The translational capability of the instrument for human GI tract imaging was characterized with an Archimedean spiral phantom consisting of twelve 100 µm sutures, a stainless steel mesh with a pitch of 3 mm and an ex vivo pig esophagus sample. We estimated an imaging penetration depth of ~0.84 mm in vivo by immersing the mesh phantom in intralipid solution to simulate light scattering in human esophageal tissue and validated our findings ex vivo using pig esophagus. This proof-of-concept study demonstrates the translational potential of the proposed video-rate endoscope for human GI tract imaging.Gastrointestinal (GI) endoscopy is a common medical diagnostic procedure used for esophageal cancer detection. Current emerging capsule optoacoustic endoscopes, however, suffer from low pulse repetition rates and slow scanning units limit attainable imaging frame rates. Consequently, motion artifacts result in inaccurate spatial mapping and misinterpretation of data. To overcome these limitations, we report a 360 Furthermore, proximal rotation via torque coils are problematic due to uncontrolled coil friction causing heat, limiting the rotation speed, and affecting scanning uniformity during operation. Loss of scanning uniformity results in loss of image formation accuracy. The above-mentioned configurations Existing implementations of OA endoscopy include a 4 Hz-distal rotation endoscope which was employed in simultaneous optoacoustic and ultrasonic endoscopy for imaging internal organs of a rabbit 3 at 0.24 Hz. To simulate scattering of light in esophageal tissue, the acoustic coupling medium of water was replaced with various concentrations of an intralipid solution to determine an estimated penetration depth of ~0.84 mm in the human esophagus. To validate the estimated penetrated depth, we imaged an ex vivo pig esophagus. Our results demonstrate proof-of-principle translational potential of optoacoustic endoscopy for delivering video-rate 3D functional information of the human esophagus.Clinical translation of current OA capsule endoscopes are limited by their slow scanning speeds. Our approach reported herein instead offers video rate (50 Hz), 360-degrees, side-looking OA signal acquisition by implementing distal rotation coupling of the acoustic sensor and laser illumination, paving the way towards clinical translational of OA capsule endoscopy of the GI track. We characterized the endoscope’s lateral resolution by imaging a phantom consisting of twelve 100 µm sutures arranged in an Archimedean spiral with a pitch of 3 mm, and demonstrated a volumetric pullback spiral scan over 1790 mm2The benchtop optoacoustic endoscope unit as illustrated in 3) active element transducer with a 6 mm-fused silica acoustic lens, and a central aperture of 2 mm in diameter to allow coaxial illumination . To facilitate side illumination, the transducer is integrates a 90° silver coated optical reflector with > 95% reflectivity at 532 nm, surface flatness of λ/4, and surface quality of 60–40 scratch-dig. Furthermore, a sealing window manufactured with PMMA altuglas SG7 with a thickness of 1 mm was installed at the central aperture of the detector. The optical beam was a low divergence beam with a half divergence angle of 3.9° and focal length of 7.4 mm along the air and water optical path length inside the capsule. Full 360° unobstructed field of view is achieved by implementing customized low friction miniature gold slip rings  to enable electrical coupling of high frequency ultrasound signals, thereby avoiding obstruction from driving cables over the field of view. The capsule is encapsulated in water with a cylindrical PMMA capsule lid featuring a thin fiducial marker used for synchronization and interpolation of high frame rate B scans.The proposed 16 mm diameter semi-capsule prototype consists of a miniature motor with an ultrafine hollow shaft  to allow for coaxial low–beam divergence optoacoustic illumination with a custom designed GRIN lens mounted to the distal end of the multimode optical fiber with a core diameter of 105 µm and numerical aperture of 0.2 . The detector features a 28 MHz-central frequency, side-looking, planar lithium niobate  and connected to a T-bias  prior to data acquisition at a sampling rate of 500 MHz. The T-bias is used to provide a DC voltage supply to the pre-amplifier circuit while remaining decoupled from the radiofrequency (RF) line of the transducer, hence voltage fluctuations from the DC voltage source do not affect the RF signal. The semi capsule prototype was mounted to an XYZ linear motorized stage (MTS50-Z8 in 3-axis XYZ Configuration Thorlabs) to allow for controlled repositioning and performed 3D Helical pull-back scans. The optoacoustic data was acquired by a ATS9373 DAQ card  synchronized to the board’s external trigger port via the photodetector signal. Signal processing was controlled by LabVIEW and data analyzed in MATLAB.The endoscopic transducer was characterized by linear raster scanning the semi capsule against a 20 µm suture in the YZ plane by shifting the transducer away from the acoustic source generated via the suture  to determine the temporal/frequency response at focus, the axial/lateral resolutions, and depth-of-focus See .To demonstrate 50 Hz B-scan frame rate with 100 kHz pulse repetition rate (3). This experiment was repeated by replenishing the acoustic coupling medium with controlled titration concentrations of intralipid (IL) solution to simulate the scattering of light during the interrogation of human esophageal tissue. A 20% IL solution was diluted to six test IL concentrations including 0.015%, 0.031%, 0.062%, 0.125%, 0.25% and 0.5%. The main molecular absorber in mucosa at 532 nm is hemoglobin, which is in circulation in blood vessels (simulated by the mesh) whereas the connective tissue in mucosa acts primarily as a scattering medium at this wavelength (simulated by the IL). The detection depth limit was defined by the deepest position where the signal is greater than the system noise level of 1 mV, which is SNR= 1 for the intralipid mesh experiment shown in A 3D helical pull back optoacoustic scan over 10 mm of a stainless steel mesh arranged in an Archimedean spiral with a pitch of 3 mm a was perex vivo pig esophageal sample mounted inside a 50 mL-Falcon tube to demonstrate translational potential. In an attempt to preserve the vascular network in the esophagus during sample extracting, a heated blade was used to cut and seal each end of the esophagus. The pulse laser energy was measured at the capsule surface during all imaging and was maintained at ~12 µJ per pulse. Energy measurements were initially made using an Ophir energy meter (model PE10-C) which can operate up to a pulse repetition rate of 25 kHz. The OA signal strength generated by a reference marker was used as a surrogate monitor of the pulse energy for repetition rates beyond the limit of the energy meter to keep the pulse energy The same scanning configuration was also performed on an 33.1The structure and setup of the proposed endoscopic transducer is shown in 3.2To characterize endoscope’s lateral resolution performance as a function of laser pulse repetition rate and scanning speed, we first imaged a phantom comprised of twelve 100 µm sutures arranged in an Archimedean spiral with a pitch of 3 mm a. Fig. 2To assess the influence of the arc sampling interval and scanning speed on the lateral resolution at focus, we acquired continuous scans at the maximum frame rate (50 Hz) with different laser pulse repetition rates (20–100 kHz), followed by scans at the maximum repetition rate (100 kHz) with different frame rates (10–50 Hz). For each case we acquired a set of 10 continuous revolutions and calculated the lateral resolution for each rotation scan. The median and interquartile ranges (IQR) of the measurements were used as indicators of resolution and variability for each condition.Table (c) in Table (d) in Overall, by reducing the B scan frame rate and using a higher laser pulse repetition rate, arc sampling intervals are reduced during measurement which, however, results in an increased number of A scans per revolution, impacting file size and memory management. Nevertheless, our results show arc sampling intervals below 18.8 µm obtained using a 30 Hz scan rate and 100 kHz repetition rate, indicating no significant improvement in the median value of the lateral resolution corresponding to one tenth of the transducer lateral resolution.3.3We next set out to demonstrate the volumetric imaging capability of the endoscope. We performed a Cscan of a stainless steel mesh at 50 Hz B-scan rate arranged in an Archimedean spiral set at a pitch of 3 mm a which s3.4To assess the imaging penetration depth of the endoscope under light scattering conditions mimicking those of the human esophagus, we embedded the mesh in an intralipid (IL) solution at different concentrations. The maximum intensity projections from the top and side views of the volumetric scans were obtained and the fiducial marker masked out to avoid signal saturation and to restrict the analysis to intensities within the dynamic range from the mesh in the scattering media.At 0.015% IL a and b, Light scattering and diffusion affects the amount of light available for OA generation from tissue. To estimate the expected imaging depth in the human esophagus, we calculated the reduced scattering coefficient, rate see .3.5ex vivo female pig esophagus  is not violated (see supplementary). Under these conditions He et al. 2 is no longer an applicable limit. In our case, the MPE limit is 1.53 mJ/cm2 (see 2, and following the limited aperture criterion of 3.5 mm of the ANSI standard, the MPE is exceeded by 174-fold in this case. These findings demonstrate that the translational potential of optoacoustic endoscopy is driven by the ability to rapidly scan the human esophagus, albeit currently exceeding the MPE by a factor of 4, while offering high resolution over several mm’s of depth.This depth is on par with previous OA studies, demonstrating images of small animal esophagus or colon tissue with penetration depths of ~ 1 mm in vivo at < 5 Hz /cm2 see . PreviouThe ex vivo performance of the optoacoustic capsule design presented herein represents a significant leap toward video-rate in vivo optoacoustic endoscopy of the human GI tract. For in vivo measurements, we anticipate that the capsule will stretch the esophageal track and thereby achieve optimal contact between the tissue surface and capsule by peristaltic force. More sophisticated balloon configurations could alternatively be explored. However, in order to translate the design for in vivo imaging, future efforts are required to address capsule size, sensitivity, resolution and motor stability compensation. While our current capsule design has a diameter of 16 mm, similar to standard WLSE, further miniaturization is required to ease swallowing and match the size of commercially available white light capsules, with sizes typically less than 32 mm in length and 13 mm in diameter ex vivo pig esophagus where lateral resolution accuracy and imaging depth, respectively, were demonstrated. Overall, these experimental results suggest that the novel video-rate optoacoustic capsule endoscope design can mitigate motion artefacts during imaging, offering promising translational characteristics for human GI tract molecular imaging in the future.In conclusion, a 16 mm optoacoustic capsule endoscope prototype with a side viewing central aperture endoscopic transducer with integrated optics and slips rings allowed for full field of view optoacoustic imaging at 50 Hz frame rate with angular sampling resolution of 0.18º attributed to the 100 kHz pulse repetition rate. Its functional potential was assessed in phantoms and an The authors declare no conflict of interest.


Atlantic Niño is the Atlantic equivalent of El Niño-Southern Oscillation (ENSO), and it has prominent impacts on regional and global climate. Existing studies suggest that the Atlantic Niño may arise from local atmosphere-ocean interaction and is sometimes triggered by the Atlantic Meridional Mode (AMM), with overall weak ENSO contribution. By analyzing observational datasets and performing numerical model experiments, here we show that the Atlantic Niño can be induced by the Indian Ocean Dipole (IOD). We find that the enhanced rainfall in the western tropical Indian Ocean during positive IOD weakens the easterly trade winds over the tropical Atlantic, causing warm anomalies in the central and eastern equatorial Atlantic basin and therefore triggering the Atlantic Niño. Our finding suggests that the cross-basin impact from the tropical Indian Ocean plays a more important role in affecting interannual climate variability than previously thought. The Atlantic Niño is an important mode of tropical Atlantic variability that influences the climate conditions in surrounding areas. Here, the authors use observational data and model simulations to show that positive phases of the Indian Ocean Dipole can trigger Atlantic Niño events. This climate phenomenon is called El Niño, the positive phase of El Niño-Southern Oscillation (ENSO), in the tropical Pacific2 and is referred to as the Atlantic Niño in the tropical Atlantic3.In the tropical Pacific and Atlantic Oceans, the mean sea surface temperature (SST) is warm in the west and cold in the east, under the influence of prevailing easterly trade wind forcing. The east-west SST gradient, however, is substantially weakened or even reversed in some years, which is accompanied by a significant slackening of the trade winds6. For instance, the Atlantic Niño enhances seasonal rainfall over South America and Africa8; it can also affect the African Easterly Jet9, which can subsequently influence Atlantic hurricanes11. It has been suggested that the Atlantic Niño may strengthen the Pacific Walker circulation and lead to La Niña15, the negative phase of ENSO. Through atmospheric teleconnection, the Atlantic Niño can also weaken the Indian summer monsoon18. Therefore, understanding and predicting the Atlantic Niño are of paramount importance and have large societal benefits.The Atlantic Niño is associated with prominent climate anomalies across the tropical Atlantic and has far-reaching impacts on climate in remote regions20, but some events may peak in late fall and winter22. Its development involves positive feedbacks between atmosphere and ocean24. During the Atlantic Niño, warm SST anomalies (SSTA) appear in the central and eastern tropical Atlantic basin, which lowers the sea level pressure (SLP) in the region. The associated eastward SLP gradient force induces westerly wind anomalies, which cause anomalous surface Ekman convergence, deepen the thermocline, reduce oceanic upwelling cooling and thus further increase the warm SSTA in the eastern basin. In addition, the anomalous westerlies weaken the westward South Equatorial Current and produce eastward heat advection anomalies, enhancing the warm SSTA. Surface heat flux anomalies do not contribute much to the warm SSTA associated with the Atlantic Niño25.Unlike ENSO that peaks in boreal winter, the Atlantic Niño is generally phase-locked to boreal summer26 may help trigger the Atlantic Niño. El Niño can induce wind anomalies over tropical Atlantic28, which excite oceanic waves that warm the eastern tropical Atlantic SST20. This remote ENSO influence however is overall weak29, partly due to the opposing effects of the anomalous equatorial easterlies (which generate upwelling Kelvin wave) and off-equatorial anticyclonic wind anomalies (which generate downwelling Rossby wave)30. Indeed, warm but weak SSTA is only found north of the Atlantic equator during El Niño 33. Whilst most existing studies focus on tropical Indian–Pacific and Pacific–Atlantic interactions, interaction between the tropical Indian and Atlantic Oceans is much less explored. The role played by variability of the tropical Indian Ocean in triggering the Atlantic Niño has not been investigated thus far. In the tropical Indian Ocean, the dominant interannual climate variability mode that can operate independently from ENSO is the Indian Ocean Dipole (IOD)35, which is manifested as an east-west dipole-like SSTA pattern, begins to develop in boreal summer and peaks in boreal fall.It has been recognized that inter-basin interactions among the three tropical ocean basins play a crucial role in shaping climate variability and long-term climate changeHere, we show observational evidence that positive phase of the IOD (pIOD) can cause westerly wind anomalies over the tropical Atlantic Ocean, weakening the easterly trade winds and causing warm SSTA. Consequently, the pIOD can trigger Atlantic Niño through atmospheric teleconnection. We confirm the associated physical mechanisms by performing various model experiments using standalone atmospheric and oceanic models, and fully coupled climate models.34. Similar SSTA regression patterns are obtained when the ENSO influence is removed , an index for the IOD defined as the difference of SSTA between western and eastern tropical Indian Oceanin Figs. . MeanwhiThese observational analyses suggest that the Atlantic warm SSTA peaks in 3–5 months after the pIOD peak Fig. , when th25.The generation of the Atlantic Niño by the pIOD is initiated by the westerly wind anomalies associated with atmospheric Rossby wave’s lower-level cyclones over the tropical Atlantic Ocean. The anomalous equatorial westerlies induce eastward oceanic currents Figs. , d, adve41. In addition, the equatorial westerly wind anomalies may also contribute to the enhanced coastal warm SSTA through the downwelling equatorial Kelvin waves discussed above and the subsequent poleward-propagating coastally-trapped waves along the eastern boundary  experiments forced with the tropical Indian Ocean SSTA associated with the IOD. The AGCM results show that the pIOD indeed induces prominent westerly wind anomalies over the equatorial Atlantic Ocean during its developing and peak phases Fig. , b. Expe1, plays a crucial role in the growth of the Atlantic Niño to its mature stage, we further performed pacemaker experiments using a coupled climate model, in which the Indian Ocean SSTA is nudged to the observed values whereas atmosphere and ocean are fully coupled elsewhere  Atlantic Niño (Niña) events from 1950 to 2019, 10 (10) were preceded by positive (negative) IOD events, and the composited SSTA evolution resembles that of the regression pattern on the DMI Fig. . Similar22 or late-onset Atlantic Niño21, are associated with the pIOD forcing  twentieth-century reanalysis (ERA-20C)58, and sea level data during 1958–2017 from ECMWF Ocean Reanalysis System 4 (ORAS4)59. For comparison, we also analyze satellite-derived daily sea level data during 1993–2019 obtained from Copernicus Marine Environment Monitoring Service (CMEMS), and we remove the first three harmonics of daily climatology to obtain daily anomalies. To analyze the physical causes for the SSTA, we use surface heat flux data from ERA-20C.In order to examine large-scale climate anomalies associated with tropical climate modes, we analyze SST data during 1950–2019 from the Hadley Centre Sea Ice and SST (HadISST)34, defined as differences of SSTA averaged over the western  and eastern  tropical Indian Ocean. For the Atlantic Niño, we use the SSTA averaged over the ATL3 region . In this study, we define positive IOD (pIOD) events as when the peak of 3-month smoothed DMI exceed its standard deviation, and negative IOD (nIOD) events as when the smoothed DMI falls below negative standard deviation. Similarly, Atlantic Niño events are defined as when the peak of the 3-month smoothed ATL3 index exceeds the one standard deviation threshold. Based on these criteria, we have selected 31 Atlantic Niño and 30 Atlantic Niña events during 1950–2019. Furthermore, if an observed Atlantic Niño is preceded by a pIOD within 5 months prior to its peak, the Atlantic Niño is considered associated with pIOD forcing, and similarly for observed Atlantic Niña and nIOD. We have selected 10 such Atlantic Niño events (32%), and 10 Atlantic Niña events associated with nIOD (33%) in observations . For the IOD, we use the Dipole Mode Index (DMI)To remove the influences of anthropogenic global warming, we remove the linear trend in all monthly climate variable anomalies. To exclude the ENSO-related signals  and future projections (2006–2019) from the forty-member ensemble of National Center for Atmospheric Research (NCAR) Community Earth System Model version 1 (CESM1) large ensemble (CESM1-LE)60 from Max Planck Institute (MPI) in Hamburg (HAM). Model horizontal resolution is ~2.8°, with 19 vertical levels. We performed two sets of AGCM experiments, forced by positive and negative IOD SSTA in the tropical Indian Ocean, respectively. Outside the tropical Indian Ocean, SST is set to monthly climatology. The SSTA forcing was obtained by computing the composite of observed IOD events for both the developing and decaying years. The model was integrated for 42 years, and the first 4 years were discarded given that it takes a few years to reach the model equilibrium state. Since the SSTA forcing has a 2-year period, i.e., the developing and decaying years of the IOD, we have 19 ensemble members available for analysis.To further confirm our proposed mechanism that the IOD affects the tropical Atlantic wind anomalies through the atmospheric bridge, we perform atmospheric general circulation model (AGCM) experiments using ECHAM4.662 to examine the impact of wind anomalies induced by the IOD on the tropical Atlantic Ocean. The ocean model was forced by differences of surface wind stress anomalies during June–November between the two sets of AGCM experiments. It has 25 baroclinic modes, and a horizontal resolution of 0.5°. The model experiment started from a state of rest with a realistic background stratification and a flat ocean bottom with a depth of 4000 m. It was spun up for 5 years, and integrated forward for another 5 years, which are analyzed in this study.We also used a linear ocean modelGiven that local air-sea interaction plays a crucial role in the formation of the Atlantic Niño, we further performed pacemaker experiment using the NCAR CESM1, in which we restored the Indian Ocean SSTA to observed values (Supplementary Fig. Supplementary InformationPeer Review File


We also find thatexciton transport in the 21Ag– state occurs without exciton–exciton annihilation. Both 21Ag– and 11Bu+ states are found to exhibit subdiffusive behavior. Abinitio GW-BSE calculations reveal that this is dueto the comparable strengths of the exciton–phonon interactionand exciton coupling. Our results demonstrate the link between electronicstate symmetry, backbone torsion and phonons in exciton transportin π-conjugated polymers.Many optoelectronicdevices based on organic materials requirerapid and long-range singlet exciton transport. Key factors controllingexciton transport include material structure, exciton–phononcoupling and electronic state symmetry. Here, we employ femtosecondtransient absorption microscopy to study the influence of these parameters on exciton transport inone-dimensional conjugated polymers. We find that excitons with 2 Here, the electronic ground state (S0) exhibits11Ag+ symmetry. Depending on thepolymer conjugation length and backbone geometry the first (S1) and second (S2) excited electronic states areeither of 21Ag– or 11Bu+ symmetry.5 Irrespectiveof the exact state ordering, photoexcitations in conjugated polymersrapidly form excitons in the lowest energy excited S1 state.When the S1 state is of 21Ag– symmetry the materials are typically nonfluorescent,the S1 state supports some triplet-pair character 1(TT)8 and frequently shows a short electronic lifetime.On-the-other hand polymers with an S1 state of 11Bu+ character are often luminescent with longelectronic lifetimes.10Organic optoelectronicdevices ranging from light-emitting diodesto photovoltaic cells and transistors15 the impact of the electronic symmetry of the S1 stateon exciton diffusion behavior remains largely unexplored. In otherwords, it is not known whether a 21Ag– or 11Bu+ symmetry state would providebetter exciton transport properties. At first glance it might appearthat the longer lifetimes of 11Bu+ states would enable longer exciton diffusion lengths. But the significantlyaltered electronic structure and many-body character of 21Ag– states may provide access to uniquediffusion properties. The experimental study of exciton diffusionin molecular systems is challenging due to the difficulties associatedwith measuring ultrafast, nanoscale exciton diffusion properties insystems that exhibit sub-100 ps electronic lifetimes coupled withsub-100 nm exciton diffusion lengths.13 Criticallychallenges associated with systematically tuning polymer electronicstructure without introducing detrimental effects such as interchaindisorder, cross-linking, etc. have until now prevented a systematicinvestigation of electronic symmetry on exciton diffusion.Despite our considerableunderstanding of the electronic structureof conjugated polymers,19 to measure exciton transportin different topochemically  polymerized polydiacetylene (PDA) chains.PDAs offer an ideal platform to study the effect of electronic propertieson exciton transport for several key reasons. Structurally, PDAs consistof extended (2–5 μm) one-dimensional polymer chains thatare distinguished by the degree of backbone torsion. Perfectly planarpolymer chains are typically referred to as “blue” PDA,while polymer chains with a defined backbone torsional angle (40°)are known as “red” PDA. We note that although the “blue”PDA actually has redder absorption peaks than the “red”PDA, the naming convention is historical and based on the color ofthe crystals.20 In this study the chainsare dilutely (polymer content 10–4–10–3w/w) and homogeneously distributed (50–100nm separation) in a ∼500 nm thick crystal of their monomer;the size of the domains within the macroscopic crystal are ∼20μm2 (see Supporting Information (SI) Section S1). We refer to these samples henceforth as (thin)films. PDAs have found widespread use in a range of optoelectronicapplications such as temperature sensors,21 lithographic resists,22 dye sensitizedsolar cells,23 photoelectric devices24 and transistors. Although PDA has found lessuse than other conjugated polymer systems such as P3HT or polyfluorenethe absence of significant interchain disorder, cross-linking, andintegration into nanostructures allows the theoretical propertiesof correlated 1D electronic systems to be tested in the idealized polymer limit in PDA, as such it is a model system to investigateexciton transport in polymer systems. The electronic structure ofPDAs are very similar to other modern conjugated polymers such aspolyacenes, iso-indigo-based polymers,25 carotenoids26 and singlet-fissionmaterials making the results here applicable to many other systems.The torsional backbone angle is controlled by the side-chains of thediacetylene monomer and exact synthetic preparation method as shownin a previous study.27 Other than the backbonetorsion both PDAs show near-identical structural and chemical materialproperties, that is, degrees of polymer content, polymer alignment,structural disorder, etc. . Electronically, both PDA phases display strong coupling betweenthe monomer units and exhibit large exciton coherence lengths.29 Owing to the planar backbone geometry, “blue”PDA exhibits an optically accessible 11Bu+(S2) which lies above a 21Ag–(S1) state. This ordering gives riseto a broad visible absorption spectrum dominated by vibrational progressionsat 1400–1500 and 2100 cm–1  state lying above the optically accessible 11Bu+(S1) state. As a consequence, “red”PDA exhibits a significantly blue-shifted absorption spectrum comparedto “blue” PDA  wefind that the SE (11Bu+) decays monoexponentiallyto the ground state with a lifetime of 630 ± 10 fs, while thePIA at 750–900 nm decays with a lifetime 1300 ± 40 fsand the PIA at 680–700 nm with 2300 ± 130 fs. The observedexcited-state features and dynamics agree excellently with previousreports.32 Followingthis agreement, we can assign the SE band to 11Bu+ (S2), the broad PIA is attributed to the21Ag–(S1) stateand the narrow PIA at 680–700 nm to a hot, vibrationally excited,ground state.34 Photoexcitation of “blue” PDA to 11Bu+ (S2) is thus followedby rapid internal conversion within 90 fs to 21Ag–(S1)  which decays back to theground state. In “red” PDA the transient absorptionspectrum shows a single broad PIA in the 650–900 nm range.The decay of this PIA is 13.8 ± 0.2 ps and has been suggestedto correspond to the transition between 11Bu+(which is theS1 state in this system) anda state lying at ∼3–3.5 eV, of nAg or charge transfer (CT) character.27 Weemphasize that we carried out both fs-TA  as a function of carrier density (excitations per unitlength of polymer chain (n0) in a rangefrom n0 = 0.1–2 nm–1; SI Section S4). In both cases theseresults showed that for “blue” PDA the kinetics do notvary with carrier concentration whereas annihilation was observedfor “red” PDA.The ensemble excited state properties of “blue” and“red” PDA films following photoexcitation with a 10fs pump pulse centered at 560 nm35 In fs-TAM a pump pulse is focused via a high-numerical aperture(NA = 1.1) objective to near the diffraction limit Gaussian spot (σ= 143 nm), which locally creates excitons within the sample. Aftera variable time delay, a broadband, 7 fs probe pulse centered at 780nm is loosely focused on the sample to image the pump-induced signalchanges in the material. The transmitted probe is subsequently imagedonto a two-dimensional detector. By recording the transmission imagewith and without the pump pulse incident on the sample, we calculatedthe spatially resolved transient absorption image of the locally excitedexciton distribution as a function of pump–probe time delay.Tracking the temporal evolution then allows us to extract informationabout exciton diffusion properties. For “blue” PDA weprobed in the center of the 21Ag– PIA band at 800 nm  with a similar 10 fs pump pulse centeredat 560 nm.SI Section S3).We subsequently computed the mean-square-displacement (MSD) for theunderlying spatial exciton profile, which is a measure of the changein the spatial extent of the exciton population as a function of time.Fitting is performed with a 2D Gaussian as opposed to Bessel function(which results from the far-field radiation pattern of a transmittedplane-wave probe). This is due to the computational complexity associatedwith the latter and the fact that fitting with a 2D Gaussian showsthat the diffraction rings are reproduced faithfully. This impliesthat the deviation from a true two-dimensional spatial profile inour measurements, due to the diffraction ring, has no effect on theretrieved spatial standard deviation (see SI Section S3). As shown in SI Section S3). This behavioris expected based on the one-dimensional structure of PDA and thelow polymer content (10–4 – 10–3w/w) of the samples remains, preventing interchain transport. Severalchains will be excited by the pump pulse with the pump probe signaltaken as the average of all chains within the exciting spot. Our resultstherefore suggest that exciton propagation proceeds along the long-axisof the PDA chains .27 We remark that varying the probe wavelength within the broad PIAdid not alter the observed transport behavior .To quantify the spatialextent of the signal, we extracted thespatial standard deviation for all transient absorption images usinga 2D Gaussian fit  is the electronicpopulation at a time t and position x, D is the diffusion coefficient, τis the electronic lifetime and γ is a coefficient which accountsfor exciton–exciton annihilation. In the absence of excitonannihilation this equation can be solved to show that in one dimension,A is proportionalityfactor and α accounts for nonlinearity in time. In the caseof α = 1 we retrieve normal diffusion, whereas α >1 isknown as superdiffusive behavior and α < 1 is referred toas subdiffusive behavior. In this latter case a time-dependent diffusivity D(t) can be defined as,D and γ36 (see SI Section S3 for further details). We emphasize that in the data shown in A salient feature of the MSD curves displayed in 1Bu+ compared to 21Ag– excitons is an important observationthat is not well understood. While beyond the scope of this article,we note that the 21Ag– stateexhibits a lower transition dipole moment than 11Bu+ 7,.37 Giventhat the annihilation cross-section of a state is proportional toits transition dipole moment40 this may explain why the 21Ag– symmetry excitons do notexhibit significant annihilation effects.41 A similar effect has been observed in H- and J-aggregate systems.In the former, where S1 is dark, the phase relationshipbetween two dipoles leads to destructive interference and suppressedannihilation, whereas in J-aggregates where S1 is brightthe opposite occurs.43 The 21Ag– excitons can still scatter in such a way that would lead to annihilation, but this would require theexcitons to be very close, or at high densities. We note that it ispossible that local geometry/structure around the excitons preventsthem from approaching each other, and that the excitation densitydoes not reach the magnitudes required for short-range annihilationmechanisms to be operative .Computing the interexciton separation (at the highest excitation densitiesused in the study) shows that excitons remain separated by at least1 monomer unit in both “blue” and “red”PDA suggesting Auger and impact ionization events can indeed be ignored(see SI Section S5). Other effects suchas disorder or local microstructure may in addition to the symmetryof S1 play a role in suppressing annihilation in “blue”PDA. Study of other polyene systems such as carotenoids which havebeen shown to have similar dynamics to PDA,31 may aid this, however independently investigating the effects ofsymmetry remains challenging.To identify, which model shouldbe applied, we carried out a fluencedependence on the same sample spot for both PDAs, as shown in D, and annihilation parameter,γ for “red”PDA. In contrast, for “blue” PDA we fit A and α and then extract the diffusion coefficientfrom the time-dependent diffusivity D(t) according to 2 s–1 for “blue”PDA ), which is significantlylarger and more varying across different sample locations as comparedto “red” PDA with 7 ± 6 cm2 s–1. We remark that the spread in diffusion coefficients for “blue”PDA is larger than for “red”, however further studiesare required to ascertain the origin of such behavior. The exponentvalue, α, for “blue” PDA lies between 0.7–0.9and indicates subdiffusive exciton transport. For “red”PDA the annihilation coefficient, γ, ranged between 0.1–1.1cm s–0.5 (SI Section S5). The units of cm s–0.5 reflect the one-dimensionalnature of polymer. The annihilation coefficient, like the diffusioncoefficient, will be time dependent, however is found not to varyin the time range studied here nor is found to vary significantlywith sample location (SI Section S5). Wenote that to obtain D for “red” PDAthe fluence dependent traces were fit independently. The data in –0.5.Based on the observed power dependence,we applied SI Section S5). This suggeststhat the annihilation is still only a minor contributor to the subdiffusivetransport.44 In comparison to other conjugatedpolymer systems the annihilation coefficient in “red”PDA is around 10 times lower, for example, as compared to polyfluorene45 where γ was measured to be ∼3 cms–0.5. However, γ is also 2–3 ordersof magnitude larger than in these systems1 and more comparable to that observed in 2D TMDC materials such asMoS2,46 black phosphorus47 and 2D perovskites.48 Comparison of absolute values should, however, be performed withcare due to the time dependent nature of the diffusion coefficientand the difference in dimensionality between these systems. At earlytimes (sub-1 ps) γ will be higher due to the radiative decayof excitons, the t–1/2 dependenceof the annihilation parameter and static annihilation; we do not considerthis latter contribution at the fluences used here in-line with otherstudies.45 We note for “red”PDA, the diffusion coefficients extracted in n0 (carriersper unit length of polymer) ∼ 0.1 nm–1).Critically, while this annihilation factor is substantial,theratio of the first and third term in τelec is the intrinsic lifetimeof the underlying process. Previouslywe have determined for 21Ag–, τelec is ∼600 fs, whereas for 11Bu+,τ ∼ 9000 fs.31 Based on these values we can extract diffusion lengthsof 26 ± 6 nm and 33 ± 5 nm, for “blue” and“red” PDA, respectively. It is noteworthy to mentionthat the diffusion length is similar for both systems, despite theirstark difference in diffusion coefficient and annihilation characteristics.Long-range exciton transport thus requires not only highly mobileexcitons with minimized annihilation, but also long state lifetimes.We re-emphasize at the polymer concentrations used here, the PDA chainsdo not interact, with the separation between chains (∼100 nm)being larger than the exciton diffusion length. Indeed, several studieshave shown that interchain hopping and the formation of interchaincharge transfer states does not occur in PDA.50 In a previous study it was also shown that exciting at the band-edgeof PDA, whose band-edge absorption is dominated by partially polymerizedstates, does not show any new spectroscopic signatures or electroniclifetime changes.31 This again furthersthe conclusion that hopping between chains does not occur. Finally,the low temperature absorption line width of crystals studied hereis similar to that reported for isolated chains in previous studies(SI Section S1), this again suggests thatinterchain interactions are not significant.51 These observations further corroborate the claim that defect statesgenerally play little role in our observations here. Performing fs-TAMmeasurements on thicker PDA crystals which have a lower Urbach energy31 (30 meV versus 34 meV) shows that the diffusioncoefficient and dynamics remain qualitatively unchanged (SI Section S4). There is however a small difference(0.6–2 cm2 s–1) in the diffusioncoefficient between the thick and thin crystals which may be relatedto the ∼10% difference in electronic disorder; further studiesare needed to fully confirm this. We finally also note that PDA crystalswere masked under a polarized optical microscope prior to measurement(SI Section S1) to ensure excitation wasperformed away from grain boundaries which can be well resolved inthe materials. As such although the energetic disorder is larger than kBT in the materials our resultssuggests that trap states are not significant in our observationsor responsible for the difference in transport between “blue”and “red” PDA.Having discussed the origin of the observed exciton dynamics wecan determine the overall diffusion length from1Ag– and 11Bu+ states, which is typical of strong exciton–phononinteractions52 that lead to localized excitons.In order to understand these seemingly inconsistent observations,we employ ab initio GW-BSE calculations to quantifythe two competing effects. These calculations on the properties ofexcitons and exciton–phonon interactions have previously beensystematically tested on PDAs as a part of a separate study.53 The electronic coupling between excitons residingon neighboring monomers of the polymer chain (J-coupling)drives the system to a more delocalized state. From a calculationof the exciton bandwidth  we coulddetermine J = 0.54 eV for the 11Bu+ state of the planar (“blue”) PDA.Unfortunately, the multiexcitonic character of the 21Ag– state prevents us from obtaining the corresponding J value within GW-BSE, which is a methodologybased on Green’s functions that only captures single excitations54 and cannot describe biexcitons.55 Extending this formalism to describe excited states involvingmore than two particles is an active field of research and beyondthe scope of this work. Nevertheless, the larger diffusion coefficientof the 21Ag– state makes itlikely that it will have a value of J that is greaterthan 0.54 eV. The 11Bu+ state ofthe “red” PDA will have a smaller excitonic couplingcompared to the same state in the “blue” phase due tothe decreased p-orbital overlap that the torsion θ between subsequentmonomers induces, and in particular a simple estimate of its valueis J·cos θ = 0.41 eV. We note that whilethe 21Ag– state has been shownto possess 1(TT) character, no free triplets31 have been observed to form in the specific typeof red or blue PDA crystals studied here, hence we do not considertheir contribution here. This in accordance with the low triplet yieldvia singlet fission in PDA56 and the generally lowintersystem crossing yields in conjugated polymers.57 This in agreement with the significantly lower diffusioncoefficient reported for triplet excitons59 (2–3 orders of magnitude lower than observed here for singlets)and predictions of a lower J coupling.55Despite the high diffusion coefficientsobtained at room temperaturein these systems 2, which 1Bu+ state of PDA to be λ = 0.43 eV (SI Section S7), which denotes the driving forceof the system to localize after photoexcitation. The carbon–carbondouble- and triple-bond stretch have the largest contribution to thereorganization energy , resulting in the prominent vibronic progressionof the absorption spectrum of 60 Indeed, the exciton wave function is significantly affectedwhen these vibrations are displaced compared to other motions, asshown in SI Figure S6. Moreover, phononsare known to lead to a renormalization of exciton properties comparedto a “static” picture.61 Inorder to quantify the vibrationally induced renormalization of propertiesrelevant to exciton diffusion in PDA we employ a quadratic approximation(SI Section S7), which allows us to identifythe effect of the individual phonon modes. We find that phonons atroom temperature only lead to a small increase of the exciton energyby 15 meV, and a small decrease of the excitonic coupling by 5 meV.However, we find that the magnitude of the exciton transition dipolemoment undergoes a more significant renormalization due to the effectof phonons, from a value of 1.82 au to 1.30 au, and it is mainly thecarbon–carbon double- and triple-bond stretching motions thatdrive this effect (SI Table S3). This reductionin the magnitude of the transition dipole moment |μ| results in reduced exciton–exciton annihilation, since thecross-section of this process is proportional to |μ| as already discussed previously. Hence phonons appear to quenchthe competing to exciton diffusion effect of exciton–excitonannihilation.Moreover, we quantify the strength of exciton–phononcouplingby calculating the reorganization energy of the 1J-couplingstrength, we can now classify the transport regime in which PDAs operate.If J-coupling is small compared to the reorganizationenergy, we anticipate the system to localize on a single monomer andtransport will only occur via incoherent hopping. Conversely, in ourPDA films, we calculated, J ∼ λ. Thissuggests that exciton transport may operate in the coherent regimewhere exciton delocalization is dominant.63 However, the similarity between J and λ alsosuggests that exciton localization via exciton–phonon couplingscan still occur. The subtle interplay between exciton–phononcoupling  and J-coupling demonstrates that exciton transport occurs through the motion of partiallydelocalized excitons that reside on several monomers. This leads tosubdiffusive exciton transport with high diffusion coefficients. Weexpect this conclusion to carry to the 21Ag– state, since the J coupling of thisstate is likely larger than that of 11Bu+, as its experimentally measured more rapid delocalizationsuggests. Moreover, increasing exciton delocalization has been shownto lead to reduced coupling to high-frequency phonons in organic materials.61 Since the reorganization energy is dominatedby the contribution of such high-frequency modes (SI Table S2), we expect its value to be smaller for the 21Ag– compared to the 11Bu+ state, and for the criterion J > λ that defines coherent transport to still hold.Based on the reorganization energy and 1Ag– excitons have on average∼3 times higher diffusion coefficients than 11Bu+ excitons in PDA polymer chains. Where the excitontransport of 11Bu+ excitons exhibitsannihilation effects, for 21Ag– excitons, the smaller transition dipole moment likely results inno measurable annihilation. The motion of both 21Ag– and 11Bu+ excitons however appears to remain subdiffusive likely due to exciton–phononmediated trapping effects. Despite its smaller diffusion coefficient,the longer electronic lifetime of 11Bu+ means that 21Ag– and 11Bu+ excitons have a similar diffusionlength (∼30 nm). Our results suggest that 21Ag– excitons are able to move across spaceas effectively as excitations that live orders of magnitude longer.This is in part due to the absence of annihilation losses.In summary we have investigated the influence of electronic statesymmetry on exciton diffusion in conjugated polymers. We have shown21Ag–, suchthat a simple band picture with different hopping matrix elementscannot explain all of our observations. Indeed, it is not obviousthat the dispersion (which will determine the group velocity and laterthe diffusion rates) is necessarily larger in the “blue”PDA, compared to the “red”. For example, if 21Ag– has a strong triplet-pair contribution,as some studies have suggested, one might even imagine that the excitationwould spread more slowly, even though the monomers have stronger electroniccoupling.Thepolymer backbone geometry will also play a role, that is, “blue”PDA is planar, whereas the “red” PDA is twisted. Thiswill also influence coupling across monomers along the chain via orbitaloverlap and the extent of exciton delocalization. However, these effectsmust be combined with electronic correlation phenomena, such as theformation of the 21 shouldbe considered when designing new conjugated polymers for exciton transportboth in terms of annihilation and diffusion properties. Our resultsdescribing the interplay of electron–phonon coupling and J-coupling suggest that careful consideration of bondingmotifs should be taken such that the contribution of both to transportcan be optimized. Finally, although PDA has not found as widespreadused in organic electronics as other semiconducting polymers our resultswith high diffusion coefficients call for a renewed interest in thematerial.In terms of design rules for organic electronics ourresults highlighta number of key principles. First, even in highly ordered systemsintroducing a small amounts of electronic disorder can potentiallyaffect the transport behavior as evidenced by measurements on PDAcrystals of different thickness. Additionally, the results suggestthat not only delocalization (via the backbone twist angle) is importantin enhancing exciton diffusion but the symmetry of Sn-butoxy-carbonylmethyl-urethane)diacetylene moleculeswere synthesized in-house using the method previously outlined bySe et al. and references therein.64 Thesynthesis classically consisted of two steps: (i) oxidative couplingof 4-pentyn-1-ol (Hay’s method) to produce the 4,6-decadiyn-1,10-dioland then, (ii) reaction of the diol with n-butylisocyanateacetate. Note that the source 4-pentyn-1-ol was not synthesized atthe laboratory but purchased from Sigma-Aldrich (Merck). Ultrathinsingle crystals were grown between two coverslips using a melt-processingmethod. The whole process was systematically carried out under a polarizedoptical microscope so as to be able to follow and control the sampleelaboration: a very small amount of diacetylene powder is placed atone edge of the double-slides assembly; when heating above the meltingtemperature (∼65 °C) the liquid diacetylene fills theempty space by capillary action to form a thin liquid film betweenthe two substrates. Rapid cooling leads to the formation of a highlypolycrystalline film. The sample is then heated again to around themelting temperature until the melting of all the crystallites tookplace. When only a few crystal germs remain the sample is cooled againat a very slow cooling rate  to inducethe growth of large single monocrystalline domains from the germs.Typical polymer contents by weight are then in the 10–4–10–3 range. The interchain separation  is obtained from the absorption opticaldensity (OD) and Beer Law, where 6 cm–1 20 for light polarizedparallel to the long axis of the chains and l  is ∼500 nm. The spatial separationbetween chains is assumed to be significantly large enough that thereare negligible interchain interactions. X-ray diffraction31 and microscopic optical transmission measurements(SI Section S1) also confirm that chainsremain linear and highly aligned over macroscopic length scales, againsuggesting that interchain interactions can be ignored.3BCMU (3-methyl-2) diacetylene were grown before being slightly polymerized.Large size crystalline regions (∼mm2) with submicronicthicknesses (∼100–200 nm) are obtained using a meltprocessing method.65 A few mg of the purifieddiacetylene powder are melt (T ≥ 80 °C)and the liquid is injected, using capillarity action, in the spacebetween two superimposed microscope coverslips. After rapid coolingthe thin liquid film crystallization leads to the formation of a highlypolycrystalline structure, being the assembly of microdomains. Thesample is then heated again under a polarized optical microscope untilalmost all the melting takes place but preserving a few single crystalgerms. At that point the sample is cooled again at a very slow coolingrate to induce the growth of hundreds of μm–mm scaledomains from the germs until room temperature is reached. The (3Nφ2) is a highly stable monomer that is characterized by bothweak thermal- and weak UV photo- reactivity.27 Polymer chains are thus generated by exposure to X-ray light ina diffractometer . The polymer content is adjustedby trial and error and kept low enough to form a solid solution of isolated polydiacetylene chains insidetheir diacetylene host crystal.To make multipulsesmicroscopy possible by limiting scattering of the pump pulse ultrathincrystalline monodomains of the  into a 4 mm YAG crystal. The resultingabsorption (corrected for the sample substrate) was then collectedby imaging with a Silicon photodiode array camera .–1 mode could be resolved. The probe white light was delayed usinga computer-controlled piezoelectric translation stage (Physik Instrumente),and a sequence of probe pulses with and without pump was generatedusing a chopper wheel (Thorlabs) on the pump beam. The pump irradiancewas set to a maximum of 38 μJ/cm2. After the sample,the probe pulse was split with a 950 nm dichroic mirror (Thorlabs).The visible part (520–950 nm) was then imaged with a Siliconphotodiode array camera . The near-infrared part was imagedusing an InGaAs photodiode array camera . Measurements were carried out with a time step sizeof 4 fs out to 2 ps to minimize the exposure time of the sample tothe beam. Unless otherwise stated, all measurements were carried outwith the probe polarization set parallel with respect to that of thepump  and along the PDA chains. Theabsorption spectrum of samples was measured after each pump–probesweep to account for any sample degradation.The fs-TAexperiments were performed using a Yb-based amplified system  providing 14.5 W at 1030 nm and 38 kHz repetitionrate. The probe beam was generated by focusing a portion of the fundamentalin a 4 mm YAG substrate and spanned from 520 to 1400 nm. The pumppulses were generated in home-built noncollinear optical parametricamplifiers (NOPAs). The NOPAs output (∼4 to 5 mW) was centeredtypically between 520 and 560 nm (fwhm ∼65–80 nm), andpulses were compressed using a chirped mirror and wedge prism (Layerterc)combination to a temporal duration of ∼9 fs. Compression wasdetermined by second-harmonic generation frequency-resolved opticalgating  and further confirmed by referencemeasurements on acetonitrile where the 2200 cm35 Briefly, a Yb:KGW amplifier system was usedto seed two white-light stages for pump and probe generation. Thepump white-light (3 mm Sapphire) was spectrally adjusted with a 650nm short-pass filter , and compressed to 10 fsfor all optical elements with two pairs of third-order compensatedchirped mirrors and a wedge-prism pair (Layertec). Subsequently, themode of the pump pulse is cleaned by a pinhole before being focusedthrough the objective lens  to a spot sizeof ∼340 nm . The probe white-light(3 mm YAG) was spectrally adjusted to 650–900 nm in a home-buildfused silica prism filter and compressed to 7 fs with a pair of third-ordercompensated chirped mirrors and a wedge-prism pair (Venteon) beforebeing free-space focused onto the sample . The transmitted probe was imaged ontoan emCCD  at 55.5 nm/pixel as verifiedby a resolution target. The frame rate of the camera was set to 30Hz with an integration time of 11 ms and pump off/on images were generatedby a mechanical chopper at a frequency of 15 Hz. For the measurements,we adjusted the pump fluence to achieve initial concentration of carriersper unit length of polymer (n0) in therange: n0 = 0.1–2 nm–1 for all samples.The femtosecondwide-field detected transient absorption microscope has been describedin detail previously.


Recently, explicit spin selection was described as a possible way to promote OER in alkaline conditions, but the specific spin-polarized kinetics remains unclear. Here, we report that by using ferromagnetic ordered catalysts as the spin polarizer for spin selection under a constant magnetic field, the OER can be enhanced. However, it does not applicable to non-ferromagnetic catalysts. We found that the spin polarization occurs at the first electron transfer step in OER, where coherent spin exchange happens between the ferromagnetic catalyst and the adsorbed oxygen species with fast kinetics, under the principle of spin angular momentum conservation. In the next three electron transfer steps, as the adsorbed O species adopt fixed spin direction, the OER electrons need to follow the Hund rule and Pauling exclusion principle, thus to carry out spin polarization spontaneously and finally lead to the generation of triplet state O2. Here, we showcase spin-polarized kinetics of oxygen evolution reaction, which gives references in the understanding and design of spin-dependent catalysts.The oxygen evolution reaction (OER) is the bottleneck that limits the energy efficiency of water-splitting. The process involves four electrons’ transfer and the generation of triplet state O Here, authors demonstrate the ferromagnetic catalyst to facilitate spin polarization in water oxidation reaction. They find the ferromagnetic-exchange-like behaviour between the ferromagnetic catalyst and the adsorbed oxygen species. Non-precious 3d-transition metal oxides (TMOs), such as Fe-, Co-, and Ni-based oxides, are promising cost-effective catalysts.7 Their catalytical activities are tunable as the diversity in oxides families affords numerous freedoms to tailor their physicochemical properties. Sabatier’s principle, which qualitatively describes that the optimized catalytic activity when adsorbed species bind to the catalytic surface neither too strongly nor too weakly, led to the fundamental understanding of OER mechanisms and guided the subsequent design of highly active catalysts.9 This principle was further supported by the findings that the OER activities of transition metal oxides correlate strongly with the eg occupancy, which is related to the binding strength between the metal and the oxygen species.12 Some exceptions have been found not well fitted with the eg theory, which is partially resulted by the diverse and complicated magnetism in TMOs family.16 Besides, the produced O2 is in triplet ground state, where the frontier π* orbitals are occupied by two electrons with parallel alignment. In contrast, the ground spin state of reactant OH-/H2O is singlet with all paired electrons.18 The singlet states of the oxygen molecule were reported at an energy level of at least ~1 eV higher than its triplet state.19 Thus, the magnetism of TMOs, related to the spin polarization, should be influential on the kinetics of OER.21 It is reasonable to consider that the active sites with suitable thermodynamic paths for OER should allow a way to facilitate the spin alignment in the product. As suggested by recent theoretical studies by J. Gracia,24 the spin-polarized electrons in catalysts promote the generation of parallel spin aligned oxygen by quantum spin-exchange interactions (QSEI), which further promote the OER kinetics. Therefore, facilitating the spin polarization should be an effective strategy for improving OER efficiency. Ron Naaman and co-works reported that the application of the chiral-induced spin selectivity effect to product the polarized electron. This spin polarization transferred is the origin of a more efficient oxidation process in which oxygen is formed in its triplet ground state.27 It has been pointed out by J. Gracia et al. that theoretically photosystem II can act as a spin-controlling gate to govern the charge and spin transport during the OER process,28 which offers a favoured thermodynamic path for O2 evolution. Besides the extrinsic spin polarizer, the ordered magnetic moment structure in ferromagnetic materials can create intrinsic spin filtering for highly spin-polarized electrons. The spin filtering effect originates from the exchange splitting of the energy levels in the conduction band of a magnetic insulator.29 Most recently, José Ramón Galán-Mascarós et al. reported an external magnetic field, applied by a permanent magnet, enhances the OER activity of magnetic oxides in alkaline.30 It opens a new strategy to manipulate the spin polarization in magnetic oxide catalysts for promoting the OER and encourages more detailed studies to understand how the magnetic field induced spin polarization affects the OER process.The sluggish kinetics of oxygen evolution reaction (OER) is a major cause for the low efficiency in techniques, such as solar water splitting,2O4 catalyst under the magnetic field. The ferromagnetic CoFe2O4 catalyst works as a spin polarizer under the magnetic field. We have found that the spin-polarized kinetics of OER starts at the first electron transfer step, where ferromagnetic exchange happens between the ferromagnetic catalysts and the adsorbed oxygen species (reactants) under the principle of spin angular momentum conservation. Without the magnetic field, the Tafel slope of CoFe2O4 is identical and equal to circa 120 mV/decade, which indicates the first electron transfer step is rate-determining step (RDS) and no electron transfer occurring before the RDS. Under the magnetic field, the Tafel slope decreases to circa 90 mV/decade, indicating the number of electron transfer is ~0.5 and a mixed RDS involving the first electron transfer step and second steps. Such a phenomenon cannot be observed in the catalysts without ferromagnetic orderings under the same condition. The results indicate that the key step of spin-polarized OER is the first electron transfer step in OER, where the spin-polarized process via exchange hopping can be facilitated under the magnetic field. As a consequence, the first electron transfer is no longer the RDS. After a facilitated spin-polarized ferromagnetic exchange of electrons, the adsorbed O species will overall settle on the fixed spin direction. Due to the Hund Rule and Pauli Exclusion Principle, the follow-up electrons’ transfer needs to carry out spin polarization spontaneously and finally lead to the generation of triplet state oxygen. Overall, we showcase the key kinetics information in OER under a magnetic field, which influences the micro- and macroscopic spin polarization and spin transport. This finding will be helpful for further development of magnetic field assisted OER-enhancing strategy and related catalysts.In this work, we report an investigation on the key kinetics change on the ferromagnetic CoFe2O4, Co3O4, and IrO2. The study will determine the suitable magnetic field and weather a global aligned magnetic moment can be achieved. The study of magnetic property reveals the optimal strength of the applied magnetic field for the alignment of the magnetic moment in ferromagnetic CoFe2O4. The CoFe2O4 and Co3O4 were prepared by a modified solid-state chemistry method as previously reported.11 X-ray powder diffraction characterization was performed to confirm their crystal structures. The diffraction patterns match well with the standard patterns without impurity peak found  of 44 emu·g−1. The Co3O4 and IrO2 samples with tiny susceptibility (χ) of 3.07 × 10−5 and 0.51 × 10−6, respectively, at 300 K show antiferromagnetic or paramagnetic behaviors, respectively. The detailed magnetic data are summarized in Supplementary Table 2O4 is promoted obviously under the magnetic field while the changes in non-ferromagnetic catalysts Co3O4 and IrO2 are negligible. When a strong enough magnetic field (higher than the coercivity) is applied to a ferromagnetic material, the magnetic moment will  align along with the direction of the external magnetic field. The ferromagnetic (long-) ordered material as spin polarizer is an extended selective spin-filter for electron transfer during catalysis. The generation process of polarized electrons has been illustrated in Fig. We begin with the discussion of the magnetic properties of the employed catalysts, CoFe36 in which the mass transport in the electrochemical process was found to be affected by the Lorentzian movement, i.e. the diffusion of regents and the release of the generated gas bubbles are promoted. However, in this study, some evidence has excluded such effect from mass transport as a main contributor to OER enhancement under the magnetic field. First, the improvement was not observed on non-ferromagnetic catalysts Co3O4 and IrO2 with the effect of Lorentzian movement on mass transport. Second, we also tested the OER performance of Co(acac)2 and Fe(acac)3 with and without a constant magnetic field  with 500 S/m as a conductive mediator is mixed with those oxide catalysts for their application as the electrode,43 which dominants the electron conduction.It should be noticed that the use of magnetic fields in water electrolysis has been studied in the past,46 In our case, there are no changes in OER performance of CoFe2O4 during CA tests in 1 M KOH for 1 h shown in Supplementary Fig. 2O4 is stable without noticed surface reconstruction during the OER process. The high-resolution transmission electron microscope (HRTEM) was further used to rule out the possible interference from surface reconstruction of catalysts during the OER. It has been found that the spinel crystal structure of CoFe2O4 remained after the electrochemical treatment , no changes in the vibrational modes were observed, which proves once again that there is no surface reconstruction in OER. X-ray photoelectron spectroscopy (XPS) was also performed to study the surface chemical states of CoFe2O4 before and after the OER. As shown in Supplementary Fig. p orbital of Fe, Co, and 1 s orbital of O. The XPS of Fe 2p core level presents two pairs of peaks: Fe3+ 2p3/2 at about 710.7 eV and 713.2 eV; Fe3+ 2p1/2 at about 724.1 eV and 726.2 eV. The doublets in samples can be ascribed to Fe3+ in octahedral sites and Fe3+ in tetrahedral sites, respectively. The two peaks of Co 2p with the binding energy of 780.1 and 782.0 eV are ascribed to Co2+ ions in octahedral sites and Co2+ ions in tetrahedral sites. The main peaks of O 1 s at 529.6 eV are recognized as oxygen ions, which are all associated with a “−2” formal charge.49 Compared to the spectra before and after the OER, these peaks remain unchanged in location, indicating no surface reconstruction.It is generally recognized that some Co-based perovskites and spinels undergo operando surface reconstruction to form active Co (oxy) hydroxides in alkaline conditions to promote OER.ulk Fig. . The HADulk Fig. . Raman tα + n)F] .51 Ideally, the Tafel slope tells the information of reaction kinetics. For example, the Tafel slope is 120 mV·dec−1, which indicates the first electron transfer step is the RDS because there is no electron transfer before the RDS. If the second step is the RDS, the Tafel slope will decrease to 40 mV·dec−1 with an electron transfer number of 1. The change of the Tafel slope is often reputed as an indication of the change of reaction mechanism. As shown in Fig. 2O4 is about 109 ± 4.7 mV·dec−1 and that indicates the first electron transfer from the adsorbed OH− is the RDS without the magnetic field. But, after applying a constant magnetic field, the Tafel slope decreases to circa 87.8 ± 5.2 mV·dec−1, indicating the number of electron transfer is about 0.5 and a mixed RDS involving the first electron transfer step and second steps. Furthermore, we have carried out OER measurements of CoFe2O4, Co3O4, and IrO2 under different temperatures as shown in Fig. 52. More importantly, the OER performance of the ferromagnetic CoFe2O4 is promoted under the magnetic field at various temperature. However, the positive influence of the magnetic field on the OER performance of CoFe2O4 is decreased as the reaction temperature increases. The corresponding Tafel slopes are shown in Fig. 2O4 is about 106 mV·dec−1 without the magnetic field. After applying a constant field, the Tafel slope decreases to circa 82.8 mV·dec−1. As the temperature increases, the positive influence of the magnetic field became not that remarkable. This is because the arrangement of magnetic moments of catalyst will be thermally disturbed. The ferromagnetic ordering in the catalyst gets disturbed and thus a certain degree of demagnetization at high temperature occurs, which lead to the decreased influence of the magnetic field on OER. We also note that the Tafel slope of CoFe2O4 have a slight favorable change as temperature increases, which maybe because the interaction between two M-O unites mechanism occurs at high temperature.54 Thus, the key step in spin-polarized OER is the first electron transfer step in FM CoFe2O4, where the adsorbed OH− is difficult to deprotonate and transfer the electron. However, the change of Tafel slopes was not observed in the non-ferromagnetic catalysts under the same condition.Oxygen evolution reaction is authenticated a four-step reaction with each step accompanied by an electron transfer. The Tafel plots are widely regarded as a generalized kinetics theory for electron transfer reactions. The Tafel equation presents the relationship between the Tafel slope and the exchange current density:− and the active site. As revealed by our previous work, the octahedral sites are mainly responsible to the OER55. The extended X-ray absorption fine structure (EXAFS) showed the perfect inverse spinel structure of CoFe2O4  catalyst, the orbitals of the FM oxides create an intrinsically degenerate spin-polarized metallic state that optimizes the wavefunction based on the inter-atomic reduction of the electron–electron repulsion. DFT calculations were performed to explore the diffierent elctron structure of CoFe2O4 under an applied magnetic field  will happen , and the “first” electron transfer step is O* + OH− → *OOH + e−. The spin-related OER mechanisms show in Fig. 2O4 with FM ligand hole will form oxygen termination with fixed spin direction. The first electron transfer process led to the generation of O(↓)−, that is, the first electron transfer step is spin-polarization process to form the triplet state intermediate O(↓)O(↓)H species with a lower barrier  surface of CoFe2O4 with and without spin alignment. Please be noted that here the topmost layer of the slab model is fully relaxed in the calculations since there is little difference between the one-layer-relaxed model and the tww-layer-relaxed model, which can be also found in literature60 The calculation model of CoFe2O4 is shown in Supplementary Fig. 62 to produce triplet oxygen is shown in Fig. 59 and the overpotential of producing triplet oxygen is reduced by 390 mV compared to that without aligning spin. The coordinated inter-atomic aligned spin on active sites plays an important role in optimizing the spin-dependent reaction coordinates.The electron transfer at the catalytic interface depends on the transition probability, which is associated with the wavefunction integral between OH2O4 Fig. , there ioms Fig. . The cals on the 1 surface2 molecules starting from diamagnetic species (OH− and H2O). For a reaction involving non-magnetic molecules only, not impact significantly on the reaction kinetics. We investigated the methanol oxidation reaction (MOR) and ethylene glycol oxidation reaction (EGOR) on CoFe2O4 under the magnetic field. Here, changes in FM catalyst conductivity caused by magnetic fields can be ignored because that AB mediator is also mixed with CoFe2O4 for their application as the electrode, which dominant the electron conduction. Figure It is worth noting that OER requires the generation of paramagnetic O2O4  during OER. We have found that the Tafel slope of overall ferromagnetic CoFe2O4 switched from ~120 to ~90 mV·dec−1 after applying a magnetic field. It indicates the change of the RDS of OER reaction under an external magnetic field, i.e. the first electron transfer step is no longer the RDS. The spin-polarized electron exchange between the ferromagnetic CoFe2O4 and the adsorbed oxygen species (reactants) for the first electron transfer is ferromagnetic-exchange-like under the principle of spin angular momentum conservation, which leads to faster reaction kinetics for the first electron transfer step. In contrast, such a phenomenon was not observed on non-ferromagnetic catalysts. The findings imply that the conservation of the total spin on the active sites during OER is an important concept, which applies quantum spin-exchange interactions to optimize reaction kinetics. The kinetic improvement maintains after the removal of the external magnetic field. The demagnetization can bring the activity back to that before magnetization. This work provides new understandings of the effect of an external magnetic field on the OER activity of a ferromagnetic catalyst.It is found that ferromagnetic CoFe2O4 oxides were synthesized by a modified conventional solid-state chemistry method as described elsewhere45 with Fe(NO3)2 and Co(NO3)2 as precursors. 9 mmol mixture of Fe(NO3)3·9H2O (Alfa Aesar) and Co(NO3)2ˑ6H2O (Sigma–Aldrich) was dissolved in 15 mL of DI water, followed by stirring and vaporizing in oven at 80 °C. The resulting slurry was calcinated at 250 °C for 2 h in the air to decompose nitrous completely. After grinding, the black oxide powders underwent calcination in air at 400 °C for 8 h. Co3O4 oxides were synthesized by the same method.Spinel CoFe2), a counter electrode of platinum foil, and a Hg/HgO reference electrode (RE) (filled with 1 M KOH solution). The catalysts electrode was fabricated by the recipe drop-castes method, which was reported in elsewhere63. The catalysts were mixed with acetylene black (AB) at a mass ration of 5:1, then were dispersed in isopropanol/water (v/v = 1:4) solvent followed by the addition of Na+-exchanged Nafion as the binder. The mixtures were ultrasonicated for 30 min to reach homogeneous ink. The concentration of oxides in ink is 5 mg/ml, and AB is 1 mg/ml. Before drop-casting, the glassy carbon electrodes were polished to a mirror finish with α-Al2O3 (50 nm) and washed by IPA and water to clean up completely. Finally, the as-prepared ink (100 ul) was dropped onto glassy carbon electrodes to reach a loading mass of 500 μgox cm−2 and the electrodes were dried overnight at room temperature. Cyclic voltammograms (CVs), linear sweep voltammetry (LSV), and chronoamperometry (CA) were performed in O2-saturated 1 M KOH by using Bio-logic SP 150 potentiostat. All potentials were converted to RHE scale according to the following equation: RHE = Hg/HgO + 0.098 with iR correction. The tests of methanol oxidation reaction (MOR) and ethylene glycol oxidation reaction (EGOR) on CFO electrodes are similar to the OER test. The difference is that the MOR and EGOR were studied in 1 M KOH 100 ml electrolyte in the presence of 1 ml methanol and 1 ml ethylene glycol, respectively64.The OER tests were operated in a three-electrode cell with a working electrode (WE) of glassy carbon flake . DC magnetization measurements were performed on a Superconducting Quantum Design (SQUID) magnetometer (MPMS-XL). The SQUID measurements of the magnetization of samples as a function of the magnetic field were carried out at 300 K in fields between −5 T and +5 T. The high-resolution transmission electron microscopy (HRTEM) was carried JEOL JEM- 2100 plus microscope at 200KV. The STEM results presented here were obtained using the 200 kV JEOL ARM electron microscope equipped  with double aberration correctors, a dual-energy-loss spectrometer and a cold field emission source. The atomic-resolved STEM images were collected with a condense aperture of 28 mrad and a collection angle of 90–370 mrad for HAADF and 11–23 mrad for ABF images. The XPS measurements were performed using PHI-5400 equipment with Al Kα beam source (250 W) and a position-sensitive detector (PSD) was used to determine the surface composition of the materials. The Fourier transform infrared spectroscopy–Raman spectroscopy was carried with a confocal Raman microscope (Horiba HR Evolution), equipped with a diode laser emitting at 532 nm. The nominal laser power was filtered down to 1 mW to avoid sample overheating. Spectra were recorded with the accumulation time of 60 s.The X-ray diffraction (XRD) of oxides were carried on Bruker D8 diffractometer at a scanning rate of 2° min66 (VASP), employing the Projected Augmented Wave67 (PAW) method. The revised Perdew-Burke-Ernzerhof (RPBE) functional was used to describe the exchange and correlation effects.70 The GGA + U calculations are performed using the model proposed by Dudarev et al.71, with the Ueff (Ueff = Coulomb U – exchange J) values of 3.3 eV and 4 eV for Co and Fe, respectively. For all the geometry optimizations, the cutoff energy was set to be 500 eV. A 3 × 3 × 1 Monkhorst-Pack grids72 was used to carry out the surface calculations on the (111) surface of CoFe2O4. At least 20 Å vacuum layer was applied in z-direction of the slab models, preventing the vertical interactions between slabs.All the density functional theory (DFT) calculations were performed by Vienna Ab-initio Simulation Package73 was used to calculate the free energies of OER, based on which the free energy of an adsorbed species is defined asEads is the electronic adsorption energy, ∆EZPE is the zero point energy difference between adsorbed and gaseous species, and T∆Sads is the corresponding entropy difference between these two states. The electronic binding energy is referenced as ½ H2 for each H atom, and (H2O – H2) for each O atom, plus the energy of the clean slab. The corrections of zero point energy and entropy of the OER intermediates can be found in the Supplementary Table In alkaline conditions, OER could occur in the following four elementary steps:Supplementary InformationPeer Review File


The effect of comorbid hypertension and type 2 diabetes mellitus (T2DM) on coronary artery plaques examined by coronary computed tomography angiography (CCTA) is not fully understood. We aimed to comprehensively assess whether comorbid hypertension and T2DM influence coronary artery plaques using CCTA.A total of 1100 T2DM patients, namely, 277 normotensive [T2DM(HTN−)] and 823 hypertensive [T2DM(HTN +)] individuals, and 1048 normotensive patients without T2DM (control group) who had coronary plaques detected on CCTA were retrospectively enrolled. Plaque type, coronary stenosis, diseased vessels, the segment involvement score (SIS) and the segment stenosis score (SSS) based on CCTA data were evaluated and compared among the groups.Compared with patients in the control group, the patients in the T2DM(HTN−) and T2DM(HTN +) groups had more partially calcified plaques, noncalcified plaques, segments with obstructive stenosis, and diseased vessels, and a higher SIS and SSS . Compared with the control group, T2DM(HTN +) patients had increased odds of having any calcified and any noncalcified plaque ; both the T2DM(HTN-) and T2DM(HTN +) groups had increased odds of having any partially calcified plaque , obstructive coronary artery disease (CAD) , multivessel disease , an SIS > 3  and an SSS > 5 . Compared to T2DM(HTN−) patients, T2DM(HTN +) patients had an increased risk of any partially calcified plaque , multivessel disease , an SIS > 3  and an SSS > 5 .T2DM is related to the presence of partially calcified plaques, obstructive CAD, and more extensive coronary artery plaques. Comorbid hypertension and diabetes further increase the risk of partially calcified plaques, and more extensive coronary artery plaques. Type 2 diabetes mellitus (T2DM) and essential hypertension, two of the most common chronic diseases threatening global public health, are frequently comorbid . ApproxiCoronary artery disease (CAD) is the most common cardiovascular disease. Coronary computed tomography angiography (CCTA) has been widely accepted as a promising non-invasive tool for assessing coronary atherosclerosis. Clinical decision-making and planning for patients based on CCTA data show high agreement with those based on conventional coronary angiography data . MoreoveEvidence from previous studies suggests a severe coronary plaque burden in patients with hypertension or T2DM –10, wherThis study was approved by the Biomedical Research Ethics Committee of our hospital, and written informed consent was waived due to the retrospective nature of this study.2 adjacent to the coronary artery lumen or within the vessel lumen that could be distinguished from the surrounding pericardial tissue or the artery lumen itself [2] (n = 43). Consequently, 1100 T2DM patients with or without essential hypertension  were enrolled in our study. Another 1048 patients with positive coronary plaque findings based on CCTA but without T2DM or hypertension who were unmatched for age and sex were selected to serve as the control group; the exclusion criteria mentioned above for patients with T2DM also applied to the control subjects.Between January 2018 and March 2021, a total of 1420 T2DM patients with coronary plaque detected on CCTA in our hospital were retrospectively reviewed. Coronary plaque was defined as structures > 1 mmn itself . The dian itself . HyperteThe CCTA examinations were performed using Siemens CT scanners  or a Revolution CT scanner  with patients in the supine position. An intravenous bolus injection of 70–90 ml (based on body weight) of iodinated contrast agent  at a flow rate of 5 ml/s was followed by a 30 ml saline flush at the same flow rate. The scan range was from the tracheal bifurcation to 20 mm below the inferior cardiac apex. For the SOMATOM Definition systems, the parameters were as follows: tube voltage, 100–120 kV; tube current, 220 mAs; collimation, 64/128 × 0.5 mm; and rotation time, 0.33 s–0.4 s. For the Revolution CT, the parameters were as follows: the tube voltage and tube current were modulated automatically by kV Assist and Smart-mA on the basis of the scout image, collimation was 256 × 0.625 mm, and rotation time was 0.28 s. Either a retrospective electrocardiogram-gated or a prospective electrocardiographic gating protocol was used for CCTA image acquisition. Subsequently, the initial data set was reconstructed upon completion of the scan, and images were transferred to image-processing workstations  for image analysis.The presence of plaque and luminal stenosis was assessed for each evaluable coronary segment. Plaques were visually classified as calcified plaque (CT attenuation of plaque higher than contrast-enhanced coronary lumen), noncalcified plaque  and partially calcified plaque  Fig.  13]. Th. Th13]. Continuous variables are expressed as the mean ± standard deviation and categorical variables are presented as numbers (%) in this study. The comparison of continuous variables among groups was performed using one-way analysis of variance or the Kruskal–Wallis rank test, and comparison of categorical variables was performed using the chi-square test followed by Bonferroni’s post-hoc test. The comparisons for diabetes duration and diabetes treatment between the T2DM(HTN +) and T2DM(HTN−) groups were performed using the Mann–Whitney U test and chi-square test, respectively. Multivariate logistic regression adjusted for confounding factors was used to analyse the associations of plaque characteristics among the groups. The presence of each type of plaque, extent of luminal narrowing, involved branch, SIS and SSS were statistically analysed for each patient. For all analyses, a two-tailed P value of less than 0.05 was considered indicative statistical significance. All statistical analyses were performed using SPSS software .The main clinical characteristics of the participants in the study are summarized in Table A total of 8926 coronary plaques, 5036 diseased vessels and 8868 diseased segments were analysed. The plaque burden, plaque extent and coronary artery stenosis caused by plaques among the groups are shown in Table Regarding segment stenosis caused by plaques, patients in the control group had the fewest segments with obstructive stenosis among the three groups   group had the greatest number of diseased vessels and segments and the highest SSS, followed by the T2DM(HTN−) group   patients had a higher risk of more extensive and severe CAD than patients in control group after adjusting for confounding factors, and T2DM patients with hypertension had a higher risk than those without hypertension. A possible explanation could be the common pathogenesis and development process of atherosclerosis shared by diabetes and CAD, and comorbid diabetes and hypertension dramatically increase the risk of cardiovascular disease , 27. ThePatients with extensive CAD can benefit from surgical revascularization , 33. ForThere are some limitations of this study. First, the evaluation of coronary plaque was based on visual assessment of CCTA images. However, visual assessment of CCTA has been widely used and validated for evaluating the characteristics and progression of coronary plaques in CAD patients , 38. TheIn conclusion, T2DM is related to the presence of partially calcified plaques, obstructive CAD and more extensive coronary artery plaques. Comorbid hypertension and diabetes further increase the risk of partially calcified plaques and more extensive coronary artery plaques; however, they have little effect on the risk of obstructive CAD compared with T2DM without hypertension.


The canted spin structure of Mn guarantees a non-zero Berry curvature, but generates only a weak magnetization three orders of magnitude lower than that of general ferromagnets. The heavy Bi with a large spin–orbit coupling enables a large ANE and low thermal conductivity, whereas its highly dispersive px/y orbitals ensure low resistivity. The high anomalous transverse thermoelectric performance and extremely small magnetization make YbMnBi2 an excellent candidate for transverse thermoelectrics.A large anomalous Nernst effect (ANE) is crucial for thermoelectric energy conversion applications because the associated unique transverse geometry facilitates module fabrication. Topological ferromagnets with large Berry curvatures show large ANEs; however, they face drawbacks such as strong magnetic disturbances and low mobility due to high magnetization. Herein, we demonstrate that YbMnBi 2 has an ANE thermopower of 3 μV K−1, similar to ferromagnets, and a larger ANE conductivity.The anomalous Nernst effect (ANE) in topological materials with large Berry curvature shows great potential for transverse thermoelectrics, but antiferromagnets typically show small ANEs. The antiferromagnet YbMnBi In the past few decades, many good longitudinal thermoelectric materials have been demonstrated to be topological insulators5. Recently, with the emergence of topological semimetals, the anomalous Nernst effect (ANE) has attracted increasing attention for transverse thermoelectric applications10. Owing to the large Berry curvature near the Fermi energy, large-ANE thermopowers have been achieved in a few topological ferromagnets12, which show great potential for stable and precise temperature control, particularly in micro- or nanosized devices14. For example, Co3Sn2S2 (refs. 8), Co2MnGa (refs. 9) and Fe3Ga (ref. 2) showed ANE thermopowers of 3–8 μV K−1 and ANE conductivities of 0.5–5 A m−1 K−1, and recently UCo0.8Ru0.2Al (ref. 15) was reported to have a colossal ANE thermopower of 23 μV K−1 and a large ANE conductivity of 15 A m−1 K−1. So far, large ANEs have been reported in only a few topological ferromagnets, and topological noncollinear antiferromagnets have rarely been studied, except for Mn3X (X = Sn and Ge)12. The search for large ANEs in noncollinear topological antiferromagnets will yield advantages by broadening the material platform for transverse thermoelectrics, as well as revealing novel topological phenomena.Topological electronic structures lay the foundation for new functionalities and are crucial for various applications, including thermoelectric energy conversion16. From these viewpoints, ANE efficiency is coupled with various parameters, similar to the longitudinal Seebeck effect17, and additional magnetization makes the coupling more complicated. For ferromagnets in general, although strong ferromagnetism breaks time-reversal symmetry and offers a large Berry curvature, it also has some drawbacks. With local moment and itinerant electrons  at the Fermi energy (EF), these ferromagnets mostly have relatively low mobility and high resistivity. In addition, the high magnetization and strong inherent stray field of ferromagnets introduce a strong magnetic disturbance, which causes interference with other electronic devices in practical applications.To use the ANE for practical applications, low resistivity and thermal conductivity are also required. Moreover, at the device level, low magnetization and a small inherent stray field are important to eliminate magnetic disturbances and stabilize the remanent magnetization in the in-plane direction if using in a thin-film casep bands or p–d hybridization near EF. YbMnBi2, as a canted antiferromagnet, can simultaneously realize broken time-reversal symmetry and relatively low resistivity with light band conduction. The canted spin structure at Mn sites breaks time-reversal symmetry. Meanwhile, low resistivity can be achieved owing to the sharp dispersion of the px/y orbitals of Bi. Moreover, the large spin–orbit coupling (SOC) from Bi is critical for band topology, transverse transport response and low thermal conductivity. Furthermore, the YbMnBi2 canted antiferromagnet has much smaller magnetization and inherent stray fields than other ferromagnets. All of these features demonstrate that YbMnBi2 could provide a new material platform beyond ferromagnets for transverse thermoelectric applications.Herein, considering the challenges outlined above, we highlight the importance of searching for materials with broken time-reversal symmetry and 18. In contrast, the Nernst device . A few canted manganese pnictides—such as SrMnSb2 (ref. 20), YbMnBi2 (ref. 21) and Cax1−NaxMnBi2 (ref. 22)—are reported to be magnetic topological materials with a canted spin structure; they are therefore able to hold a non-zero Berry curvature24. Moreover, the bands contributed by pnictides are highly dispersive25, which can provide a low resistivity, especially compared with that of ferromagnets.We have reviewed the magnetic topological materials identified recently by high-throughput calculations2 was investigated. As shown in Fig. 2 crystallizes in a P4/nmm structure with two types of Bi: Bi 1 is bonded with Mn and Bi 2 forms an interlayer. The spin of Mn is antiferromagnetic along the c axis but canted in the ab plane. The Néel temperature was reported to be ~290 K (ref. 26), which is very close to that shown in Fig. −3 μB per formula unit (f.u.) in the ab plane, suggesting a very small canting angle (θ) of approximately 0.018°. Although the spin canting is very weak and may even be inaccessible in experiments requiring a strong signal27, it plays a crucial role in the anomalous thermal/electrical transport by inducing a non-zero Berry curvature.Given that Yb is relatively stable, Mn has a canted spin structure and Bi can induce large SOC, YbMnBi2 has unique topological properties. When the SOC is ignored, a nodal line protected by glide-plane symmetry exists in the Brillouin zone because of the band inversion of the px/y orbitals of Bi 2, as shown by the yellow line in Fig. EF, and reaches its maximum when EF is near the Weyl nodes. As schematically illustrated in Fig. EF would probe the strength of the Berry curvature, therefore leading to the varying strength of the anomalous Hall effect (AHE) conductivity (σAHE) and the ANE conductivity (αANE)30. In this case, it is essential to optimize EF to observe a large σAHE or αANE, which are usually related to the quality of the single crystal.Owing to the canted spin structure, YbMnBi21, the magnetic point group of YbMnBi2 becomes m′m2′, and only transverse transport signals in the ac/bc and ca/cb configurations can be observed owing to mirror symmetry31. Taking the cb configuration as an example, this implies that the transverse signal is measured along the c axis while a temperature gradient is applied along the b axis and a magnetic field along the a axis. Experimental results are highly consistent with theoretical predictions: both the ANE and AHE are observed in the bc and cb configurations, but not in the ab plane SANE) and AHE resistivity (ρAHE) 2. SANE first increases and then decreases with heating, showing a peak at ~160 K  and ~1.2 µV K−1 in Mn3Ge (refs. 32).The ANE thermopower , we first investigated σAHE, followed by αANE. Two characteristics of the band structure are essential to understand the AHE and ANE. First, the hole pocket near the Г point, which stems from the hybridization of the pz orbitals of Bi 1 and the d orbitals of Mn, should be far below EF if θ is zero  also generate a negative Berry curvature , which therefore allowed us to roughly assess σAHE at extremely small θ.To quantitatively understand the origin of the ANE and AHE in YbMnBiero Fig. . The holure Fig. . As show2 are strongly anisotropic and highly dispersive in the ab plane  = −ρcb(−Ha) 34 and the same relation would be expected to hold for the conductivity tensors. The fact that this is not observed in Fig. Sbc(Ha) ≠ −Scb(−Ha)  ≠ −αcb(−Ha) , Co2MnGa (ref. 9), Fe3Ga (ref. 2) and SmCo5  and one order of magnitude higher than those of the antiferromagnets Mn3X (X = Sn (refs. 12) and Ge (refs. 32)).As shown in Fig. Ha) Fig.  and αbc(Ha) Fig.  is allowαANE in addition to the Berry curvature, particularly considering the following three aspects. First, there is a mismatch between the experimental results and those from first-principles predictions. The calculated |αANE| is much lower than the experimental αbc, even when EF was optimized  = −Ωji(k). Third, a large violation of the ratio of |αbc/σbc| from an empirical value of kB/e (where kB is the Boltzmann constant) was observed 32, have small SOC without heavy elements, which is not the case here. Very recently, Papaj and Fu41 indicated that extrinsic contributions can be dramatic, and even potentially dominant over Berry curvature. To accurately describe αANE, vast improvements to current modelling techniques, beyond the simple single band models, are necessary. Such improvements include, but are not limited to, the modelling of band anisotropy, deviations from a linear band dispersion and interactions of point defects with electrons41. The strong band anisotropy in YbMnBi2 has rarely been observed in other materials with large ANEs. We highlight that the strong anisotropy in the Fermi surface of YbMnBi2 plays a critical role in achieving large αANE in the bc configuration and not in the cb configuration. The electron pockets are highly dispersive in the ab plane but have nearly no dispersion along the c axis, leading to a considerable difference in the extrinsic scattering effects on charge carriers between the bc and cb configurations. The extremely high σbb (which is ~35 times higher than σcc at 80 K), along with asymmetric skew scattering rates, results in large αANE in only the bc configuration. Future investigations are warranted to explore both the intrinsic  and extrinsic  contributions to the large αANE in more detail.In fact, extrinsic contributions are possible in real crystals owing to the unavoidable presence of scattering—particularly for systems with large SOC, which is the case for YbMnBi2 presents extremely small magnetization M, which can reduce the interaction of the magnetic field with surrounding electronic devices during practical applications. Figure αANE|/M, |SANE|/M and M of YbMnBi2 with those of other compounds with large SANE—namely, the ferromagnets Fe3Ga (ref. 2), Co2MnGa (refs.9), Co3Sn2S2 (ref. 7), UCo0.8Ru0.2Al (ref. 15), MnBi (ref. 37) and Gax1−MnxAs (ref. 42) and the chiral antiferromagnets Mn3Sn (refs. 12) and Mn3Ge (refs. 32). The noncollinear antiferromagnets, especially YbMnBi2, clearly surpass all of the ferromagnets in terms of |αANE|/M and |SANE|/M, demonstrating that canted antiferromagnets, even with extremely low magnetization, can display a large ANE that competes with the best ferromagnets. For practical applications, using permanent magnets  is reasonable for materials with no remanent magnetization, such as YbMnBi2. Further exploration of the zero-field ANEs of polycrystals and/or thin films would be of interest for future devices.In addition to the large ANE signals, YbMnBiρbb and low κcc  . As shown in Fig. 2 has high zTANE values over a wide temperature range, demonstrating its highly promising anomalous transverse thermoelectric performance. Although the zTANE values are still much lower than the traditional, longitudinal zT, we present this result as promising progress towards the use of the ANE in thermoelectric applications, which could ultimately offer improvements in microscale devices and the field of spin caloritronics.In addition to the large ANE signals (owing to the anisotropy), the resistivity and thermal conductivity can be decoupled to realize simultaneous gains in both—that is, low 2, a canted antiferromagnet, breaks time-reversal symmetry and yields a non-zero Berry curvature. Alongside the large SOC contributed by the heavy Bi atoms, a large ANE conductivity of 10 A m−1 K−1 was observed, which is two to three times larger than those of most of the ferromagnets and compares favourably with those of noncollinear antiferromagnets. This is of great interest, particularly considering its small magnetization. Furthermore, it shows strong anisotropy, making it possible to achieve low resistivity and low thermal conductivity simultaneously in transverse thermoelectric configurations. All of these unique features demonstrate the great potential of YbMnBi2 as a transverse thermoelectric material.In summary, YbMnBiRMnPn2 family, are worthy of further investigation for large ANEs. Future studies searching for compounds with canting temperatures higher than room temperature are crucial. Moreover, investigating the use of polycrystalline or thin-film materials to induce remanent magnetizations could be important for practical applications without external magnetic fields. Precise tuning of the Fermi level would also be an efficient way to enhance the ANE. Finally, with a deeper understanding of the intrinsic and extrinsic contributions to the ANE, both experimentally and theoretically, we expect to achieve boosted ANEs in more topological materials.These results suggest that canted antiferromagnets, including (but not limited to) the 44. To calculate the band structure, the Perdew–Burke–Ernzerhof exchange-correlation functional and projector-augmented-wave approach were used. The cut-off energy was set at 500 eV to expand the wavefunctions into a plane–wave basis. The Brillouin zone was sampled in the k-space within the Monkhorst–Pack scheme45, and a k mesh of 10 × 10 × 4 was adopted based on an equilibrium structure. The C-type antiferromagnetic order along the c axis at the Mn sites, a canted spin structure and SOC were considered. To calculate the anomalous Hall conductivity and anomalous Nernst conductivity, the ab initio density functional theory Bloch wavefunction was projected onto highly symmetric atomic-orbital-like Wannier functions46 with a diagonal position operator using VASP code44. To obtain precise Wannier functions, we included the outermost s and d orbitals for Yb, d orbital for Mn and p orbital for Bi to cover the full band overlap from the ab initio and Wannier functions. The atomic coordinates for the electronic structure calculations are shown in Supplementary Table Calculations were conducted using density functional theory implemented in the Vienna ab initio simulation package (VASP) code2 single crystals were grown using a self-flux method with an elemental ratio of Yb:Mn:Bi of 1:1:4. Yb (99.99%), Mn (99.98%) and Bi (99.999%) were cut into small pieces and mixed before being placed in an alumina crucible. They were then sealed in a quartz tube under a partial argon pressure. The sealed tube was heated to 1,050 °C over 2.5 days and maintained at that tempearture for 24 h. Next, it was slowly cooled to 400 °C at a rate of 2 °C h−1, and single crystals were obtained by removing the flux through centrifugation.YbMnBiThe single crystallinity and orientation of the as-grown single crystals were determined using Laue X-ray diffraction .Resistivities and Hall resistivities were measured using a physical property measurement system  in an electrical transport option via a standard four-probe method. The Nernst thermopower, Seebeck coefficient and thermal conductivity were measured in the PPMS9 under a high vacuum by using a standard four-contact steady-state methodAny methods, additional references, Nature Research reporting summaries, source data, extended data, supplementary information, acknowledgements, peer review information; details of author contributions and competing interests; and statements of data and code availability are available at 10.1038/s41563-021-01149-2.Supplementary InformationSupplementary Figs. 1–13, Tables 1 and 2, Discussion and refs. 1–16.