Resolving Ultraviolet-Visible Spectra for Complex Dissolved Mixtures of Multitudinous Organic Matters in Aerosols.

Light-absorbing organic aerosols, referred to as brown carbon (BrC), play a vital role in the global climate and air quality. Due to the complexity of BrC chromophores, the identified absorbing substances in the ambient atmosphere are very limited. However, without comprehensive knowledge of the complex absorbing compounds in BrC, our understanding of its sources, formation, and evolution mechanisms remains superficial, leading to great uncertainty in climatic and atmospheric models. To address this gap, we developed a constrained non-negative matrix factorization (NMF) model to resolve the individual ultraviolet-visible spectrum for each substance in dissolved organic aerosols, with the power of ultrahigh-performance liquid chromatography-diode array detector-ultrahigh-resolution mass spectrometry (UHPLC-DAD-UHRMS). The resolved spectra were validated by selected standard substances and validation samples. Approximately 40,000 light-absorbing substances were recognized at the MS1 level. It turns out that BrC is composed of a vast number of substances rather than a few prominent chromophores in the urban atmosphere. Previous understanding of the absorbing feature of BrC based on a few identified compounds could be biased. Weak-absorbing substances missed previously play an important role in BrC absorption when they are integrated due to their overwhelming number. This model brings the property exploration of complex dissolved organic mixtures to a molecular level, laying a foundation for identifying potentially significant compositions and obtaining a comprehensive chemical picture.

Coordination-Controlled Catalytic Activity of Cobalt Oxides for Ozone Decomposition.

Nowadays, it is still elusive and challenging to discover the active sites of cobalt (Co) cations in different coordination structures, though Co-based oxides show their great potency in catalytic ozone elimination for air cleaning. Herein, different Co-based oxides are controllably synthesized including hexagonal wurtzite CoO-W with Co2+ in tetrahedral coordination (CoTd2+) and CoAl spinel with dominant CoTd2+, cubic rock salt CoO-R with Co2+ in octahedral coordination (CoOh2+), MgCo spinel with dominant Co3+ in octahedral coordination (CoOh3+), and Co3O4 with mixed CoTd2+ and CoOh3+. The valences are proved by X-ray photoelectron spectroscopy, and the coordinations are verified by X-ray absorption fine structure analysis. The ozone decomposition performances are CoOh3+ ∼ CoOh2+ ≫ CoTd2+, and CoOh3+ and CoOh2+ show a lower apparent activation energy of ∼42-44 kJ/mol than CoTd2+ (∼55 kJ/mol). In specific, MgCo shows the highest decomposition efficiency of 95% toward 100 ppm ozone at a high space velocity of 1,200,000 mL/gh, which still retains at 80% after a long-term running of 36 h at room temperature. The high activity is explained by the d-orbital splitting in the octahedral coordination, favoring the electron transfer in ozone decomposition reactions, which is also verified by the simulation. These results show the promising prospect of the coordination tuning of Co-based oxides for highly active ozone decomposition catalysts.

Heterojunctioned CuO/Cu2O catalyst for highly efficient ozone removal.

In recent years, near surface ozone pollution, has attracted more and more attention, which necessitates the development of high efficient and low cost catalysts. In this work, CuO/Cu2O heterojunctioned catalyst is fabricated by heating Cu2O at high temperature, and is adopted as ozone decomposition catalyst. The results show that after Cu2O is heated at 180°C conversion of ozone increases from 75.2% to 89.3% at mass space velocity 1,920,000 cm3/(g·hr) in dry air with 1000 ppmV ozone, which indicates that this heterojunction catalyst is one of the most efficient catalysts reported at present. Catalysts are characterized by electron paramagnetic resonance spectroscopy and ultraviolet photoelectron spectroscopy, which confirmed that the heterojunction promotes the electron transfer in the catalytic process and creates more defects and oxygen vacancies in the CuO/Cu2O interfaces. This procedure of manufacturing heterostructures would also be applicable to other metal oxide catalysts, and it is expected to be more widely applied to the synthesis of high-efficiency heterostructured catalysts in the future.

Highly efficient ozone elimination by metal doped ultra-fine Cu2O nanoparticles.

Nowadays, ozone contamination becomes dominant in air and thus challenges the research and development of cost-effective catalyst. In this study, metal doped Cu2O catalysts are synthesized via reduction of Cu2+ by ascorbic acid in base solutions containing doping metal ions. The results show that compared with pure Cu2O, the Mg2+ and Fe2+ dopants enhance the O3 removal efficiency while Ni2+ depresses the activity. In specific, Mg-Cu2O shows high O3 removal efficiency of 88.4% in harsh environment of 600,000 mL/(g·hr) space velocity and 1500 ppmV O3, which is one of the highest in the literature. Photoluminescence and electron paramagnetic spectroscopy characterization shows higher concentration of crystal defects induced by the Mg2+ dopants, favoring the O3 degradation. The in-situ diffuse reflectance Fourier transform infrared spectroscopy shows the intermediate species in the O3 degradation process change from O22- dominant of pure Cu2O to O2- dominant of Mg-Cu2O, which would contribute to the high activity. All these results show the promising prospect of the Mg-Cu2O for highly efficiency O3 removal.

Non-Interacting Ni and Fe Dual-Atom Pair Sites in N-Doped Carbon Catalysts for Efficient Concentrating Solar-Driven Photothermal CO2 Reduction.

Solar-to-chemical energy conversion under weak solar irradiation is generally difficult to meet the heat demand of CO2 reduction. Herein, a new concentrated solar-driven photothermal system coupling a dual-metal single-atom catalyst (DSAC) with adjacent Ni-N4 and Fe-N4 pair sites is designed for boosting gas-solid CO2 reduction with H2 O under simulated solar irradiation, even under ambient sunlight. As expected, the (Ni, Fe)-N-C DSAC exhibits a superior photothermal catalytic performance for CO2 reduction to CO (86.16 µmol g-1 h-1 ), CH4 (135.35 µmol g-1 h-1 ) and CH3 OH (59.81 µmol g-1 h-1 ), which are equivalent to 1.70-fold, 1.27-fold and 1.23-fold higher than those of the Fe-N-C catalyst, respectively. Based on theoretical simulations, the Fermi level and d-band center of Fe atom is efficiently regulated in non-interacting Ni and Fe dual-atom pair sites with electronic interaction through electron orbital hybridization on (Ni, Fe)-N-C DSAC. Crucially, the distance between adjacent Ni and Fe atoms of the Ni-N-N-Fe configuration means that the additional Ni atom as a new active site contributes to the main *COOH and *HCO3 dissociation to optimize the corresponding energy barriers in the reaction process, leading to specific dual reaction pathways (COOH and HCO3 pathways) for solar-driven photothermal CO2 reduction to initial CO production.

Magnet-assisted electrochemical immunosensor based on surface-clean Pd-Au nanosheets for sensitive detection of SARS-CoV-2 spike protein.

Tracking and monitoring of low concentrations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can effectively control asymptomatic transmission of current coronavirus disease 2019 (COVID-19) in the early stages of infection. Here, we highlight an electrochemical immunosensor for sensitive detection of SARS-CoV-2 antigen marker spike protein. The surface-clean Pd-Au nanosheets as a substrate for efficient sensing and signal output have been synthesized. The morphology, chemical states and excellent stable electrochemical properties of this surface-clean heterostructures have been studied. Functionalized superparamagnetic nanoparticles (MNPs) were introduced as sample separators and signal amplifiers. This biosensor was tested in phosphate buffered saline (PBS) and nasopharyngeal samples. The results showed that the sensor has a wide linear dynamic range (0.01 ng mL-1 to 1000 ng mL-1) with a low detection limit (0.0072 ng mL-1), which achieved stable and sensitive detection of the spike protein. Therefore, this immunosensing method provides a promising electrochemical measurement tool, which can furnish ideas for early screening and the reasonable optimization of detection methods of SARS-CoV-2.

Roles of Oxygen Vacancies of CeO2 and Mn-Doped CeO2 with the Same Morphology in Benzene Catalytic Oxidation.

Mn-doped CeO2 and CeO2 with the same morphology (nanofiber and nanocube) have been synthesized through hydrothermal method. When applied to benzene oxidation, the catalytic performance of Mn-doped CeO2 is better than that of CeO2, due to the difference of the concentration of O vacancy. Compared to CeO2 with the same morphology, more oxygen vacancies were generated on the surface of Mn-doped CeO2, due to the replacement of Ce ion with Mn ion. The lattice replacement has been analyzed through XRD, Raman, electron energy loss spectroscopy and electron paramagnetic resonance technology. The formation energies of oxygen vacancy on the different exposed crystal planes such as (110) and (100) for Mn-doped CeO2 were calculated by the density functional theory (DFT). The results show that the oxygen vacancy is easier to be formed on the (110) plane. Other factors influencing catalytic behavior have also been investigated, indicating that the surface oxygen vacancy plays a crucial role in catalytic reaction.

Effects of Hollow CeO2 Nanospheres on Flame Retardance and Smoke Suppression of Room-Temperature-Vulcanized Silicone Rubber.

The effects of hollow CeO2 nanospheres on the flame-retardance and smoke-suppression properties of room-temperature-vulcanized (RTV) silicone rubber were studied. It was observed that the flame retardance of RTV silicone rubber composites was improved by hollow CeO2 nanospheres. Surprisingly, the nanospheres also enhanced the smoke-suppression characteristics of the composites. The limited oxygen index of RTV/Mg(OH)2 was raised from 23.7 to 25.9 by the addition of hollow CeO2 nanospheres, while the smoke density was reduced markedly, from 35.1 to 17.6. The thermal stability and char yield of the RTV silicone rubber composites were characterized by thermogravimetric techniques. Furthermore, the degradation product of the composites was analyzed by pyrolysis-gas chromatography-mass spectroscopy. A mechanism to explain the observed results is proposed.

Macroporous Ni foam-supported Co3O4 nanobrush and nanomace hybrid arrays for high-efficiency CO oxidation.

Herein, we reported the synthesis of well-defined Co3O4 nanoarrays (NAs) supported on a monolithic three-dimensional macroporous nickel (Ni) foam substrate for use in high-efficiency CO oxidation. The monolithic Co3O4 NAs catalysts were obtained through a generic hydrothermal synthesis route with subsequent calcination. By controlling the reaction time, solvent polarity and deposition agent, these Co3O4 NAs catalysts exhibited various novel morphologies (single or hybrid arrays), whose physicochemical properties were further characterized by using several analytical techniques. Based on the catalytic and characterization analyses, it was found that the Co3O4 NAs-6 catalyst with nanobrush and nanomace arrays displayed enhanced catalytic activity for CO oxidation, achieving an efficient 100% CO oxidation conversion at a gas hourly space velocity (GHSV) 10,000hr-1 and 150°C with long-term stability. Compared with the other Co3O4 NAs catalysts, it had the highest abundance of surface-adsorbed oxygen species, excellent low-temperature reducibility and was rich in surface-active sites (Co3+/Co2+=1.26).

General Synthesis of Transition-Metal Oxide Hollow Nanospheres/Nitrogen-Doped Graphene Hybrids by Metal-Ammine Complex Chemistry for High-Performance Lithium-Ion Batteries.

We present a general and facile synthesis strategy, on the basis of metal-ammine complex chemistry, for synthesizing hollow transition-metal oxides (Co3 O4 , NiO, CuO-Cu2 O, and ZnO)/nitrogen-doped graphene hybrids, potentially applied in high-performance lithium-ion batteries. The oxygen-containing functional groups of graphene oxide play a prerequisite role in the formation of hollow transition-metal oxides on graphene nanosheets, and a significant hollowing process occurs only when forming metal (Co2+ , Ni2+ , Cu2+ , or Zn2+ )-ammine complex ions. Moreover, the hollowing process is well correlated with the complexing capacity between metal ions and NH3 molecules. The significant hollowing process occurs for strong metal-ammine complex ions including Co2+ , Ni2+ , Cu2+ , and Zn2+ ions, and no hollow structures formed for weak and/or noncomplex Mn2+ and Fe3+ ions. Simultaneously, this novel strategy can also achieve the direct doping of nitrogen atoms into the graphene framework. The electrochemical performance of two typical hollow Co3 O4 or NiO/nitrogen-doped graphene hybrids was evaluated by their use as anodic materials. It was demonstrated that these unique nanostructured hybrids, in contrast with the bare counterparts, solid transition-metal oxides/nitrogen-doped graphene hybrids, perform with significantly improved specific capacity, superior rate capability, and excellent capacity retention.

Coupling p+n Field-Effect Transistor Circuits for Low Concentration Methane Gas Detection.

Nowadays, the detection of low concentration combustible methane gas has attracted great concern. In this paper, a coupling p+n field effect transistor (FET) amplification circuit is designed to detect methane gas. By optimizing the load resistance (RL), the response to methane of the commercial MP-4 sensor can be magnified ~15 times using this coupling circuit. At the same time, it decreases the limit of detection (LOD) from several hundred ppm to ~10 ppm methane, with the apparent response of 7.0 ± 0.2 and voltage signal of 1.1 ± 0.1 V. This is promising for the detection of trace concentrations of methane gas to avoid an accidental explosion because its lower explosion limit (LEL) is ~5%. The mechanism of this coupling circuit is that the n-type FET firstly generates an output voltage (VOUT) amplification process caused by the gate voltage-induced resistance change of the FET. Then, the p-type FET continues to amplify the signal based on the previous VOUT amplification process.

Transilient Response to Acetone Gas Using the Interlocking p+n Field-Effect Transistor Circuit.

Low concentration acetone gas detection is significantly important for diabetes diagnosis as 1.8⁻10 ppm of acetone exists in exhaled breath from diabetes patients. A new interlocking p+n field-effect transistor (FET) circuit has been proposed for Mn-doped ZnO nanoparticles (MZO) to detect the acetone gas at low concentration, especially close to 1.8 ppm. It is noteworthy that MZO in this interlocking amplification circuit shows a low voltage signal of <0.3 V to the acetone <2 ppm while it displays a transilient response with voltage signal >4.0 V to >2 ppm acetone. In other words, the response to acetone from 1 ppm to 2 ppm increases by ~1233%, which is competent to separate diabetic patients from healthy people. Moreover, the response to 2 ppm acetone is hardly influenced by high relative humidity of 85%. In the meanwhile, MZO in this interlocking circuit possesses a high acetone selectivity compared to formaldehyde, acetaldehyde, toluene and ethanol, suggesting a promising technology for the widespread qualitative screening of diabetes. Importantly, this interlocking circuit is also applicable to other types of metal oxide semiconductor gas sensors. The resistance jump of p- and n-FETs induced by the change of their gate voltages is deemed to make this interlocking circuit produce the transilient response.

Removal of hydrophobic volatile organic compounds with sodium hypochlorite and surfactant in a co-current rotating packed bed.

A co-current flow rotating packed bed was applied to remove volatile organic compounds (VOCs) by sodium hypochlorite (NaClO) and surfactant (sodium dodecyl benzene sulfonate, SDBS) from air stream. Xylene was used as a model VOC herein. The effect of pH, concentration of NaClO and SDBS solution, liquid flow rate, gas flow rate and rotational speed on xylene removal efficiency and overall mass transfer coefficient (KGa) were discussed. Then, a correlation for KGa of the co-current rotating packed bed was proposed by fitting the experimental data of KGa and independent variables of liquid/gas ratio, rotational speed, pH, NaClO concentration and treatment time, which was in good agreement with the experimental data (the deviation≤±30%).

Preparation and characterization of a novel hybrid chelating material for effective adsorption of Cu(II) and Pb(II).

The discharge of heavy metal ions such as Cu2+ and Pb2+ poses a severe threat to public health and the environment owing to their extreme toxicity and bioaccumulation through food chains. Herein, we report a novel organic-inorganic hybrid adsorbent, Al(OH)3-poly(acrylamide-dimethyldiallylammonium chloride)-graft-dithiocarbamate (APD), for rapid and effective removal of Cu2+ and Pb2+. In this adsorbent, the "star-like" structure of Al(OH)3-poly(acrylamide-dimethyldiallylammonium chloride) served as the support of dithiocarbamate (DTC) functional groups for easy access of heavy metal ions and assisted development of large and compact floccules. The synthesized adsorbent was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). APD was demonstrated to have rapid adsorption kinetics with an initial rate of 267.379 and 2569.373mg/(g·min) as well as superior adsorption capacities of 317.777 and 586.699mg/g for Cu2+ and Pb2+ respectively. The adsorption process was spontaneous and endothermic, involving intraparticle diffusion and chemical interaction between heavy metal ions and the functional groups of APD. To assess its versatility and wide applicability, APD was also used in turbid heavy metal wastewater, and performed well in removing suspended particles and heavy metal ions simultaneously through flocculation and chelation. The rapid, convenient and effective adsorption of Cu2+ and Pb2+ gives APD great potential for heavy metal decontamination in industrial applications.

Ag-Modified In2O3 Nanoparticles for Highly Sensitive and Selective Ethanol Alarming.

Pure In2O3 nanoparticles are prepared by a facile precipitation method and are further modified by Ag. The synthesized samples are characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Raman and UV-Vis spectra. The results show the successful heterojunction formation between Ag and In2O3. Gas sensing property measurements show that the 5 mol % Ag-modified In2O3 sensor has the response of 67 to 50 ppm ethanol, and fast response and recovery time of 22.3 and 11.7 s. The response is over one magnitude higher than that of pure In2O3, which can be attributed to the enhanced catalytic activity of Ag-modified In2O3 as compared with the pure one. The mechanism of the gas sensor can be explained by the spillover effect of Ag, which enhances the oxygen adsorption onto the surface of In2O3 and thus give rise to the higher activity and larger surface barrier height.

Characterization of a hybrid polyacrylamide and its flocculation properties in cyanide tailing suspensions.

An inorganic-organic hybrid flocculant Al(OH)3-polyacrylamide (Al-PAM) with narrow molecular weight distribution was synthesized using inverse microemulsion polymerization. The hybrid polymer Al-PAM was characterized by Infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy and scanning electron microscopy, and it was found that it had a 'star-like' structure in which Al(OH)3 colloidal particles acted as cores linking PAM chains. The properties of Al-PAM were investigated in flocculating 10 wt% cyanide tailing suspensions. It was found that as the amount of Al-PAMM1 with high molecular weight and aluminum content increased, the initial settling rate of particles accelerated, achieving the maximum 6.6 m/h, 17.3 times the rate of the control without flocculants. The turbidity of the supernatant decreased to 35 ± 2 NTU accordingly, compared to 353 ± 2 NTU of that in the control, which meant that 90.0% of turbidity was removed from the cyanide tailing suspensions. The flocculation mechanism was further explored by floccule size and ζ potential measurements. The superior performance of cationic Al-PAM in flocculating negatively charged particles compared to commercial non-ionic GG indicated that electrostatic repulsion between tailing particles was a crucial factor in deciding the flocculation performance of the polymer. The study demonstrated that both charge neutralization and bridge adsorption were conductive to the particle flocculation.

Determination of time- and size-dependent fine particle emission with varied oil heating in an experimental kitchen.

Particulate matter (PM) from cooking has caused seriously indoor air pollutant and aroused risk to human health. It is urged to get deep knowledge of their spatial-temporal distribution of source emission characteristics, especially ultrafine particles (UFP<100nm) and accumulation mode particles (AMP 100-665nm). Four commercial cooking oils are auto dipped water to simulate cooking fume under heating to 265°C to investigate PM emission and decay features between 0.03 and 10µm size dimension by electrical low pressure impactor (ELPI) without ventilation. Rapeseed and sunflower produced high PM2.5 around 6.1mg/m3, in comparison with those of soybean and corn (5.87 and 4.65mg/m3, respectively) at peak emission time between 340 and 460sec since heating oil, but with the same level of particle numbers 6-9×105/cm3. Mean values of PM1.0/PM2.5 and PM2.5/PM10 at peak emission time are around 0.51-0.66 and 0.23-0.29. After 15min naturally deposition, decay rates of PM1.0, PM2.5 and PM10 are 13.3%-29.8%, 20.1%-33.9% and 41.2%-54.7%, which manifest that PM1.0 is quite hard to decay than larger particles, PM2.5 and PM10. The majority of the particle emission locates at 43nm with the largest decay rate at 75%, and shifts to a larger size between 137 and 655nm after 15min decay. The decay rates of the particles are sensitive to the oil type.

Novel ALD-assisted growth of ZnO nanorods on graphene and its Cu2ZnSn(S(x)Se(1-x))4 solar cell application.

The hydrothermal growth of ZnO nanorods on graphene draws a specific interest for the advantages of low-temperature processability over a large area and low cost, but challenges still remain in directly growing uniform ZnO seed layers on pristine graphene without impairing its beneficial properties. In this work, the direct growth of ZnO seed layers on graphene via H2O-based atomic layer deposition (ALD) has been investigated. It is found that uniform ZnO thin films can be deposited on graphene via ALD using a combination of single-layer graphene/Cu stacks as substrates and a facile pre-H2O treatment process. After growing ZnO nanorods on graphene, its photovoltaic application in a Cu2ZnSn(SxSe1-x)4 (CZTSSe) solar cell is demonstrated. The performance of graphene-based cells approaches that of ITO-based cells with similar architectures, highlighting that graphene is a potential replacement for ITO in optoelectronic devices. The method reported herein for fabricating ZnO nanorods on graphene using ALD-ZnO as seed layers preserves its properties, and is thus applicable to a wide variety of graphene-based nanoelectronic devices.

The role of MoS2 as an interfacial layer in graphene/silicon solar cells.

The role of MoS2 as an effective interfacial layer in graphene/silicon solar cells is systematically investigated by varying MoS2 film annealing temperature and thickness. It is found that the power conversion efficiency (PCE) is increased by ∼100% from ∼2.3% to ∼4.4% with 80 °C annealed MoS2 film whereas it drops significantly to ∼0.6% with 200 °C annealed MoS2 film. The results are well explained based on the device energy band diagram. That is, the incorporation of MoS2(80) films leads to the formation of type II structure, facilitating hole transport; while valence band mismatch is formed with MoS2(200) films due to the increase in the work function of MoS2. Besides, the PCE increases gradually with decreasing MoS2 film thickness, and "saturates" at about 2 nm. The PCE can be further enhanced to ∼6.6% with the aid of silicon surface passivation. Our work demonstrates that MoS2 is an excellent interfacial layer to improve the PCE with low-temperature annealing (80 °C in air), which may be helpful in developing efficient and low-cost G/Si solar cells.

Leaves and fruits of Bauhinia (Leguminosae, Caesalpinioideae, Cercideae) from the Oligocene Ningming Formation of Guangxi, South China and their biogeographic implications.

BACKGROUND: The pantropical genus Bauhinia, along with the northern temperate Cercis and several tropical genera, bear bilobate, bifoliolate, or sometimes unifoliolate leaves, which constitute the tribe Cercideae as sister to the rest of the family Leguminosae based on molecular phylogenetics. Hence, the fossil record of Cercideae is pivotal to understand the early evolution and biogeographic history of legumes. RESULTS: Three fossil species of Bauhinia were described from the Oligocene Ningming Formation of Guangxi, South China. Bauhinia ningmingensis sp. nov. is characterized by its bifoliolate, pulvinate leaves bearing basal acrodromous primary veins and brochidodromous secondary veins. B. cheniae sp. nov. bears moderately or deeply bilobate, pulvinate leaves, with basal actinodromous primary veins and eucamptodromous secondary veins. B. larsenii D.X. Zhang et Y.F. Chen emend. possesses shallowly or moderately bilobate, pulvinate leaves bearing basal actinodromous primary veins and brochidodromous secondary veins, as well as elliptic, stipitate, non-winged, and oligo-seeded fruits. Meanwhile, previously reported Bauhinia fossils were reviewed, and those pre-Oligocene foliage across the world are either questionable or have been rejected due to lacking of reliable evidence for their pulvini or/and basal actinodromous or acrodromous venations. Besides Oligocene leaves and fruits presented here, foliage and/or wood of Bauhinia have been documented from the Miocene-Pliocene of Thailand, India, Nepal, Uganda, and Ecuador. CONCLUSIONS: Bauhinia has exhibited a certain diversity with bifoliolate- and bilobate-leafed species in a low-latitude locality-Ningming since at least the Oligocene, implying that the tropical zone of South China may represent one of the centres for early diversification of the genus. The reliable macrofossils of Bauhinia and Cercis have made their debut in the Eocene-Oligocene floras from mid-low latitudes and appeared to lack in the coeval floras at high latitudes, implying a possible Tethys Seaway origin and spread of legumes. However, detailed scenarios for the historical biogeography of Bauhinia and its relatives still need more robust dataset from palaeobotany and molecular phylogeny in future research.