Ternary transition metal dichalcogenide alloys with spatially graded bandgaps are an emerging class of two-dimensional materials with unique features,which opens up new potential for device applications.Here,visible–...Ternary transition metal dichalcogenide alloys with spatially graded bandgaps are an emerging class of two-dimensional materials with unique features,which opens up new potential for device applications.Here,visible–near-infrared and self-powered phototransistors based on spatially bandgap-graded MoS2(1−x)Se2x alloys,synthesized by a simple and controllable chemical solution deposition method,are reported.The graded bandgaps,arising from the spatial grading of Se composition and thickness within a single domain,are tuned from 1.83 to 1.73 eV,leading to the formation of a homojunction with a builtin electric field.Consequently,a strong and sensitive gate-modulated photovoltaic effect is demonstrated,enabling the homojunction phototransistors at zero bias to deliver a photoresponsivity of 311 mA W−1,a specific detectivity up to^10^11 Jones,and an on/off ratio up to^10^4.Remarkably,when illuminated by the lights ranging from 405 to 808 nm,the biased devices yield a champion photoresponsivity of 191.5 A W−1,a specific detectivity up to^1012 Jones,a photoconductive gain of 10^6–10^7,and a photoresponsive time in the order of^50 ms.These results provide a simple and competitive solution to the bandgap engineering of two-dimensional materials for device applications without the need for p–n junctions.展开更多
The origin of sedimentary dolomite has become a long-standing problem in the Earth Sciences.Some carbonate minerals like ankerite have the same crystal structure as dolomite,hence their genesis may provide clues to he...The origin of sedimentary dolomite has become a long-standing problem in the Earth Sciences.Some carbonate minerals like ankerite have the same crystal structure as dolomite,hence their genesis may provide clues to help solving the dolomite problem.The purpose of this study was to probe whether microbial activity can be involved in the formation of ankerite.Bio-carbonation experiments associated with microbial iron reduction were performed in batch systems with various concentrations of Ca^(2+)(0–20 mmol/L),with a marine iron-reducing bacterium Shewanella piezotolerans WP3 as the reaction mediator,and with lactate and ferrihydrite as the respective electron donor and acceptor.Our biomineralization data showed that Ca-amendments expedited microbially-mediated ferrihydrite reduction by enhancing the adhesion between WP3 cells and ferrihydrite particles.After bioreduction,siderite occurred as the principal secondary mineral in the Ca-free systems.Instead,Ca-Fe carbonates were formed when Ca^(2+)ions were present.The CaCO_(3) content of microbially-induced Ca-Fe carbonates was positively correlated with the initial Ca2+concentration.The Ca-Fe carbonate phase produced in the 20 mmol/L Ca-amended biosystems had a chemical formula of Ca_(0.8)Fe_(1.2)(CO_(3))_(2),which is close to the theoretical composition of ankerite.This ankeritelike phase was nanometric in size and spherical,Ca-Fe disordered,and structurally defective.Our simulated diagenesis experiments further demonstrated that the resulting ankerite-like phase could be converted into ordered ankerite under hydrothermal conditions.We introduced the term“proto-ankerite”to define the Ca-Fe phases that possess near-ankerite stoichiometry but disordered cation arrangement.On the basis of the present study,we proposed herein that microbial activity is an important contributor to the genesis of sedimentary ankerite by providing the metastable Ca-Fe carbonate precursors.展开更多
The Ediacaran–Cambrian Phosphogenic Episode is the Earth’s first true phosphogenic event and resulted in worldwide phosphate deposits,which occurred during the processes of the Neoproterozoic Oxygenation Event.The E...The Ediacaran–Cambrian Phosphogenic Episode is the Earth’s first true phosphogenic event and resulted in worldwide phosphate deposits,which occurred during the processes of the Neoproterozoic Oxygenation Event.The Ediacaran Doushantuo Formation(ca.635–551 Ma)of Weng’an area in central Guizhou,South China,contains two economic phosphorite beds(the Lower and Upper Phosphorite Beds).This paper presents a detailed stratigraphic,sedimentological and mineralogical study of multiple outcrop and drill core sections of the Doushantuo Formation across the Weng’an area,and identified 11 lithofacies and 4 types of phosphatic grains.Significant differences in lithofacies and grain types between the upper and lower phosphate deposits are observed,indicating that the two sets of phosphate deposits are the products of two distinct phosphogenic processes.The Lower Phosphorite Bed mainly consists of banded and laminated phosphorites,contains micro-oncoids formed by microbially-mediated precipitation and peloids formed by in-situ chemically oscillating reactions,indicating a biochemical and chemical enrichment of phosphorus to sediments during the Early Ediacaran Period.The Upper Phosphorite Bed is mainly composed of carbonaceous,massive,and stromatolitic phosphorites,contains bioclasts(phosphatized spheroidal fossils),and intraclasts formed by hydrodynamic agitation,suggesting that the major accesses of phosphorus to sediments were the remineralization of organic P.Deposition of the two economic phosphorite beds was controlled by two sea-level cycles.Such differences have also been documented in contemporaneous phosphate-bearing successions in Brazil and Mangolia,indicating a significant shift in global phosphogenic mechanism during the early and middle Ediacaran,which may be due to the changes in redox conditions in seawater,associated with the Neoproterozoic Oxygenation Event.These regional active P-cycle processes could produce more free oxygen,which may have contributed to the upcoming Phanerozoic global oxidation.展开更多
Optical pulling provides a new degree of freedom in optical manipulation.It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field.Here,we theoretically ...Optical pulling provides a new degree of freedom in optical manipulation.It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field.Here,we theoretically propose and numerically demonstrate the realization of a long-range optical pulling force stemming from a self-induced gradient field in the manipulated object.In analogy to potential barriers in quantum tunnelling,we use a photonic band gap design in order to obtain the intensity gradients inside a manipulated object placed in a photonic crystal waveguide,thereby achieving a pulling force.Unlike the usual scattering-type optical pulling forces,the proposed gradient-field approach does not require precise elimination of the reflection from the manipulated objects.In particular,the Einstein-Laub formalism is applied to design this unconventional gradient force.The magnitude of the force can be enhanced by a factor of up to 50 at the optical resonance of the manipulated object in the waveguide,making it insensitive to absorption.The developed approach helps to break the limitation of scattering forces to obtain longrange optical pulling for manipulation and sorting of nanoparticles and other nano-objects.The developed principle of using the band gap to obtain a pulling force may also be applied to other types of waves,such as acoustic or water waves,which are important for numerous applications.展开更多
Structured light fields embody strong spatial variations of polarization,phase,and amplitude.Understanding,characterization,and exploitation of such fields can be achieved through their topological properties.Three-di...Structured light fields embody strong spatial variations of polarization,phase,and amplitude.Understanding,characterization,and exploitation of such fields can be achieved through their topological properties.Three-dimensional(3D)topological solitons,such as hopfions,are 3D localized continuous field configurations with nontrivial particle-like structures that exhibit a host of important topologically protected properties.Here,we propose and demonstrate photonic counterparts of hopfions with exact characteristics of Hopf fibration,Hopf index,and Hopf mapping from real-space vector beams to homotopic hyperspheres representing polarization states.We experimentally generate photonic hopfions with on-demand high-order Hopf indices and independently controlled topological textures,including Néel-,Bloch-,and antiskyrmionic types.We also demonstrate a robust free-space transport of photonic hopfions,thus showing the potential of hopfions for developing optical topological informatics and communications.展开更多
Organic light-emitting diode(OLED)is an electroluminescent technology that relies on charge-carrier dynamics and is a potential light source for variable environmental conditions.Here,by exploiting a self-developed lo...Organic light-emitting diode(OLED)is an electroluminescent technology that relies on charge-carrier dynamics and is a potential light source for variable environmental conditions.Here,by exploiting a self-developed low-temperature testing system,we investigated the characteristics of hole/electron transport,electro-optic conversion efficiency,and operation lifetime of OLEDs at low-temperature ranging from-40℃to 0℃and room temperature(25℃).Compared to devices operating at room temperature,the carrier transport capability is significantly decreased with reducing temperature,and especially the mobility of the hole-transporting material(HTM)and electron-transporting material(ETM)at-40℃decreases from 1.16×10-6 cm2/V·s and 2.60×10-4 cm2/V·s to 6.91×10-9 cm2/V·s and 1.44×10-5 cm2/V·s,respectively.Indeed,the temperature affects differently on the mobilities of HTM and ETM,which favors unbalanced charge-carrier transport and recombination in OLEDs,thereby leading to the maximum current efficiency decreased from 6.46 cd·A-1 at 25℃to 2.74 cd·A-1 at-40℃.In addition,blue fluorescent OLED at-20℃has an above 56%lifetime improvement(time to 80%of the initial luminance)over the reference device at room temperature,which is attributed to efficiently dissipating heat generated inside the device by the low-temperature environment.展开更多
The aggregation-induced emission(AIE) phenomenon provides a new direction for the development of organic light-emitting devices. Here, we present a new class of emitters based on 4,4-difluoro-4-bora-3 a,4 a-diaza-s-in...The aggregation-induced emission(AIE) phenomenon provides a new direction for the development of organic light-emitting devices. Here, we present a new class of emitters based on 4,4-difluoro-4-bora-3 a,4 a-diaza-s-indacene(BODIPY), functionalized at different positions with tetraphenylethylene(TPE), which is one of the most famous AIE luminogens. Thanks to this modification, we were able to tune the photoluminescence of the BODIPY moiety from the green to the near-infrared(NIR)spectral range and achieve PL efficiencies of ~50% in the solid state. Remarkably, we observed an enhancement of the AIE and up to ~100% photoluminescence efficiencies by blending the TPE-substituted BODIPY fluorophores with a poly[(9,9-di-noctylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)](F8 BT) matrix. By incorporating these blends in organic lightemitting diodes(OLEDs), we obtained electroluminescence peaked in the range 650–700 nm with up to 1.8% external quantum efficiency and ~2 m W/cm2 radiance, a remarkable result for red/NIR emitting and solution-processed OLEDs.展开更多
Polydimethylsiloxane(PDMS)is a dominant material in the fabrication of microfluidic devices to generate water-in-oil droplets,particularly lipid-stabilized droplets,because of its highly hydrophobic nature.However,its...Polydimethylsiloxane(PDMS)is a dominant material in the fabrication of microfluidic devices to generate water-in-oil droplets,particularly lipid-stabilized droplets,because of its highly hydrophobic nature.However,its key property of hydrophobicity has hindered its use in the microfluidic generation of oil-in-water droplets,which requires channels to have hydrophilic surface properties.In this article,we developed,optimized,and characterized a method to produce PDMS with a hydrophilic surface via the deposition of polyvinyl alcohol following plasma treatment and demonstrated its suitability for droplet generation.The proposed method is simple,quick,effective,and low cost and is versatile with respect to surfactants,with droplets being successfully generated using both anionic surfactants and more biologically relevant phospholipids.This method also allows the device to be selectively patterned with both hydrophilic and hydrophobic regions,leading to the generation of double emulsions and inverted double emulsions.展开更多
The electromagnetic field scattered by nano-objects contains a broad range of wavevectors and can be efficiently coupled to waveguided modes.The dominant contribution to scattering from subwavelength dielectric and pl...The electromagnetic field scattered by nano-objects contains a broad range of wavevectors and can be efficiently coupled to waveguided modes.The dominant contribution to scattering from subwavelength dielectric and plasmonic nanoparticles is determined by electric and magnetic dipolar responses.Here,we experimentally demonstrate spectral and phase selective excitation of Janus dipoles,sources with electric and magnetic dipoles oscillating out of phase,in order to control near-field interference and directional coupling to waveguides.We show that by controlling the polarisation state of the dipolar excitations and the excitation wavelength to adjust their relative contributions,directionality and coupling strength can be fully tuned.Furthermore,we introduce a novel spinning Janus dipole featuring cylindrical symmetry in the near and far field,which results in either omnidirectional coupling or noncoupling.Controlling the propagation of guided light waves via fast and robust near-field interference between polarisation components of a source is required in many applications in nanophotonics and quantum optics.展开更多
The microbial dolomite model has been used to interpret the origin of sedimentary dolomite.In this model,the formation of low-temperature protodolomite,an important precursor to sedimentary dolomite,can be facilitated...The microbial dolomite model has been used to interpret the origin of sedimentary dolomite.In this model,the formation of low-temperature protodolomite,an important precursor to sedimentary dolomite,can be facilitated either by actively metabolizing cells of anaerobic microbes and aerobic halophilic archaea or by their inactive biomass.Aerobic halophilic bacteria are widely distributed in(proto-)dolomite-depositing evaporitic environments and their biomass might serve as a template for the crystallization of protodolomite.To test this hypothesis,carbonation experiments were conducted using dead biomass of an aerobic halophilic bacterium(Exiguobacterium sp.strain JBHLT-3).Our results show that dead biomass of JBHLT-3 can accelerate Mg2+uptake in carbonate mineral precipitates.In addition,the amount of Mg incorporated into Ca-Mg carbonates is proportional to the concentration of biomass.High Mg-calcite is produced with 0.25 or 0.5 g/L biomass,whereas protodolomite forms with 1 g/L biomass.This is confirmed by the main Raman peak of Ca-Mg carbonates,which shifts towards higher wavenumbers with increased Mg substitution.Microbial cells and their imprints are preserved on the surface of high Mg-calcite and protodolomite.Hence,this study furthers our understanding of the dolomitization within buried and dead microbial mats,which provides useful insights into the origin of ancient dolomite.展开更多
Multimodal hard X-ray scanning probe microscopy has been extensively used to study functional materials providing multiple contrast mechanisms.For instance,combining ptychography with X-ray fluorescence(XRF)microscopy...Multimodal hard X-ray scanning probe microscopy has been extensively used to study functional materials providing multiple contrast mechanisms.For instance,combining ptychography with X-ray fluorescence(XRF)microscopy reveals structural and chemical properties simultaneously.While ptychography can achieve diffraction-limited spatial resolution,the resolution of XRF is limited by the X-ray probe size.Here,we develop a machine learning(ML)model to overcome this problem by decoupling the impact of the X-ray probe from the XRF signal.The enhanced spatial resolution was observed for both simulated and experimental XRF data,showing superior performance over the state-of-the-art scanning XRF method with different nano-sized X-ray probes.Enhanced spatial resolutions were also observed for the accompanying XRF tomography reconstructions.Using this probe profile deconvolution with the proposed ML solution to enhance the spatial resolution of XRF microscopy will be broadly applicable across both functional materials and biological imaging with XRF and other related application areas.展开更多
The Lomagundi-Jatuli Event(LJE) is one of the largest and earliest positive carbon isotope excursions preserving δ^(13)C_(carb) values between +5 and +16‰ in Paleoproterozoic carbonates worldwide. However, t...The Lomagundi-Jatuli Event(LJE) is one of the largest and earliest positive carbon isotope excursions preserving δ^(13)C_(carb) values between +5 and +16‰ in Paleoproterozoic carbonates worldwide. However, the duration, amplitude and patterns of these excursions remain poorly constrained. The 2.14-1.83 Ga Hutuo Group in the North China Craton is a 〉10 km thick volcano-sedimentary sequence, including 〉5 km thick well-preserved carbonates that were deposited in supra-tidal to sub-tidal environments. C-O isotopic and elemental analyses of 152 least altered samples of the carbonates revealed a three-stage δ^(13)C evolution. It began with an exclusively positive δ^(13)C_(carb)(+1.3 to + 3.4‰) stage in the ~2.1 Ga carbonate in the Dashiling and Qingshicun Formations, followed by a transition from positive values to oscillating positive and negative values in ~3 000 m thick carbonates of the Wenshan, Hebiancun, Jianancun, and Daguandong Formations, and end with exclusively negative δ^(13)C_(carb) values preserved in 〉 500 m thick dolostones of the Huaiyincun and Beidaxing Formations. It appears that much of the LJE, particularly those extremely positive δ^(13)C_(carb) signals, was not recorded in the Hutuo carbonates. The exclusively positive δ^(13)C_(carb) values(+1.3 to + 3.4‰) preserved in the lower formations likely correspond to the end of the LJE, whereas the subsequent two stages reflect the aftermath of the LJE and the onset of Shunga-Francevillian event(SFE). The present data point to an increased influence of oxygen on the carbon cycle from the Doucun to the Dongye Subgroups and demonstrate that the termination of the LJE in the North China Craton is nearly simultaneous with those in Fennoscandia and South Africa.展开更多
Visible light communication(VLC)is a wireless technology that relies on optical intensity modulation and is potentially a game changer for internet-of-things(IoT)connectivity.However,VLC is hindered by the low penetra...Visible light communication(VLC)is a wireless technology that relies on optical intensity modulation and is potentially a game changer for internet-of-things(IoT)connectivity.However,VLC is hindered by the low penetration depth of visible light in non-transparent media.One solution is to extend operation into the“nearly(in)visible”near-infrared(NIR,700-1000 nm)region,thus also enabling VLC in photonic bio-applications,considering the biological tissue NIR semitransparency,while conveniently retaining vestigial red emission to help check the link operativity by simple eye inspection.Here,we report new far-red/NIR organic light-emitting diodes(OLEDs)with a 650-800 nm emission range and external quantum efficiencies among the highest reported in this spectral range(>2.7%,with maximum radiance and luminance of 3.5 mW/cm^(2) and 260 cd/m^(2),respectively).With these OLEDs,we then demonstrate a“real-time”VLC setup achieving a data rate of 2.2 Mb/s,which satisfies the requirements for IoT and biosensing applications.These are the highest rates ever reported for an online unequalised VLC link based on solution-processed OLEDs.展开更多
As a critical component of coherent X-ray diffraction imaging(CDI),phase retrieval has been extensively applied in X-ray structural science to recover the 3D morphological information inside measured particles.Despite...As a critical component of coherent X-ray diffraction imaging(CDI),phase retrieval has been extensively applied in X-ray structural science to recover the 3D morphological information inside measured particles.Despite meeting all the oversampling requirements of Sayre and Shannon,current phase retrieval approaches still have trouble achieving a unique inversion of experimental data in the presence of noise.Here,we propose to overcome this limitation by incorporating a 3D Machine Learning(ML)model combining(optional)supervised learning with transfer learning.The trained ML model can rapidly provide an immediate result with high accuracy which could benefit real-time experiments,and the predicted result can be further refined with transfer learning.More significantly,the proposed ML model can be used without any prior training to learn the missing phases of an image based on minimization of an appropriate‘loss function’alone.We demonstrate significantly improved performance with experimental Bragg CDI data over traditional iterative phase retrieval algorithms.展开更多
The energy gap law(E_(G)-law)and aggregation quenching are the main limitations to overcome in the design of near-infrared(NIR)organic emitters.Here,we achieve unprecedented results by synergistically addressing both ...The energy gap law(E_(G)-law)and aggregation quenching are the main limitations to overcome in the design of near-infrared(NIR)organic emitters.Here,we achieve unprecedented results by synergistically addressing both of these limitations.First,we propose porphyrin oligomers with increasing length to attenuate the effects of the E_(G)-law by suppressing the non-radiative rate growth,and to increase the radiative rate via enhancement of the oscillator strength.Second,we design side chains to suppress aggregation quenching.We find that the logarithmic rate of variation in the non-radiative rate vs.E_(G)is suppressed by an order of magnitude with respect to previous studies,and we complement this breakthrough by demonstrating organic light-emitting diodes with an average external quantum efficiency of-1.1%,which is very promising for a heavy-metal-free 850 nm emitter.We also present a novel quantitative model of the internal quantum efficiency for active layers supporting triplet-to-singlet conversion.These results provide a general strategy for designing high-luminance NIR emitters.展开更多
基金supported by Grants from the UK EPSRC Future Compound Semiconductor Manufacturing Hub(EP/P006973/1)the financial support from EPSRC(EP/L018330/1,EP/N032888/1)+3 种基金the U.S.Army Research Laboratory under Cooperative Agreement Number W911NF-16-2-0120the “973 Program—the National Basic Research Program of China” Special Funds for the Chief Young Scientis(2015CB358600)the Excellent Young Scholar Fund from National Natural Science Foundation of China(21422103)the China Scholarship Council(CSC)
文摘Ternary transition metal dichalcogenide alloys with spatially graded bandgaps are an emerging class of two-dimensional materials with unique features,which opens up new potential for device applications.Here,visible–near-infrared and self-powered phototransistors based on spatially bandgap-graded MoS2(1−x)Se2x alloys,synthesized by a simple and controllable chemical solution deposition method,are reported.The graded bandgaps,arising from the spatial grading of Se composition and thickness within a single domain,are tuned from 1.83 to 1.73 eV,leading to the formation of a homojunction with a builtin electric field.Consequently,a strong and sensitive gate-modulated photovoltaic effect is demonstrated,enabling the homojunction phototransistors at zero bias to deliver a photoresponsivity of 311 mA W−1,a specific detectivity up to^10^11 Jones,and an on/off ratio up to^10^4.Remarkably,when illuminated by the lights ranging from 405 to 808 nm,the biased devices yield a champion photoresponsivity of 191.5 A W−1,a specific detectivity up to^1012 Jones,a photoconductive gain of 10^6–10^7,and a photoresponsive time in the order of^50 ms.These results provide a simple and competitive solution to the bandgap engineering of two-dimensional materials for device applications without the need for p–n junctions.
基金This research was jointly supported by the National Natural Science Foundation of China(Grant Nos.42272046,42293292 and 42072336)the National Key R&D Program of China(Grant No.2022YFF0800304)the 111 Project(Grant No.BP0820004).
文摘The origin of sedimentary dolomite has become a long-standing problem in the Earth Sciences.Some carbonate minerals like ankerite have the same crystal structure as dolomite,hence their genesis may provide clues to help solving the dolomite problem.The purpose of this study was to probe whether microbial activity can be involved in the formation of ankerite.Bio-carbonation experiments associated with microbial iron reduction were performed in batch systems with various concentrations of Ca^(2+)(0–20 mmol/L),with a marine iron-reducing bacterium Shewanella piezotolerans WP3 as the reaction mediator,and with lactate and ferrihydrite as the respective electron donor and acceptor.Our biomineralization data showed that Ca-amendments expedited microbially-mediated ferrihydrite reduction by enhancing the adhesion between WP3 cells and ferrihydrite particles.After bioreduction,siderite occurred as the principal secondary mineral in the Ca-free systems.Instead,Ca-Fe carbonates were formed when Ca^(2+)ions were present.The CaCO_(3) content of microbially-induced Ca-Fe carbonates was positively correlated with the initial Ca2+concentration.The Ca-Fe carbonate phase produced in the 20 mmol/L Ca-amended biosystems had a chemical formula of Ca_(0.8)Fe_(1.2)(CO_(3))_(2),which is close to the theoretical composition of ankerite.This ankeritelike phase was nanometric in size and spherical,Ca-Fe disordered,and structurally defective.Our simulated diagenesis experiments further demonstrated that the resulting ankerite-like phase could be converted into ordered ankerite under hydrothermal conditions.We introduced the term“proto-ankerite”to define the Ca-Fe phases that possess near-ankerite stoichiometry but disordered cation arrangement.On the basis of the present study,we proposed herein that microbial activity is an important contributor to the genesis of sedimentary ankerite by providing the metastable Ca-Fe carbonate precursors.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB26020102)the National Natural Science Foundation of China(No.41272038)+1 种基金the State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(No.GBL12001)Guizhou Provincial Department of Science and Technology Guizhou Science Foundation(No.[2016]1407).
文摘The Ediacaran–Cambrian Phosphogenic Episode is the Earth’s first true phosphogenic event and resulted in worldwide phosphate deposits,which occurred during the processes of the Neoproterozoic Oxygenation Event.The Ediacaran Doushantuo Formation(ca.635–551 Ma)of Weng’an area in central Guizhou,South China,contains two economic phosphorite beds(the Lower and Upper Phosphorite Beds).This paper presents a detailed stratigraphic,sedimentological and mineralogical study of multiple outcrop and drill core sections of the Doushantuo Formation across the Weng’an area,and identified 11 lithofacies and 4 types of phosphatic grains.Significant differences in lithofacies and grain types between the upper and lower phosphate deposits are observed,indicating that the two sets of phosphate deposits are the products of two distinct phosphogenic processes.The Lower Phosphorite Bed mainly consists of banded and laminated phosphorites,contains micro-oncoids formed by microbially-mediated precipitation and peloids formed by in-situ chemically oscillating reactions,indicating a biochemical and chemical enrichment of phosphorus to sediments during the Early Ediacaran Period.The Upper Phosphorite Bed is mainly composed of carbonaceous,massive,and stromatolitic phosphorites,contains bioclasts(phosphatized spheroidal fossils),and intraclasts formed by hydrodynamic agitation,suggesting that the major accesses of phosphorus to sediments were the remineralization of organic P.Deposition of the two economic phosphorite beds was controlled by two sea-level cycles.Such differences have also been documented in contemporaneous phosphate-bearing successions in Brazil and Mangolia,indicating a significant shift in global phosphogenic mechanism during the early and middle Ediacaran,which may be due to the changes in redox conditions in seawater,associated with the Neoproterozoic Oxygenation Event.These regional active P-cycle processes could produce more free oxygen,which may have contributed to the upcoming Phanerozoic global oxidation.
基金Q.D.thanks for the financial support from the Natural Science Foundation of Guangdong Province,China(2019A1515011578)Department of Science and Technology of Guangdong Province,China(2020B1212060067)A.K.and A.Z.work was supported by the ERC iCOMM project(789340).
文摘Optical pulling provides a new degree of freedom in optical manipulation.It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field.Here,we theoretically propose and numerically demonstrate the realization of a long-range optical pulling force stemming from a self-induced gradient field in the manipulated object.In analogy to potential barriers in quantum tunnelling,we use a photonic band gap design in order to obtain the intensity gradients inside a manipulated object placed in a photonic crystal waveguide,thereby achieving a pulling force.Unlike the usual scattering-type optical pulling forces,the proposed gradient-field approach does not require precise elimination of the reflection from the manipulated objects.In particular,the Einstein-Laub formalism is applied to design this unconventional gradient force.The magnitude of the force can be enhanced by a factor of up to 50 at the optical resonance of the manipulated object in the waveguide,making it insensitive to absorption.The developed approach helps to break the limitation of scattering forces to obtain longrange optical pulling for manipulation and sorting of nanoparticles and other nano-objects.The developed principle of using the band gap to obtain a pulling force may also be applied to other types of waves,such as acoustic or water waves,which are important for numerous applications.
基金the National Natural Science Foundation of China(Grant Nos.62075050,11934013,and 61975047)the High-Level Talents Project of Heilongjiang Province(Grant No.2020GSP12)the European Research Council iCOMM project(Grant No.789340).
文摘Structured light fields embody strong spatial variations of polarization,phase,and amplitude.Understanding,characterization,and exploitation of such fields can be achieved through their topological properties.Three-dimensional(3D)topological solitons,such as hopfions,are 3D localized continuous field configurations with nontrivial particle-like structures that exhibit a host of important topologically protected properties.Here,we propose and demonstrate photonic counterparts of hopfions with exact characteristics of Hopf fibration,Hopf index,and Hopf mapping from real-space vector beams to homotopic hyperspheres representing polarization states.We experimentally generate photonic hopfions with on-demand high-order Hopf indices and independently controlled topological textures,including Néel-,Bloch-,and antiskyrmionic types.We also demonstrate a robust free-space transport of photonic hopfions,thus showing the potential of hopfions for developing optical topological informatics and communications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775130 and 11974236)the Science and Technology Commission of Shanghai Municipality Program,China(Grant Nos.19DZ2281000 and 17DZ2281000)the Research Innovation Program for College Graduates of Jiangsu Province,China(Grant Nos.KYCX202545 and KYCX202549)。
文摘Organic light-emitting diode(OLED)is an electroluminescent technology that relies on charge-carrier dynamics and is a potential light source for variable environmental conditions.Here,by exploiting a self-developed low-temperature testing system,we investigated the characteristics of hole/electron transport,electro-optic conversion efficiency,and operation lifetime of OLEDs at low-temperature ranging from-40℃to 0℃and room temperature(25℃).Compared to devices operating at room temperature,the carrier transport capability is significantly decreased with reducing temperature,and especially the mobility of the hole-transporting material(HTM)and electron-transporting material(ETM)at-40℃decreases from 1.16×10-6 cm2/V·s and 2.60×10-4 cm2/V·s to 6.91×10-9 cm2/V·s and 1.44×10-5 cm2/V·s,respectively.Indeed,the temperature affects differently on the mobilities of HTM and ETM,which favors unbalanced charge-carrier transport and recombination in OLEDs,thereby leading to the maximum current efficiency decreased from 6.46 cd·A-1 at 25℃to 2.74 cd·A-1 at-40℃.In addition,blue fluorescent OLED at-20℃has an above 56%lifetime improvement(time to 80%of the initial luminance)over the reference device at room temperature,which is attributed to efficiently dissipating heat generated inside the device by the low-temperature environment.
基金supported by the European Community’s Seventh Framework Programme (FP7/2007-2013) (607585)
文摘The aggregation-induced emission(AIE) phenomenon provides a new direction for the development of organic light-emitting devices. Here, we present a new class of emitters based on 4,4-difluoro-4-bora-3 a,4 a-diaza-s-indacene(BODIPY), functionalized at different positions with tetraphenylethylene(TPE), which is one of the most famous AIE luminogens. Thanks to this modification, we were able to tune the photoluminescence of the BODIPY moiety from the green to the near-infrared(NIR)spectral range and achieve PL efficiencies of ~50% in the solid state. Remarkably, we observed an enhancement of the AIE and up to ~100% photoluminescence efficiencies by blending the TPE-substituted BODIPY fluorophores with a poly[(9,9-di-noctylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)](F8 BT) matrix. By incorporating these blends in organic lightemitting diodes(OLEDs), we obtained electroluminescence peaked in the range 650–700 nm with up to 1.8% external quantum efficiency and ~2 m W/cm2 radiance, a remarkable result for red/NIR emitting and solution-processed OLEDs.
基金This work was supported by the EPSRC(grants EP/K038648/1 and EP/J017566/1)by an EPSRC Fellowship awarded to YE(grant EP/N016998/1).
文摘Polydimethylsiloxane(PDMS)is a dominant material in the fabrication of microfluidic devices to generate water-in-oil droplets,particularly lipid-stabilized droplets,because of its highly hydrophobic nature.However,its key property of hydrophobicity has hindered its use in the microfluidic generation of oil-in-water droplets,which requires channels to have hydrophilic surface properties.In this article,we developed,optimized,and characterized a method to produce PDMS with a hydrophilic surface via the deposition of polyvinyl alcohol following plasma treatment and demonstrated its suitability for droplet generation.The proposed method is simple,quick,effective,and low cost and is versatile with respect to surfactants,with droplets being successfully generated using both anionic surfactants and more biologically relevant phospholipids.This method also allows the device to be selectively patterned with both hydrophilic and hydrophobic regions,leading to the generation of double emulsions and inverted double emulsions.
基金supported by European Research Council Starting Grant ERC-2016-STG-714151-PSINFONI,EPSRC(UK)ERC iCOMM project(789340)support from the Royal Society and the Wolfson Foundation.
文摘The electromagnetic field scattered by nano-objects contains a broad range of wavevectors and can be efficiently coupled to waveguided modes.The dominant contribution to scattering from subwavelength dielectric and plasmonic nanoparticles is determined by electric and magnetic dipolar responses.Here,we experimentally demonstrate spectral and phase selective excitation of Janus dipoles,sources with electric and magnetic dipoles oscillating out of phase,in order to control near-field interference and directional coupling to waveguides.We show that by controlling the polarisation state of the dipolar excitations and the excitation wavelength to adjust their relative contributions,directionality and coupling strength can be fully tuned.Furthermore,we introduce a novel spinning Janus dipole featuring cylindrical symmetry in the near and far field,which results in either omnidirectional coupling or noncoupling.Controlling the propagation of guided light waves via fast and robust near-field interference between polarisation components of a source is required in many applications in nanophotonics and quantum optics.
基金jointly supported by the National Natural Science Foundation of China(Nos.42272046,42072336 and 41772362)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB26000000)+1 种基金the 111 Project of China(No.BP0820004)the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(No.CUGCJ1703)。
文摘The microbial dolomite model has been used to interpret the origin of sedimentary dolomite.In this model,the formation of low-temperature protodolomite,an important precursor to sedimentary dolomite,can be facilitated either by actively metabolizing cells of anaerobic microbes and aerobic halophilic archaea or by their inactive biomass.Aerobic halophilic bacteria are widely distributed in(proto-)dolomite-depositing evaporitic environments and their biomass might serve as a template for the crystallization of protodolomite.To test this hypothesis,carbonation experiments were conducted using dead biomass of an aerobic halophilic bacterium(Exiguobacterium sp.strain JBHLT-3).Our results show that dead biomass of JBHLT-3 can accelerate Mg2+uptake in carbonate mineral precipitates.In addition,the amount of Mg incorporated into Ca-Mg carbonates is proportional to the concentration of biomass.High Mg-calcite is produced with 0.25 or 0.5 g/L biomass,whereas protodolomite forms with 1 g/L biomass.This is confirmed by the main Raman peak of Ca-Mg carbonates,which shifts towards higher wavenumbers with increased Mg substitution.Microbial cells and their imprints are preserved on the surface of high Mg-calcite and protodolomite.Hence,this study furthers our understanding of the dolomitization within buried and dead microbial mats,which provides useful insights into the origin of ancient dolomite.
基金This work uses the 3-ID Hard X-ray Nanoprobe(HXN)beamline of the National Synchrotron Light Source II(NSLS-II),which was supported by the U.S.Department of Energy(DOE).NSLS-II is an Office of Science user facility operated by Brookhaven National Laboratory under Contract No.DE-SC0012704.The work at UCL was supported by EPSRCThis work was partially carried out at the MERF facility at Argonne National Laboratory,which is supported within the core funding of the Applied Battery Research for Transportation Program.Argonne,a U.S.DOE,Office of Science laboratory,is operated under Contract No.DE-AC02-06CH11357.We acknowledge the support of the U.S.DOE,Office of Energy Efficiency and Renewable Energy,Vehicle Technologies Office,and in particular the support of Peter Faguy and Dave Howell.
文摘Multimodal hard X-ray scanning probe microscopy has been extensively used to study functional materials providing multiple contrast mechanisms.For instance,combining ptychography with X-ray fluorescence(XRF)microscopy reveals structural and chemical properties simultaneously.While ptychography can achieve diffraction-limited spatial resolution,the resolution of XRF is limited by the X-ray probe size.Here,we develop a machine learning(ML)model to overcome this problem by decoupling the impact of the X-ray probe from the XRF signal.The enhanced spatial resolution was observed for both simulated and experimental XRF data,showing superior performance over the state-of-the-art scanning XRF method with different nano-sized X-ray probes.Enhanced spatial resolutions were also observed for the accompanying XRF tomography reconstructions.Using this probe profile deconvolution with the proposed ML solution to enhance the spatial resolution of XRF microscopy will be broadly applicable across both functional materials and biological imaging with XRF and other related application areas.
基金National Natural Science Foundation of China (No. 41272038)National Universities, China University of Geosciences (Wuhan), State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences (No. GKZ14Y660)+1 种基金the 111 Program for the Ministry of Education of Chinathe State Administration of Foreign Expert Affairs of China (No. B07039)
文摘The Lomagundi-Jatuli Event(LJE) is one of the largest and earliest positive carbon isotope excursions preserving δ^(13)C_(carb) values between +5 and +16‰ in Paleoproterozoic carbonates worldwide. However, the duration, amplitude and patterns of these excursions remain poorly constrained. The 2.14-1.83 Ga Hutuo Group in the North China Craton is a 〉10 km thick volcano-sedimentary sequence, including 〉5 km thick well-preserved carbonates that were deposited in supra-tidal to sub-tidal environments. C-O isotopic and elemental analyses of 152 least altered samples of the carbonates revealed a three-stage δ^(13)C evolution. It began with an exclusively positive δ^(13)C_(carb)(+1.3 to + 3.4‰) stage in the ~2.1 Ga carbonate in the Dashiling and Qingshicun Formations, followed by a transition from positive values to oscillating positive and negative values in ~3 000 m thick carbonates of the Wenshan, Hebiancun, Jianancun, and Daguandong Formations, and end with exclusively negative δ^(13)C_(carb) values preserved in 〉 500 m thick dolostones of the Huaiyincun and Beidaxing Formations. It appears that much of the LJE, particularly those extremely positive δ^(13)C_(carb) signals, was not recorded in the Hutuo carbonates. The exclusively positive δ^(13)C_(carb) values(+1.3 to + 3.4‰) preserved in the lower formations likely correspond to the end of the LJE, whereas the subsequent two stages reflect the aftermath of the LJE and the onset of Shunga-Francevillian event(SFE). The present data point to an increased influence of oxygen on the carbon cycle from the Doucun to the Dongye Subgroups and demonstrate that the termination of the LJE in the North China Craton is nearly simultaneous with those in Fennoscandia and South Africa.
基金funding by EPSRC(grant EP/P006280/1,MARVEL)financial support from the National Centre for Research and Development,Poland(PL-TWIII/17/2016)the National Science Centre,Poland(Grant HARMONIA 2016/22/M/ST5/00431).
文摘Visible light communication(VLC)is a wireless technology that relies on optical intensity modulation and is potentially a game changer for internet-of-things(IoT)connectivity.However,VLC is hindered by the low penetration depth of visible light in non-transparent media.One solution is to extend operation into the“nearly(in)visible”near-infrared(NIR,700-1000 nm)region,thus also enabling VLC in photonic bio-applications,considering the biological tissue NIR semitransparency,while conveniently retaining vestigial red emission to help check the link operativity by simple eye inspection.Here,we report new far-red/NIR organic light-emitting diodes(OLEDs)with a 650-800 nm emission range and external quantum efficiencies among the highest reported in this spectral range(>2.7%,with maximum radiance and luminance of 3.5 mW/cm^(2) and 260 cd/m^(2),respectively).With these OLEDs,we then demonstrate a“real-time”VLC setup achieving a data rate of 2.2 Mb/s,which satisfies the requirements for IoT and biosensing applications.These are the highest rates ever reported for an online unequalised VLC link based on solution-processed OLEDs.
基金Work at Brookhaven National Laboratory was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-SC0012704J.D.received funding from the China Scholarship Council(CSC).Work at UCL was funded by EPSRC.Measurements were carried out at the Advanced Photon Source(APS)beamline 34-ID-C,which was supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-06CH11357The beamline 34-ID-C was built with U.S.National Science Foundation grant DMR-9724294.
文摘As a critical component of coherent X-ray diffraction imaging(CDI),phase retrieval has been extensively applied in X-ray structural science to recover the 3D morphological information inside measured particles.Despite meeting all the oversampling requirements of Sayre and Shannon,current phase retrieval approaches still have trouble achieving a unique inversion of experimental data in the presence of noise.Here,we propose to overcome this limitation by incorporating a 3D Machine Learning(ML)model combining(optional)supervised learning with transfer learning.The trained ML model can rapidly provide an immediate result with high accuracy which could benefit real-time experiments,and the predicted result can be further refined with transfer learning.More significantly,the proposed ML model can be used without any prior training to learn the missing phases of an image based on minimization of an appropriate‘loss function’alone.We demonstrate significantly improved performance with experimental Bragg CDI data over traditional iterative phase retrieval algorithms.
基金funding by EPSRC(grant EP/P006280/1,MARVEL)the European Community's Seventh Framework Programme(FP7/2007-2013)ITN MSCA action under Grant Agreement No.607585(OSNIRO)the H2020 ETN MSCA action under grant agreement 643238(SYNCHRONICS).
文摘The energy gap law(E_(G)-law)and aggregation quenching are the main limitations to overcome in the design of near-infrared(NIR)organic emitters.Here,we achieve unprecedented results by synergistically addressing both of these limitations.First,we propose porphyrin oligomers with increasing length to attenuate the effects of the E_(G)-law by suppressing the non-radiative rate growth,and to increase the radiative rate via enhancement of the oscillator strength.Second,we design side chains to suppress aggregation quenching.We find that the logarithmic rate of variation in the non-radiative rate vs.E_(G)is suppressed by an order of magnitude with respect to previous studies,and we complement this breakthrough by demonstrating organic light-emitting diodes with an average external quantum efficiency of-1.1%,which is very promising for a heavy-metal-free 850 nm emitter.We also present a novel quantitative model of the internal quantum efficiency for active layers supporting triplet-to-singlet conversion.These results provide a general strategy for designing high-luminance NIR emitters.