The activation of iron oxide Fischer–Tropsch Synthesis(FTS) catalysts was investigated during pretreatment: reduction in hydrogen followed by carburization in either CO or syngas mixture, or simultaneously reduction ...The activation of iron oxide Fischer–Tropsch Synthesis(FTS) catalysts was investigated during pretreatment: reduction in hydrogen followed by carburization in either CO or syngas mixture, or simultaneously reduction and carburization in syngas. A combination of different complementary in situ techniques was used to gain insight into the behavior of Fe-based FTS catalysts during activation. In situ XRD was used to identify the crystalline structures present during both reduction in hydrogen and carburization. An increase in reduction rate was established when increasing the temperature. A complete reduction was demonstrated in the ETEM and a grain size dependency was proven, i.e. bigger grains need higher temperature in order to reduce. XPS and XAS both indicate the formation of a small amount of carbonaceous species at the surface of the bulk metallic iron during carburization.展开更多
Here,a novel fabrication method for making free-standing 3D hierarchical porous carbon aerogels from molecularly engineered biomass-derived hydrogels is presented.In situ formed flower-like CaCO_(3)molecularly embedde...Here,a novel fabrication method for making free-standing 3D hierarchical porous carbon aerogels from molecularly engineered biomass-derived hydrogels is presented.In situ formed flower-like CaCO_(3)molecularly embedded within the hydrogel network regulated the pore structure during in situ mineralization assisted one-step activation graphitization(iMAG),while the intrinsic structural integrity of the carbon aerogels was maintained.The homogenously distributed minerals simultaneously acted as a hard template,activating agent,and graphitization catalyst.The decomposition of the homogenously distributed CaCO_(3)during iMAG followed by the etching of residual CaO through a mild acid washing endowed a robust carbon aerogel with high porosity and excellent electrochemical performance.At 0.5 mA cm^(-2),the gravimetric capacitance increased from 0.01 F g^(-1)without mineralization to 322 F g^(-1)with iMAG,which exceeds values reported for any other free-standing or powder-based biomass-derived carbon electrodes.An outstanding cycling stability of~104%after 1000 cycles in 1 M HClO4 was demonstrated.The assembled symmetric supercapacitor device delivered a high specific capacitance of 376 F g^(-1)and a high energy density of 26 W h kg^(-1)at a power density of 4000 W kg^(-1),with excellent cycling performance(98.5%retention after 2000 cycles).In combination with the proposed 3D printed mold-assisted solution casting(3DMASC),iMAG allows for the generation of free-standing carbon aerogel architectures with arbitrary shapes.Furthermore,the novel method introduces flexibility in constructing free-standing carbon aerogels from any ionically cross-linkable biopolymer while maintaining the ability to tailor the design,dimensions,and pore size distribution for specific energy storage applications.展开更多
Particle size and shape of cells are essential determining the outcome of drug delivery of nano carrier for medical applications.In this study,different size silver nanoparticles were controllably synthesized to treat...Particle size and shape of cells are essential determining the outcome of drug delivery of nano carrier for medical applications.In this study,different size silver nanoparticles were controllably synthesized to treat two shapes of cells.Silver nanoparticles(AgNPs)were synthesized via chemical reduction using NaBH4 and modified with polyvinylpyrrolidone(PVP)and bovine serum albumin(BSA)or encapsulated in liposomes to enhance cellular uptake.Different nanoparticle sizes were obtained as follows:uncapped AgNPs(30 nm),PVP–AgNPs(34.7 nm),BSA–AgNPs(113.9–145.2 nm),and liposome-encapsulated AgNPs(70.9–142.0 nm).Liposomes with a 5:3 molar ratio of dipalmitoylphosphatidylcholine(DPPC)-to-cholesterol formed stable vesicles,each encapsulating up to 66 AgNPs at a concentration of 2 mmol/L.Cytotoxicity assays revealed that uncapped 2 mM AgNPs exhibited strong toxicity toward both Caco-2 and U251 cells(IC_(50):13.52μmol/L at 24 h).Liposomal AgNPs displayed concentration-dependent effects,with 1 mM AgNPs–liposomes exhibiting the highest toxicity toward Caco-2 cells(IC_(50):0.5μmol/L at 24 h),but significantly lower toxicity toward U251 cells(IC_(50):134.3μmol/L at 24 h).The formulation exhibiting the highest toxicity at 48 h was 2 mmol/L AgNPs–liposomes against Caco-2 cells(IC_(50):4.6μmol/L).In contrast,BSA and PVP coatings significantly reduced toxicity,with IC_(50) of 2.2μmol/L for 50 mmol/L BSA–AgNPs and 14.9μmol/L for 50 mmol/L PVP–AgNPs in Caco-2 cells.Liposome-encapsulated AgNPs showed enhanced toxicity against square-shaped Caco-2 cells compared to fibroblast-like U251 cells(p<0.05),highlighting their potential for targeted cancer therapy.The findings of this study demonstrate that surface modifications and encapsulation strategies critically influence the biological effects of AgNPs in liposomes,providing a promising approach for enhanced anticancer activity.展开更多
Thermal nanoimprinting is a fast and versatile method for transferring the anti-reflective properties of subwavelength nanostructures onto the surface of highly reflective substrates, such as chalcogenide glass optica...Thermal nanoimprinting is a fast and versatile method for transferring the anti-reflective properties of subwavelength nanostructures onto the surface of highly reflective substrates, such as chalcogenide glass optical fiber end faces. In this paper, the technique is explored experimentally on a range of different types of commercial and custom-drawn optical fibers to evaluate the influence of geometric design, core/cladding material, and thermo-mechanical properties. Up to32.4% increased transmission and 88.3% total transmission are demonstrated in the 2–4.3 μm band using a mid-infrared(IR) supercontinuum laser.展开更多
Periodic noble metal nanoparticles offer a wide spectrum of applications including chemical and biological sensors,optical devices,and model catalysts due to their extraordinary properties.For sensing purposes and cat...Periodic noble metal nanoparticles offer a wide spectrum of applications including chemical and biological sensors,optical devices,and model catalysts due to their extraordinary properties.For sensing purposes and catalytic studies,substrates made of glass or fused-silica are normally required as supports,without the use of metallic adhesion layers.However,precise patterning of such uniform arrays of silica-supported noble metal nanoparticles,especially at sub-100 nm in diameter,is challenging without adhesion layers.In this paper,we report a robust method to large-scale fabricate highly ordered sub-20 nm noble metal nanoparticles,i.e.,gold and platinum,supported on silica substrates without adhesion layers,combining displacement Talbot lithography(DTL)with dry-etching techniques.Periodic photoresist nanocolumns at diameters of~110 nm are patterned on metal-coated oxidized silicon wafers using DTL,and subsequently transferred at a 1:1 ratio into anti-reflection layer coating(BARC)nanocolumns with the formation of nano-sharp tips,using nitrogen plasma etching.These BARC nanocolumns are then used as a mask for etching the deposited metal layer using inclined argon ion-beam etching.We find that increasing the etching time results in coneshaped silica features with metal nanoparticles on the tips at diameters ranging from 100 nm to sub-30 nm,over large areas of 3×3 cm^(2).Moreover,subsequent annealing these sub-30 nm metal nanoparticle arrays at high-temperature results in sub-20 nm metal nanoparticle arrays with~10^(10) uniform particles.展开更多
The particles of heterogeneous catalysts differ greatly in size,morphology,and most importantly,in activity.Studying these catalyst particles in batch typically results in ensemble averages,without any information at ...The particles of heterogeneous catalysts differ greatly in size,morphology,and most importantly,in activity.Studying these catalyst particles in batch typically results in ensemble averages,without any information at the level of individual catalyst particles.To date,the study of individual catalyst particles has been rewarding but is stll rather slow and often cumbersomel.Furthermore,these valuable in-depth studies at the single particle level lack statistical relevance.Here,we report the development of a droplet microreactor for high-throughput fluorescence-based measurements of the acidities of individual particles in fluid catalytic cracking(FCC)equilibrium catalysts(ECAT).This method combines systematic screening of single catalyst particles with statistical relevance.An oligomerization reaction of 4-methoxystyrene,catalyzed by the Bronsted acid sites inside the zeolite domains of the ECAT particles,Was performed on-chip at 95 ℃.The fluorescence signal generated by the reaction products inside the ECAT particles was detected near the outlet of the microreactor.The high-throughput acidity screening platform was capable of detecting~1000 catalyst particles at a rate of 1 catalyst particle every 2.4 s.The number of detected catalyst particles was representative of the overall catalyst particle population with a confidence level of 95%.The measured fluorescence intensities showed a clear acidity distribution among the catalyst particles,with the majority(96.1%)showing acidity levels belonging to old,deactivated catalyst particles and a minority(3.9%)exhibiting high acidity levels.The latter are potentially of high interest,as they reveal interesting new physicochemical properties indicating why the particles were still highly acidic and reactive.展开更多
We present a low-cost and easy-to-implement technique to fabricate large-area WS_(2) photodetector devices onto transparent and flexible polycarbonate substrates.The method relies on the deposition of large-area(in th...We present a low-cost and easy-to-implement technique to fabricate large-area WS_(2) photodetector devices onto transparent and flexible polycarbonate substrates.The method relies on the deposition of large-area(in the cm scale)thin films(~30 nm thick)of WS_(2) by a recently introduced abrasion-induced method.Interdigitated electrical contacts are then deposited by thermal evaporation through a shadow mask.The photodetectors present well-balanced performances with an good trade-off between responsivity(up to 144 mA/W at a source-drain voltage of 10 V and illumination power of 1μW)and response time(down to~70µs)and a detectivity value of 10^(8) Jones.We found that the devices perform very reversibly upon several illumination and straining cycles and we found a moderate device-to-device variation.展开更多
Lanthanides(Ln^(3+))doped luminescent materials play critical roles in lighting and display techniques.While increasing experimental and theoretical research have been carried out on aluminate-based phosphors for whit...Lanthanides(Ln^(3+))doped luminescent materials play critical roles in lighting and display techniques.While increasing experimental and theoretical research have been carried out on aluminate-based phosphors for white light-emitting diodes(WLEDs)over the past decades,most investigation was mainly focused on their luminescent properties;therefore,the local structure of the light emission center remains unclear.Especially,doping-induced local composition and structure modification around the luminescent centers have yet to be unveiled.In this study,we use advanced electron microscopy techniques including electron diffraction(ED),high-resolution transmission electron microscopy(HRTEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),in combination with energy dispersive X-ray spectroscopy(EDX)and electron energy loss spectroscopy(EELS),to reveal atomically resolved crystalline and chemical structure of Ce^(3+)doped CaYAlO4.The microscopic results prove substantial microstructural and compositional inhomogeneities in Ce^(3+)doped CaYAlO_(4),especially the appearance of Ce dopant clustering and Ce^(3+)/Ce^(4+)valence variation.Our research provides a new understanding the structure of Ln^(3+)doped luminescent materials and will facilitate the materials design for next-generation WLEDs luminescent materials.展开更多
Advanced electron microscopy techniques,including scanning electron microscopes(SEM),scanning transmission electron microscopes(STEM),and transmission electron microscopes(TEM),have revolutionized imaging capabilities...Advanced electron microscopy techniques,including scanning electron microscopes(SEM),scanning transmission electron microscopes(STEM),and transmission electron microscopes(TEM),have revolutionized imaging capabilities.However,achieving high-quality experimental images remains a challenge due to various distortions stemming from the instrumentation and external factors.These distortions,introduced at different stages of imaging,hinder the extraction of reliable quantitative insights.In this paper,we will discuss the main sources of distortion in TEM and S(T)EM images,develop models to describe them,and propose a method to correct these distortions using a convolutional neural network.We validate the effectiveness of our method on a range of simulated and experimental images,demonstrating its ability to significantly enhance the signal-to-noise ratio.This improvement leads to a more reliable extraction of quantitative structural information from the images.In summary,our findings offer a robust framework to enhance the quality of electron microscopy images,which in turn supports progress in structural analysis and quantification in materials science and biology.展开更多
Thermal analysis is essential for the characterization of polymers and drugs.However,the currently established methods require a large amount of sample.Here,we present pyrolytic carbon resonators as promising tools fo...Thermal analysis is essential for the characterization of polymers and drugs.However,the currently established methods require a large amount of sample.Here,we present pyrolytic carbon resonators as promising tools for micromechanical thermal analysis(MTA)of nanograms of polymers.Doubly clamped pre-stressed beams with a resonance frequency of 233±4 kHz and a quality factor(Q factor)of 800±200 were fabricated.Optimization of the electrical conductivity of the pyrolytic carbon allowed us to explore resistive heating for integrated temperature control.MTA was achieved by monitoring the resonance frequency and quality factor of the carbon resonators with and without a deposited sample as a function of temperature.To prove the potential of pyrolytic carbon resonators as thermal analysis tools,the glass transition temperature(T_(g))of semicrystalline poly(L-lactic acid)(PLLA)and the melting temperature(T_(m))of poly(caprolactone)(PCL)were determined.The results show that the T_(g) of PLLA and T_(m) of PCL are 61.0±0.8℃ and 60.0±1.0℃,respectively,which are in excellent agreement with the values measured by differential scanning calorimetry(DSC).展开更多
Ferroelectric barium titanate nanoparticles(BTO NPs)may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors.While increasing experimental and theoretical understandi...Ferroelectric barium titanate nanoparticles(BTO NPs)may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors.While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade,the majority of the investigation was carried out in thin-film materials;therefore,the doping effect on nanoparticles remains unclear.Especially,doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled.In this work,we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),integrated differential phase contrast(iDPC)-STEM,and energy dispersive X-ray spectroscopy(EDX)mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles.Powder X-ray diffraction(PXRD)results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase,but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles.Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.展开更多
We introduce a Bayesian genetic algorithm for reconstructing atomic models of monotype crystalline nanoparticles from a single projection using Z-contrast imaging.The number of atoms in a projected atomic column obtai...We introduce a Bayesian genetic algorithm for reconstructing atomic models of monotype crystalline nanoparticles from a single projection using Z-contrast imaging.The number of atoms in a projected atomic column obtained from annular dark field scanning transmission electron microscopy images serves as an input for the initial three-dimensional model.The algorithm minimizes the energy of the structure while utilizing a priori information about the finite precision of the atom-counting results and neighbor-mass relations.The results show promising prospects for obtaining reliable reconstructions of beam-sensitive nanoparticles during dynamical processes from images acquired with sufficiently low incident electron doses.展开更多
The current progress of system miniaturization relies extensively on the development of 3D machining techniques to increase the areal structure density.In this work,a wafer-scale out-of-plane 3D silicon(Si)shaping tec...The current progress of system miniaturization relies extensively on the development of 3D machining techniques to increase the areal structure density.In this work,a wafer-scale out-of-plane 3D silicon(Si)shaping technology is reported,which combines a multistep plasma etching process with corner lithography.The multistep plasma etching procedure results in high aspect ratio structures with stacked semicircles etched deep into the sidewall and thereby introduces corners with a proper geometry for the subsequent corner lithography.Due to the geometrical contrast between the gaps and sidewall,residues are left only inside the gaps and form an inversion mask inside the semicircles.Using this mask,octahedra and donuts can be etched in a repeated manner into Si over the full wafer area,which demonstrates the potential of this technology for constructing high-density 3D structures with good dimensional control in the bulk of Si wafers.展开更多
基金supported by the “Villum Center for the Science of Sustainable Fuels and Chemicals” (V-Sustain, grant number 9455) research initiative funded by the VILLUM FONDEN。
文摘The activation of iron oxide Fischer–Tropsch Synthesis(FTS) catalysts was investigated during pretreatment: reduction in hydrogen followed by carburization in either CO or syngas mixture, or simultaneously reduction and carburization in syngas. A combination of different complementary in situ techniques was used to gain insight into the behavior of Fe-based FTS catalysts during activation. In situ XRD was used to identify the crystalline structures present during both reduction in hydrogen and carburization. An increase in reduction rate was established when increasing the temperature. A complete reduction was demonstrated in the ETEM and a grain size dependency was proven, i.e. bigger grains need higher temperature in order to reduce. XPS and XAS both indicate the formation of a small amount of carbonaceous species at the surface of the bulk metallic iron during carburization.
基金financially supported by the European Research Council under the Horizon 2020 framework programme(Grant No.772370-PHOENEEX)
文摘Here,a novel fabrication method for making free-standing 3D hierarchical porous carbon aerogels from molecularly engineered biomass-derived hydrogels is presented.In situ formed flower-like CaCO_(3)molecularly embedded within the hydrogel network regulated the pore structure during in situ mineralization assisted one-step activation graphitization(iMAG),while the intrinsic structural integrity of the carbon aerogels was maintained.The homogenously distributed minerals simultaneously acted as a hard template,activating agent,and graphitization catalyst.The decomposition of the homogenously distributed CaCO_(3)during iMAG followed by the etching of residual CaO through a mild acid washing endowed a robust carbon aerogel with high porosity and excellent electrochemical performance.At 0.5 mA cm^(-2),the gravimetric capacitance increased from 0.01 F g^(-1)without mineralization to 322 F g^(-1)with iMAG,which exceeds values reported for any other free-standing or powder-based biomass-derived carbon electrodes.An outstanding cycling stability of~104%after 1000 cycles in 1 M HClO4 was demonstrated.The assembled symmetric supercapacitor device delivered a high specific capacitance of 376 F g^(-1)and a high energy density of 26 W h kg^(-1)at a power density of 4000 W kg^(-1),with excellent cycling performance(98.5%retention after 2000 cycles).In combination with the proposed 3D printed mold-assisted solution casting(3DMASC),iMAG allows for the generation of free-standing carbon aerogel architectures with arbitrary shapes.Furthermore,the novel method introduces flexibility in constructing free-standing carbon aerogels from any ionically cross-linkable biopolymer while maintaining the ability to tailor the design,dimensions,and pore size distribution for specific energy storage applications.
文摘Particle size and shape of cells are essential determining the outcome of drug delivery of nano carrier for medical applications.In this study,different size silver nanoparticles were controllably synthesized to treat two shapes of cells.Silver nanoparticles(AgNPs)were synthesized via chemical reduction using NaBH4 and modified with polyvinylpyrrolidone(PVP)and bovine serum albumin(BSA)or encapsulated in liposomes to enhance cellular uptake.Different nanoparticle sizes were obtained as follows:uncapped AgNPs(30 nm),PVP–AgNPs(34.7 nm),BSA–AgNPs(113.9–145.2 nm),and liposome-encapsulated AgNPs(70.9–142.0 nm).Liposomes with a 5:3 molar ratio of dipalmitoylphosphatidylcholine(DPPC)-to-cholesterol formed stable vesicles,each encapsulating up to 66 AgNPs at a concentration of 2 mmol/L.Cytotoxicity assays revealed that uncapped 2 mM AgNPs exhibited strong toxicity toward both Caco-2 and U251 cells(IC_(50):13.52μmol/L at 24 h).Liposomal AgNPs displayed concentration-dependent effects,with 1 mM AgNPs–liposomes exhibiting the highest toxicity toward Caco-2 cells(IC_(50):0.5μmol/L at 24 h),but significantly lower toxicity toward U251 cells(IC_(50):134.3μmol/L at 24 h).The formulation exhibiting the highest toxicity at 48 h was 2 mmol/L AgNPs–liposomes against Caco-2 cells(IC_(50):4.6μmol/L).In contrast,BSA and PVP coatings significantly reduced toxicity,with IC_(50) of 2.2μmol/L for 50 mmol/L BSA–AgNPs and 14.9μmol/L for 50 mmol/L PVP–AgNPs in Caco-2 cells.Liposome-encapsulated AgNPs showed enhanced toxicity against square-shaped Caco-2 cells compared to fibroblast-like U251 cells(p<0.05),highlighting their potential for targeted cancer therapy.The findings of this study demonstrate that surface modifications and encapsulation strategies critically influence the biological effects of AgNPs in liposomes,providing a promising approach for enhanced anticancer activity.
基金financially supported by the Research Council of Norway via the PETROMAKS2 Project Durable Arctic Icephobic Materials(255507)the NANO2021 Project Dual-Functional Anti-Gas Hydrate Surfaces(302348)+1 种基金the Norwegian Micro-and Nano-Fabrication Facility,Nor Fab(245963)the support of the National Natural Science Foundation of China(12002350)。
基金supported by the European Commission (Nos. 317803, 722380, and 732968)the Innovation Fund Denmark (No. 4107-00011A)+2 种基金the Danish Maritime Fund (No. 2019-137)the Lundbeck Foundation (No. R276-2018869)the Independent Research Fund Denmark (No. 8022-00091B)。
文摘Thermal nanoimprinting is a fast and versatile method for transferring the anti-reflective properties of subwavelength nanostructures onto the surface of highly reflective substrates, such as chalcogenide glass optical fiber end faces. In this paper, the technique is explored experimentally on a range of different types of commercial and custom-drawn optical fibers to evaluate the influence of geometric design, core/cladding material, and thermo-mechanical properties. Up to32.4% increased transmission and 88.3% total transmission are demonstrated in the 2–4.3 μm band using a mid-infrared(IR) supercontinuum laser.
基金This work was supported by the Netherlands Center for Multiscale Catalytic Energy Conversion(MCEC)。
文摘Periodic noble metal nanoparticles offer a wide spectrum of applications including chemical and biological sensors,optical devices,and model catalysts due to their extraordinary properties.For sensing purposes and catalytic studies,substrates made of glass or fused-silica are normally required as supports,without the use of metallic adhesion layers.However,precise patterning of such uniform arrays of silica-supported noble metal nanoparticles,especially at sub-100 nm in diameter,is challenging without adhesion layers.In this paper,we report a robust method to large-scale fabricate highly ordered sub-20 nm noble metal nanoparticles,i.e.,gold and platinum,supported on silica substrates without adhesion layers,combining displacement Talbot lithography(DTL)with dry-etching techniques.Periodic photoresist nanocolumns at diameters of~110 nm are patterned on metal-coated oxidized silicon wafers using DTL,and subsequently transferred at a 1:1 ratio into anti-reflection layer coating(BARC)nanocolumns with the formation of nano-sharp tips,using nitrogen plasma etching.These BARC nanocolumns are then used as a mask for etching the deposited metal layer using inclined argon ion-beam etching.We find that increasing the etching time results in coneshaped silica features with metal nanoparticles on the tips at diameters ranging from 100 nm to sub-30 nm,over large areas of 3×3 cm^(2).Moreover,subsequent annealing these sub-30 nm metal nanoparticle arrays at high-temperature results in sub-20 nm metal nanoparticle arrays with~10^(10) uniform particles.
基金supported by the Netherlands Center for Multiscale Catalytic Energy Conversion(MCEC),an NWO gravitation program funded by the Ministry of Education,Culture and Science of the government of the Netherlands.The authors would like to acknowledge Jan van Nieuwkasteele(University of Twente)for his invaluable help in setting up the Hamamatsu camera and attached computer,which enabled fast data processing for fluorescencedetection.
文摘The particles of heterogeneous catalysts differ greatly in size,morphology,and most importantly,in activity.Studying these catalyst particles in batch typically results in ensemble averages,without any information at the level of individual catalyst particles.To date,the study of individual catalyst particles has been rewarding but is stll rather slow and often cumbersomel.Furthermore,these valuable in-depth studies at the single particle level lack statistical relevance.Here,we report the development of a droplet microreactor for high-throughput fluorescence-based measurements of the acidities of individual particles in fluid catalytic cracking(FCC)equilibrium catalysts(ECAT).This method combines systematic screening of single catalyst particles with statistical relevance.An oligomerization reaction of 4-methoxystyrene,catalyzed by the Bronsted acid sites inside the zeolite domains of the ECAT particles,Was performed on-chip at 95 ℃.The fluorescence signal generated by the reaction products inside the ECAT particles was detected near the outlet of the microreactor.The high-throughput acidity screening platform was capable of detecting~1000 catalyst particles at a rate of 1 catalyst particle every 2.4 s.The number of detected catalyst particles was representative of the overall catalyst particle population with a confidence level of 95%.The measured fluorescence intensities showed a clear acidity distribution among the catalyst particles,with the majority(96.1%)showing acidity levels belonging to old,deactivated catalyst particles and a minority(3.9%)exhibiting high acidity levels.The latter are potentially of high interest,as they reveal interesting new physicochemical properties indicating why the particles were still highly acidic and reactive.
基金the Ministry of Science and Innovation (Spain)through the project PID2020-115566RB-I00.A.C.-G.,A.M.A.-E.A.N.extend their sincere appreciation to the Distinguished Scientist Fellowship Program (DSFP)at King Saud University for funding of this work+4 种基金support from the Spanish Ministry of Economy,Industry,and Competitiveness (MINECO)through a Juan de la Cierva-formación fellowship 2017 FJCI-2017-32919.J.Q.support from the Agencia Estatal de Investigación of Spain (Grants PID2019-106820RB,RTI2018-097180-B-100,and PGC2018-097018-BI00)the Junta de Castilla y León (Grants SA256P18 and SA121P20),including funding by ERDF/FEDER.J.Q.support from Universidad Complutense de Madrid and European Commision (MSCA COFUND UNA4CAREER grant.Project number 4129252)from MICINN (Spain)through the program Juan de la Cierva-Incorporación.
文摘We present a low-cost and easy-to-implement technique to fabricate large-area WS_(2) photodetector devices onto transparent and flexible polycarbonate substrates.The method relies on the deposition of large-area(in the cm scale)thin films(~30 nm thick)of WS_(2) by a recently introduced abrasion-induced method.Interdigitated electrical contacts are then deposited by thermal evaporation through a shadow mask.The photodetectors present well-balanced performances with an good trade-off between responsivity(up to 144 mA/W at a source-drain voltage of 10 V and illumination power of 1μW)and response time(down to~70µs)and a detectivity value of 10^(8) Jones.We found that the devices perform very reversibly upon several illumination and straining cycles and we found a moderate device-to-device variation.
基金funded by the National Natural Science Foundation of China(Nos.52002357,22105175,and 51932009)P.L.acknowledges the financial support from the Carlsberg Foundation(No.CF20-0612).
文摘Lanthanides(Ln^(3+))doped luminescent materials play critical roles in lighting and display techniques.While increasing experimental and theoretical research have been carried out on aluminate-based phosphors for white light-emitting diodes(WLEDs)over the past decades,most investigation was mainly focused on their luminescent properties;therefore,the local structure of the light emission center remains unclear.Especially,doping-induced local composition and structure modification around the luminescent centers have yet to be unveiled.In this study,we use advanced electron microscopy techniques including electron diffraction(ED),high-resolution transmission electron microscopy(HRTEM),high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),in combination with energy dispersive X-ray spectroscopy(EDX)and electron energy loss spectroscopy(EELS),to reveal atomically resolved crystalline and chemical structure of Ce^(3+)doped CaYAlO4.The microscopic results prove substantial microstructural and compositional inhomogeneities in Ce^(3+)doped CaYAlO_(4),especially the appearance of Ce dopant clustering and Ce^(3+)/Ce^(4+)valence variation.Our research provides a new understanding the structure of Ln^(3+)doped luminescent materials and will facilitate the materials design for next-generation WLEDs luminescent materials.
基金supported by the European Research Council(Grant 770887 PICOMETRICS to S.V.A.)The authors acknowledge financial support from the Research Foundation Flanders(FWO,Belgium)through project fundings(G034621N,G0A7723N and EOS 40007495)funding from the University of Antwerp Research Fund(BOF).
文摘Advanced electron microscopy techniques,including scanning electron microscopes(SEM),scanning transmission electron microscopes(STEM),and transmission electron microscopes(TEM),have revolutionized imaging capabilities.However,achieving high-quality experimental images remains a challenge due to various distortions stemming from the instrumentation and external factors.These distortions,introduced at different stages of imaging,hinder the extraction of reliable quantitative insights.In this paper,we will discuss the main sources of distortion in TEM and S(T)EM images,develop models to describe them,and propose a method to correct these distortions using a convolutional neural network.We validate the effectiveness of our method on a range of simulated and experimental images,demonstrating its ability to significantly enhance the signal-to-noise ratio.This improvement leads to a more reliable extraction of quantitative structural information from the images.In summary,our findings offer a robust framework to enhance the quality of electron microscopy images,which in turn supports progress in structural analysis and quantification in materials science and biology.
基金The research is funded by the Danish National Research Foundation(DNRF122)Villum Fonden(Grant No.9301)Center for Intelligent Drug Delivery and Sensing Using Microcontainers and Nanomechanics(IDUN)This work was performed in part at cleanroom facilities of DTU Nanolab,the National Center for Microfabrication and Nanofabrication at the Technical University of Denmark.
文摘Thermal analysis is essential for the characterization of polymers and drugs.However,the currently established methods require a large amount of sample.Here,we present pyrolytic carbon resonators as promising tools for micromechanical thermal analysis(MTA)of nanograms of polymers.Doubly clamped pre-stressed beams with a resonance frequency of 233±4 kHz and a quality factor(Q factor)of 800±200 were fabricated.Optimization of the electrical conductivity of the pyrolytic carbon allowed us to explore resistive heating for integrated temperature control.MTA was achieved by monitoring the resonance frequency and quality factor of the carbon resonators with and without a deposited sample as a function of temperature.To prove the potential of pyrolytic carbon resonators as thermal analysis tools,the glass transition temperature(T_(g))of semicrystalline poly(L-lactic acid)(PLLA)and the melting temperature(T_(m))of poly(caprolactone)(PCL)were determined.The results show that the T_(g) of PLLA and T_(m) of PCL are 61.0±0.8℃ and 60.0±1.0℃,respectively,which are in excellent agreement with the values measured by differential scanning calorimetry(DSC).
基金This work was supported by the National Natural Science Foundation of China(Nos.21625304,21872163,21991153,22072090,21991153,and 21991150)L.C.acknowledges the support from the Ministry of Science and Technology(No.2016YFA0200703)P.L.acknowledges the financial support from the Carlsberg Foundation.
文摘Ferroelectric barium titanate nanoparticles(BTO NPs)may play critical roles in miniaturized passive electronic devices such as multi-layered ceramic capacitors.While increasing experimental and theoretical understandings on the structure of BTO and doped BTO have been developed over the past decade,the majority of the investigation was carried out in thin-film materials;therefore,the doping effect on nanoparticles remains unclear.Especially,doping-induced local composition and structure fluctuation across single nanoparticles have yet to be unveiled.In this work,we use electron microscopy-based techniques including high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM),integrated differential phase contrast(iDPC)-STEM,and energy dispersive X-ray spectroscopy(EDX)mapping to reveal atomically resolved chemical and crystal structure of BTO and strontium doped BTO nanoparticles.Powder X-ray diffraction(PXRD)results indicate that the increasing strontium doping causes a structural transition from tetragonal to cubic phase,but the microscopic data validate substantial compositional and microstructural inhomogeneities in strontium doped BTO nanoparticles.Our work provides new insights into the structure of doped BTO NPs and will facilitate the materials design for next-generation high-density nano-dielectric devices.
基金This work was supported by the European Research Council(Grant 770887 PICOMETRICS to S.V.A.and Grant 823717 ESTEEM3)The authors acknowledge financial support from the Research Foundation Flanders(FWO,Belgium)through project fundings(G.0267.18N,G.0502.18N,G.0346.21N)+1 种基金a postdoctoral grant to A.D.B.L.J.acknowledges Science Foundation Ireland(SFI–grant number URF/RI/191637)the Royal Society,and the AMBER Centre.The authors acknowledge Aakash Varambhia for his assistance and expertise with the experimental recording and use of characterization facilities within the David Cockayne Centre for Electron Microscopy,Department of Materials,University of Oxford,and in particular the EPSRC(EP/K040375/1 South of England Analytical Electron Microscope).
文摘We introduce a Bayesian genetic algorithm for reconstructing atomic models of monotype crystalline nanoparticles from a single projection using Z-contrast imaging.The number of atoms in a projected atomic column obtained from annular dark field scanning transmission electron microscopy images serves as an input for the initial three-dimensional model.The algorithm minimizes the energy of the structure while utilizing a priori information about the finite precision of the atom-counting results and neighbor-mass relations.The results show promising prospects for obtaining reliable reconstructions of beam-sensitive nanoparticles during dynamical processes from images acquired with sufficiently low incident electron doses.
基金Financial support for this project was provided by the Foundation for Fundamental Research on Matter(FOM,Project 13CO12-1)which is part of The Netherlands Organization for Scientific Research(NWO).
文摘The current progress of system miniaturization relies extensively on the development of 3D machining techniques to increase the areal structure density.In this work,a wafer-scale out-of-plane 3D silicon(Si)shaping technology is reported,which combines a multistep plasma etching process with corner lithography.The multistep plasma etching procedure results in high aspect ratio structures with stacked semicircles etched deep into the sidewall and thereby introduces corners with a proper geometry for the subsequent corner lithography.Due to the geometrical contrast between the gaps and sidewall,residues are left only inside the gaps and form an inversion mask inside the semicircles.Using this mask,octahedra and donuts can be etched in a repeated manner into Si over the full wafer area,which demonstrates the potential of this technology for constructing high-density 3D structures with good dimensional control in the bulk of Si wafers.
