought treatment(D)and drought-high temperature cross treatment(DH).The recombinant prokaryotic expression vector was constructed by the method of prokaryotic expression,and its induction expression time,IPTG concentration and temperature were optimized.[Results]The pColdI-HSP70 expression vector was successfully constructed,and the fusion protein was highly expressed in host strain BL21,and the expressed proteins were all in a soluble form.By optimizing the induction expression conditions,it was found that the optimal expression conditions were the IPTG concentration of 0.5 mmol/L and induction at 20℃for 36 h.The expression analysis of the rice HSP70 gene under different stress treatments was carried out by qRT-PCR technology,and it was found that H,D and DH stresses all could induce its expression,and its expression levels were 4.65,1.40 and 17.66 times higher than that of the CK group,respectively.[Conclusions]This study lays a solid foundation for the isolation,purification and functional study of rice HSP70 proteins.展开更多
At present, there are significant regional differences in average life expectancy among countries in the world. Not only is there a great disparity in average life expectancy, but also the gender difference is positiv...At present, there are significant regional differences in average life expectancy among countries in the world. Not only is there a great disparity in average life expectancy, but also the gender difference is positive and negative, and is distributed in a bipolar distribution of “long life in rich countries and short life in poor countries”. This paper analyzes the factors affecting the life grade by using the ordered multivariate discrete selection model and combined with the average life expectancy data of countries all over the world in 2017. The test results show that: 1) The growth of per capita GDP, elderly dependency ratio and the proportion of people using at least basic drinking water services can effectively improve the level of life expectancy;2) The birth rate has an inhibitory effect on the average life expectancy;3) Through model comparison, probit model is more suitable for the analysis of this kind of problems than logit model, and the properties of the obtained model are better.展开更多
Carbon-sulfur composites have draw n in creasing interest in various fields including electrocatalysis because of their unique structures.However,carb on-sulfur composite with tiny sulfur nano crystals has still recei...Carbon-sulfur composites have draw n in creasing interest in various fields including electrocatalysis because of their unique structures.However,carb on-sulfur composite with tiny sulfur nano crystals has still received little attention.Herein,hollow porous carb on sphere-sulfur composite(HPCS-S)which possesses excellent electrochemical performance towards H2O2 has been prepared for the first time via a simple silica template method.The 2-5 nm sulfur nan ocrystals being restricted in the cha nnel of the hollow porous carb on spheres are un der a strong compressive stress,which was further con firmed by high-resoluti on tran smissi on electr on microscopy(HRTEM)and GPA.The HPCS-S nano crystals show better con ductivity tha n amorphous sulfur clusters because of the reducti on of the steric hindrance which efficie ntly promotes the electron transportation.Consequently,the higher activity and selectivity towards the 2e^oxygen reduction reaction(ORR)to H2O2 in alkaline solution was obtained.The H2O2 selectivity rises from 20%to over 70%after the sulfur addition and the H2O2 production rate achieves 183.99 mmol-gcataiyst-1 with the Faradaic efficiency of 70%.Furthermore,performance enhancement mechanism was also investigated using the den sity functional theory(DFT)calculatio ns.After the in troduci ng of sulfur nano crystals,the appeara nee of S-S bond greatly decreases the overpotential compared with S-doping,which results in significant enhancement of the electrocatalytic property.Consequently,the HPCS-S can be an efficient H2O2 production electrocatalyst in alkaline solution.展开更多
Developing efficient and low-cost electrocatalysts for oxygen evolution reaction(OER)with high electrochemical activity and durability for diverse renewable and sustainable energy technologies remains challenging.Here...Developing efficient and low-cost electrocatalysts for oxygen evolution reaction(OER)with high electrochemical activity and durability for diverse renewable and sustainable energy technologies remains challenging.Herein,an ultrasonic-assisted and coordination modulation strategy is developed to construct sandwich-like metal-organic framework(MOF)derived hydroxide nanosheet(NS)arrays/graphene oxide(GO)composite via one-step self-transformation route.Inducing from unsteady state,the dodecahedral ZIF-67 with Co^2+in tetrahedral coordination auto-converts into defect-rich ultrathin layered hydroxides with the interlayered ion NO3-.The self-transforming a-Co(OH)2/GO nanosheet arrays from ZIF-67(Co(OH)2-GNS)change the coordination mode of Co^2+and bring about the exposure of more metal active sites,thereby enhancing the spatial utilization ratio within the framework.As monometal-based electrocatalyst,the optimized Co(OH)2-GNS exhibits remarkable OER catalytic performance evidenced by a low overpotential of 259 mV to achieve a current density of 10 mA·cm-2 in alkaline medium,even exceeding commercial RuO2.During the oxygen evolution process,electron migration can be accelerated by the interfacial/in-plane charge polarization and local electric field,corroborated by the off-axis electron holography.Density functional theory(DFT)calculations further studied the collaboration between ultrathin Co(OH)2 NS and GO,which leads to lower energy barriers of intermediate products and greatly promotes electrocatalytic property.展开更多
Design and fabrication of cost-effective transition metal and their oxides-based nanocomposites are of paramount significance for metal-air batteries and water-splitting.However,the traditional optimized designs for n...Design and fabrication of cost-effective transition metal and their oxides-based nanocomposites are of paramount significance for metal-air batteries and water-splitting.However,the traditional optimized designs for nanostructure are complicated,low-efficient and underperform for wide-scale applications.Herein,a novel hierarchical framework of hollow Ni/NiFe2O4-CNTs compositemicrosphere forcibly-assembled by zero-dimensional(OD)Ni/NiFo204 nanoparticle(<16 nm)and one-dimensional(1D)self-supporting CNTs was fabricated successfully.Benefitted from the unique nanostructure,such monohybrids can achieve remarkable oxygen evolution reaction(OER)performance in alkaline media with a low overpotential and superior durability,which exceeds most of the commercial catalysts based on IrO/RuO2 or other non-noble metal nanomaterials.The enhanced OER performance of Ni/NiFe2OA-CNTs composite is mainly ascribed to the increased catalytic activity and the optimized conductivity induced by the effects of strong hierarchical coupling and charge transfers between CNTs and Ni/NiFe204 nanoparticles.These effects are greatly boosted by the polarized heterojunction interfaces confirmed by electron holography.The density functional theory(DFT)calculation indicates the epitaxial Ni further enriches the intrinsic electrons contents of NiFe204 and thus accelerates absorption/desorption kinetics of OER intermediates.This work hereby paves a facile route to construct the hollow composite microsphere with excellent OER electrocatalytic activity based on non-noble metal oxide/CNTs.展开更多
Manganese selenide （MnSe） possesses unique magnetic properties as an important magnetic semiconductor, but the synthesis and properties of MnSe nanocrystals are less developed compared to other semiconductor nanocry...Manganese selenide （MnSe） possesses unique magnetic properties as an important magnetic semiconductor, but the synthesis and properties of MnSe nanocrystals are less developed compared to other semiconductor nanocrystals because of the inability to obtain high-quality MnSe, especially in the metastable wurtzite structure. Here, we have successfully fabricated wurtzite MnSe nanocrystals via a colloidal approach which affords uniform crystal sizes and tailored shapes. The selective binding strength of the amine surfactant is the determining factor in shape-control and shape-evolution. Bullet-shapes could be transformed into shuttle-shapes if part of the oleylamine in the reaction solution was replaced by trioctylamine, and tetrapod-shaped nanocrystals could be formed in trioctylamine systems. The three-dimensional （3D） structure of the bullet-shaped nanorods has been demonstrated by the advanced transmission electron microscope （TEM） 3D-tomography technology. High-resolution TEM （HRTEM） and electron energy-loss spectroscopy （EELS） show that planar-defect structures such as stacking faults and twinning along the [001] direction arise during the growth of bullet-shapes. On the basis of careful HRTEM observations, we propose a ＂quadra-twin core＂ growth mechanism for the formation of wurtzite MnSe nanotetrapods. Furthermore, the wurtzite MnSe nanocrystals show low- temperature surface spin-glass behavior due to their noncompensated surface spins and the blocking temperatures increase from 8.4 K to 18.5 K with increasing surface area/volume ratio of the nanocrystals. Our results provide a systematic study of wurtzite MnSe nanocrystals.展开更多
The hollow porous structure with exceptional interfacial effect and customizable internal environment shows significant potential for application as electromagnetic shielding and absorption materials.However,designing...The hollow porous structure with exceptional interfacial effect and customizable internal environment shows significant potential for application as electromagnetic shielding and absorption materials.However,designing hollow porous electromagnetic absorbers with both desirable impedance matching and high loss capability remains a challenge.Herein,3D hollow porous electromagnetic microspheres were constructed by assembling 0D Co magnetic nanoparticles,1D carbon nanotubes,and 2D carbon nanosheets.Due to the sufficient sites for Co^(2+)riveting,the high loading of magnetic carbon nanotubes(CoNC)and porous carbon spheres formed high-density interfaces,enhancing the interfacial polarization.Furthermore,high-density CoNC were grown in situ on the hollow porous carbon(HPC)microsphere,forming a highly dispersed 3D magnetic network that inhibited the aggregation of magnetic nanoparticles and enhanced magnetic coupling.Therefore,the asprepared CoNC/HPC microspheres exhibited excellent microwave absorption(MA)performance,with a minimum reflection loss of-33.2 dB and an effective bandwidth of 5.5 GHz at a thickness of only 1.8 mm.The interfacial polarization mechanism for enhanced MA performance was demonstrated by electron holography and density functional theory calculations.Magnetic holography and micromagnetic simulations also revealed magnetic confinement and coupling mechanism.This work provides a new approach for designing electromagnetic absorbers with optimized impedance matching and loss capability.展开更多
文摘Dear Editor, Nanosized particulate systems combining better cancer diagnosis with therapeutic effect are being designed based on the merging of nanotechnology with cellular and molecular techniques. The surface of these nanoscale carriers is often functionalized with biological molecules for stabilization and targeted delivery. The combinations of nano-core and associated functional molecules can cross the cell membrane [1], and the surface of nanomaterials （including coating and associated functional molecules） plays a critical role in determining the outcome of their interactions with cells [2, 3]. Studying the potential effects of nanomaterials in biological systems often requires the administration of nanoparticles into a cell culture system or into living organisms in vivo. It should be noted, however, that under such conditions nanopaticles are known to adsorb proteins from the biological system,
基金the support of the State Key Laboratory of Environmental Criteria and Risk Assessment(SKLECRA2013FP12)the Shandong Province Key Research and Development Program(2016GSF115040)。
文摘In this work,Fe/Ni nanoparticles were produced through Fe(II)and Ni(II)reduction by NaBH4 and they were stabilized by a kind of prepared granular adsorbent(Fe/Ni@PGA).Fe/Ni@PGA as an environment-friendly activator was used to activate persulfate(PS)for the removal of ciprofloxacin from aqueous solution.Fe/Ni@PGA was systematically characterized via Brunauer-Emmett-Teller(BET)method,X-ray diffraction(XRD),scanning electron microscopy(SEM),and Fourier transform infrared spectroscopy(FTIR).The effects of PS concentration,initial solution pH,Fe/Ni@PGA dosage,initial ciprofloxacin concentration,reaction temperature,anions,and natural organic matters on the removal of ciprofloxacin by Fe/Ni@PGA/PS were analyzed.The removal efficiency of ciprofloxacin by Fe/Ni@PGA/PS was 93.24%under an initial pH of 3.0,PS concentration of 10 mM,Fe/Ni@PGA dosage of 0.1 g,and reaction temperature of 30℃.Fe/Ni@PGA could still exhibit high catalytic activity after nine cycles of regeneration.The removal mechanisms for ciprofloxacin by the Fe/Ni@PGA/PS system were proposed.In summary,the Fe/Ni@PGA/PS system could be applied as a promising technology for ciprofloxacin removal.
文摘Due to high efficiency,high controllability,high integration,lightweight,and other advantages,electric vehicle with hub motor driving technology has become an emerging trend of chassis technology.This paper concludes the current state⁃of⁃the⁃art of hub motor drive technologies.Firstly,it summarizes recent hub motor drive products and makes suggestions for hub motor drive schemes in different application scenarios.Then research on hub motor drive key technologies such as integrated design,thermal optimization,lightweight,and intensity optimization is investigated.Considering the high response accuracy and zero delay characteristic of hub motor driving system combined with advanced distributed dynamics control technology that can further improve vehicle performance,this paper also analyzes existing chassis dynamics control technologies of hub motor driving system.Considering the development trend of vehicle electrification,intelligentization,network connection,and current research,this paper makes some forecasts for hub motor drive technologies development in the conclusion.
基金Financial support from National Natural Science Foundation of China(nos 11205136 and 11505145)the Research Fund for Doctoral Program of Southwest University of Science and Technology(no.l4zx7166)
文摘In order to understand the dnve-in target in a D-D type neutron generator,it is essential to study the mechanism of the interaction between hydrogen ion beams and the hydrogenabsorbing metal film.The present research concerns the nucleation of hydride within zirconium film implanted with hydrogen ions.Doses of 30 keV hydrogen ions ranging from 4.30×10^（17） to1.43×10^（18） ions cm^（-2） were loaded into the zirconium film through the ion beam implantation technique.Features of the surface morphology and transformation of phase structures were investigated with scanning electron microscopy,atomic force microscopy and x-ray diffraction.Confirmation of the formation of 5 phase zirconium hydride in the implanted samples was first made by x-ray diffraction,and the different stages in the gradual nucleation and growth of zirconium hydride were then observed by atomic force microscope and scanning electron microscopy.
基金Supported by Anhui Provincial Education Department Project(KJ2019A0213)National Natural Science Foundation of China(31501245)Undergraduate Innovation and Enterpreneurship Training Program of Anhui Province(S202010364185,XJDC2020541,202110364788)。
文摘[Objectives]This study was conducted to construct a pColdI-HSP70 recombinant prokaryotic expression vector.[Methods]With rice‘N22’as the test variety,hydroponic experiments were set up for rice seedlings with normal growth(CK),high temperature treatment(H),drought treatment(D)and drought-high temperature cross treatment(DH).The recombinant prokaryotic expression vector was constructed by the method of prokaryotic expression,and its induction expression time,IPTG concentration and temperature were optimized.[Results]The pColdI-HSP70 expression vector was successfully constructed,and the fusion protein was highly expressed in host strain BL21,and the expressed proteins were all in a soluble form.By optimizing the induction expression conditions,it was found that the optimal expression conditions were the IPTG concentration of 0.5 mmol/L and induction at 20℃for 36 h.The expression analysis of the rice HSP70 gene under different stress treatments was carried out by qRT-PCR technology,and it was found that H,D and DH stresses all could induce its expression,and its expression levels were 4.65,1.40 and 17.66 times higher than that of the CK group,respectively.[Conclusions]This study lays a solid foundation for the isolation,purification and functional study of rice HSP70 proteins.
文摘At present, there are significant regional differences in average life expectancy among countries in the world. Not only is there a great disparity in average life expectancy, but also the gender difference is positive and negative, and is distributed in a bipolar distribution of “long life in rich countries and short life in poor countries”. This paper analyzes the factors affecting the life grade by using the ordered multivariate discrete selection model and combined with the average life expectancy data of countries all over the world in 2017. The test results show that: 1) The growth of per capita GDP, elderly dependency ratio and the proportion of people using at least basic drinking water services can effectively improve the level of life expectancy;2) The birth rate has an inhibitory effect on the average life expectancy;3) Through model comparison, probit model is more suitable for the analysis of this kind of problems than logit model, and the properties of the obtained model are better.
基金This work was supported by the Ministry of Science and Technology of China(No.2018YFA0209102)the National Natural Science Foundation of China(Nos.11727807,51725101,51672050 and 61790581)the Science and Technology Commission of Shanghai Municipality(No.l6DZ2260600).
文摘Carbon-sulfur composites have draw n in creasing interest in various fields including electrocatalysis because of their unique structures.However,carb on-sulfur composite with tiny sulfur nano crystals has still received little attention.Herein,hollow porous carb on sphere-sulfur composite(HPCS-S)which possesses excellent electrochemical performance towards H2O2 has been prepared for the first time via a simple silica template method.The 2-5 nm sulfur nan ocrystals being restricted in the cha nnel of the hollow porous carb on spheres are un der a strong compressive stress,which was further con firmed by high-resoluti on tran smissi on electr on microscopy(HRTEM)and GPA.The HPCS-S nano crystals show better con ductivity tha n amorphous sulfur clusters because of the reducti on of the steric hindrance which efficie ntly promotes the electron transportation.Consequently,the higher activity and selectivity towards the 2e^oxygen reduction reaction(ORR)to H2O2 in alkaline solution was obtained.The H2O2 selectivity rises from 20%to over 70%after the sulfur addition and the H2O2 production rate achieves 183.99 mmol-gcataiyst-1 with the Faradaic efficiency of 70%.Furthermore,performance enhancement mechanism was also investigated using the den sity functional theory(DFT)calculatio ns.After the in troduci ng of sulfur nano crystals,the appeara nee of S-S bond greatly decreases the overpotential compared with S-doping,which results in significant enhancement of the electrocatalytic property.Consequently,the HPCS-S can be an efficient H2O2 production electrocatalyst in alkaline solution.
基金This work was supported by the National Basic Research Program of China(No.2018YFA209102)the National Natural Science Foundation of China(Nos.11727807,51725101,51672050,and 61790581).
文摘Developing efficient and low-cost electrocatalysts for oxygen evolution reaction(OER)with high electrochemical activity and durability for diverse renewable and sustainable energy technologies remains challenging.Herein,an ultrasonic-assisted and coordination modulation strategy is developed to construct sandwich-like metal-organic framework(MOF)derived hydroxide nanosheet(NS)arrays/graphene oxide(GO)composite via one-step self-transformation route.Inducing from unsteady state,the dodecahedral ZIF-67 with Co^2+in tetrahedral coordination auto-converts into defect-rich ultrathin layered hydroxides with the interlayered ion NO3-.The self-transforming a-Co(OH)2/GO nanosheet arrays from ZIF-67(Co(OH)2-GNS)change the coordination mode of Co^2+and bring about the exposure of more metal active sites,thereby enhancing the spatial utilization ratio within the framework.As monometal-based electrocatalyst,the optimized Co(OH)2-GNS exhibits remarkable OER catalytic performance evidenced by a low overpotential of 259 mV to achieve a current density of 10 mA·cm-2 in alkaline medium,even exceeding commercial RuO2.During the oxygen evolution process,electron migration can be accelerated by the interfacial/in-plane charge polarization and local electric field,corroborated by the off-axis electron holography.Density functional theory(DFT)calculations further studied the collaboration between ultrathin Co(OH)2 NS and GO,which leads to lower energy barriers of intermediate products and greatly promotes electrocatalytic property.
基金This work was supported by the Ministry of Science and Technology of China(973 Project)(No.2018YFA0209102)the National Natural Science Foundation of China(Nos.11727807,51725101,51672050,and 61790581)。
文摘Design and fabrication of cost-effective transition metal and their oxides-based nanocomposites are of paramount significance for metal-air batteries and water-splitting.However,the traditional optimized designs for nanostructure are complicated,low-efficient and underperform for wide-scale applications.Herein,a novel hierarchical framework of hollow Ni/NiFe2O4-CNTs compositemicrosphere forcibly-assembled by zero-dimensional(OD)Ni/NiFo204 nanoparticle(<16 nm)and one-dimensional(1D)self-supporting CNTs was fabricated successfully.Benefitted from the unique nanostructure,such monohybrids can achieve remarkable oxygen evolution reaction(OER)performance in alkaline media with a low overpotential and superior durability,which exceeds most of the commercial catalysts based on IrO/RuO2 or other non-noble metal nanomaterials.The enhanced OER performance of Ni/NiFe2OA-CNTs composite is mainly ascribed to the increased catalytic activity and the optimized conductivity induced by the effects of strong hierarchical coupling and charge transfers between CNTs and Ni/NiFe204 nanoparticles.These effects are greatly boosted by the polarized heterojunction interfaces confirmed by electron holography.The density functional theory(DFT)calculation indicates the epitaxial Ni further enriches the intrinsic electrons contents of NiFe204 and thus accelerates absorption/desorption kinetics of OER intermediates.This work hereby paves a facile route to construct the hollow composite microsphere with excellent OER electrocatalytic activity based on non-noble metal oxide/CNTs.
文摘Manganese selenide （MnSe） possesses unique magnetic properties as an important magnetic semiconductor, but the synthesis and properties of MnSe nanocrystals are less developed compared to other semiconductor nanocrystals because of the inability to obtain high-quality MnSe, especially in the metastable wurtzite structure. Here, we have successfully fabricated wurtzite MnSe nanocrystals via a colloidal approach which affords uniform crystal sizes and tailored shapes. The selective binding strength of the amine surfactant is the determining factor in shape-control and shape-evolution. Bullet-shapes could be transformed into shuttle-shapes if part of the oleylamine in the reaction solution was replaced by trioctylamine, and tetrapod-shaped nanocrystals could be formed in trioctylamine systems. The three-dimensional （3D） structure of the bullet-shaped nanorods has been demonstrated by the advanced transmission electron microscope （TEM） 3D-tomography technology. High-resolution TEM （HRTEM） and electron energy-loss spectroscopy （EELS） show that planar-defect structures such as stacking faults and twinning along the [001] direction arise during the growth of bullet-shapes. On the basis of careful HRTEM observations, we propose a ＂quadra-twin core＂ growth mechanism for the formation of wurtzite MnSe nanotetrapods. Furthermore, the wurtzite MnSe nanocrystals show low- temperature surface spin-glass behavior due to their noncompensated surface spins and the blocking temperatures increase from 8.4 K to 18.5 K with increasing surface area/volume ratio of the nanocrystals. Our results provide a systematic study of wurtzite MnSe nanocrystals.
基金supported by the National Natural Science Foundation of China(Nos.52231007,51725101,11727807)the Ministry of Science and Technology of China(Nos.2021YFA1200600 and 2018YFA0209102).
文摘The hollow porous structure with exceptional interfacial effect and customizable internal environment shows significant potential for application as electromagnetic shielding and absorption materials.However,designing hollow porous electromagnetic absorbers with both desirable impedance matching and high loss capability remains a challenge.Herein,3D hollow porous electromagnetic microspheres were constructed by assembling 0D Co magnetic nanoparticles,1D carbon nanotubes,and 2D carbon nanosheets.Due to the sufficient sites for Co^(2+)riveting,the high loading of magnetic carbon nanotubes(CoNC)and porous carbon spheres formed high-density interfaces,enhancing the interfacial polarization.Furthermore,high-density CoNC were grown in situ on the hollow porous carbon(HPC)microsphere,forming a highly dispersed 3D magnetic network that inhibited the aggregation of magnetic nanoparticles and enhanced magnetic coupling.Therefore,the asprepared CoNC/HPC microspheres exhibited excellent microwave absorption(MA)performance,with a minimum reflection loss of-33.2 dB and an effective bandwidth of 5.5 GHz at a thickness of only 1.8 mm.The interfacial polarization mechanism for enhanced MA performance was demonstrated by electron holography and density functional theory calculations.Magnetic holography and micromagnetic simulations also revealed magnetic confinement and coupling mechanism.This work provides a new approach for designing electromagnetic absorbers with optimized impedance matching and loss capability.
