Construction of 2D-2D TiO_2 nanosheet/layered WS_2 heterojunctions with enhanced visible-light-responsive photocatalytic activity

Constructing nanocomposites that combine the advantages of composite materials,nanomaterials,and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO2.In this study,2D‐2D TiO2 nanosheet/layered WS2(TNS/WS2)heterojunctions were prepared via a hydrothermal method.The structure and morphology of the photocatalysts were systematically characterized.Layered WS2(~4 layers)was wrapped on the surface of TiO2 nanosheets with a plate‐to‐plate stacked structure and connected with each other by W=O bonds.The as‐prepared TNS/WS2 heterojunctions showed higher photocatalytic activity for the degradation of RhB under visible‐light irradiation,than pristine TiO2 nanosheets and layered WS2.The improvement of photocatalytic activity was primarily attributed to enhanced charge separation efficiency,which originated from the perfect 2D‐2D nanointerfaces and intimate interfacial contacts between TiO2 nanosheets and layered WS2.Based on experimental results,a double‐transfer photocatalytic mechanism for the TNS/WS2 heterojunctions was proposed and discussed.This work provides new insights for synthesizing highly efficient and environmentally stable photocatalysts by engineering the surface heterojunctions.

深时重大生物和气候事件与全球变化:进展与挑战

地球自5.4亿年前现代生态系统形成至今,发生了多次与碳循环扰动有关的重大气候事件.这些事件的触发机制、发展过程、环境变化及其伴随的生物响应型式为科学评估当今全球变化背景下生物多样性现状提供重要借鉴.然而,古-今生态系统变化时间尺度大不相同,高分辨率关键环境因子(温度、CO_(2)、降雨量、海洋氧化还原条件等)在深时记录中亦难以获取,深时海陆生物多样性模式尚缺乏高分辨率记录.因此,当今全球变化与深时记录对比存在巨大鸿沟.地球5.4亿年以来大部分时间处于两极无冰的温室状态,期间伴随多次极冷和极热气候事件,但地球深时重大生物演化和气候事件的关系复杂.生物多样性在变冷的奥陶纪早期、晚古生代大冰期、晚新生代大冰期以及中-晚三叠世和白垩纪热室期均呈现稳定增加,而在奥陶纪末冰期快速降温期间和二叠纪末、三叠纪末、白垩纪末火山排气作用导致的快速升温过程中急剧下降.地质时期生物多样性对气候变化的不同响应型式表明,生物多样性变化的根本驱动因素可能不是简单的温度、大气CO_(2)浓度等环境因子的背景值高或低,而是环境因子的变化速率(环境变率).变率较小,环境相对稳定,生物有足够的时间适应环境变化,生物多样性不会丧失,甚至繁盛.反之,若环境因子变率过大,超出了生态系统的承受力,生物来不及适应,生物多样性就会显著降低,甚至引发大灭绝.已有模拟和计算表明,当今地球碳排放的速度有可能超过了地质历史时期任何一次生物大灭绝事件.因此,避免环境突变事件和生物大灭绝的再次发生成为政界、科学界和普通民众关注的焦点.打通地球多圈层界限,开展古-今地质记录、冷-热极端气候、海-陆生态系统和长-短时间尺度的综合对比研究,并通过建立适用于深时的地球系统模型,模拟重大生物和环境事件的背景与发生过程,是地球系统科学未来发展的重要方向.

Devonian integrative stratigraphy,biotas,and paleogeographical evolution of the Qinghai-Tibetan Plateau and its surrounding areas

The Devonian System in the Qinghai-Tibetan Plateau and its surrounding areas is widely distributed,diverse in lithotypes and rich in fossils.It records the crucial processes of continuous subduction and reduction of the Paleo-Asian Ocean in the northern hemisphere and the transformation of the Proto-Tethys Ocean into the Paleo-Tethys Ocean in the southern hemisphere.Thus,it is of great significance for explaining the global paleogeographic evolution,tectonic activities and biodiversity changes during this critical period.The blocks on both sides of the southern Tienshan suture zone and the Longmu Co-ShuanghuChangning-Menglian suture zone belong to different sedimentary systems and paleobiogeographic realms and regions,showing important tectonic paleogeographic partitioning significance.The two suture zones represent the main branches of the PaleoAsian Ocean and the Paleo-Tethys Ocean,respectively,and on this basis the Devonian System can be subdivided into three types:the Tienshan type,the Tethys type and the Gondwana type.Based on recent research progress on the Devonian stratigraphy and paleontology in combining provenance analysis and biotic characteristics in the Qinghai-Tibetan Plateau and surrounding areas,this paper aims to establish the latest integrative stratigraphic framework and conduct paleogeographic reconstruction,providing foundation for exploring the geological evolution and dynamic mechanisms of various terranes and blocks in the northern margin of Gondwana.The results indicate that the North Qiangtang,South Qiangtang,Simao,Baoshan and Tengchong terranes,as well as the Himalaya Tethys Zone and the South China Block have affinities with the Indian Block,while the Lhasa Terrane has affinities with the Australian Block,and may be located between the South China and Australian blocks.In the Emsian(Early Devonian),the South China Block separated from the northern margin of Gondwana,a process that was accompanied by the opening of the Jinshajiang-Ailaoshan Ocean.In the Middle Devonian,the mid-oceanic ridge of the Paleo-Tethys Ocean expanded rapidly,corresponding with a global sea-level rise,the widespread development of carbonate platforms and nadir values of Devonian seawater strontium isotopes.By the Late Devonian,the Paleo-Tethys Ocean had reached a considerable size,leading to abundant occurrences of Upper Devonian radiolarian cherts in the Paleo-Tethys suture zones.

Electrical anisotropy in two-dimensional reduced graphene oxide/polypyrrole-based ordered conjugated system ensure multi-stimulus response signal adapter

Electronic technology,based on signal conversion induced by voltage stimulation,forms the core foundation of the state-of-the-art intelligent devices,tools,and equipment.Such conversions are inherently binary and limited because they rely solely on voltage,which presents challenges for many emerging frontier applications.Here,a two-dimensional ordered conjugated system of reduced graphene oxide/polypyrrole(rGO/PPy)has been developed.Multi-stimulus response signal adapters have been constructed,utilizing the electrical anisotropy inherent in the rGO/PPy system.This electrical anisotropy,derived from the quasi-two-dimensional geometry of rGO/PPy,enables the device to produce distinct electrical signals in response to various stimuli.With effective responses to light and pressure,the two most common input stimuli other than voltage,it can output quaternary/denary signals and visual optical signals,as well as enables information encryption using passive devices.Furthermore,the signal adapter demonstrates high cyclic stability under repeated pressure and/or light loading.The successful development of this low-cost,scalable signal adapter paves the way for the next-generation of intelligent systems,promising advancements in human-computer interaction,electronic skin,biological implant equipment,and related fields.

Mercury oxidation and adsorption characteristics of potassium permanganate modified lignite semi-coke

The adsorption characteristics of virgin and potassium permanganate modified lignite semi-coke （SC） for gaseous Hg were investigated in an attempt to produce more effective and lower price adsorbents for the control of elemental mercury emission. Brunauer-Emmett- Teller （BET） measurements, X-ray powder diffraction （XRD） and X-ray photoelectron spectroscopy （XPS） were used to analyze the surface physical and chemical properties of SC, Mn-SC and Mn-H-SC before and after mercury adsorption. The results indicated that potassium permanganate modification had significant influence on the properties of semi-coke, such as the specific surface area, pore structure and surface chemical functional groups. The mercury adsorption efficiency of modified semi-coke was lower than that of SC at low temperature, but much higher at high temperature. Amorphous Mn7＋, Mn6＋ and Mn4＋ on the surface of Mn-SC and Mn-H-SC were the active sites for oxidation and adsorption of gaseous Hg~, which oxidized the elemental mercury into Hg2＋ and captured it. Thermal treatment reduced the average oxidation degree of Mn2＋ on the surface of Mn-SC from 3.80 to 3.46. However, due to the formation of amorphous MnOx, the surface oxidation active sites for gaseous Hg0 increased, which gave Mn-H-SC higher mercury adsorption efficiency than that of Mn-SC at high temperature.

Carboniferous integrative stratigraphy and timescale of China

The Carboniferous period lasted about 60 Myr, from ～358.9 Ma to ～298.9 Ma. According to the International Commission on Stratigraphy, the Carboniferous System is subdivided into two subsystems, i.e., Mississippian and Pennsylvanian, including 6 series and 7 stages. The Global Stratotype Sections and Points(GSSPs) of three stages have been ratified, the Tournaisian, Visean, and Bashkirian stages. The GSSPs of the remaining four stages(i.e., the Serpukhovian, Moscovian,Kasimovian, and Gzhelian) have not been ratified so far. This paper outlines Carboniferous stratigraphic subdivision and correlation on the basis of detailed biostratigraphy mainly from South China, and summarizes the Carboniferous chronostratigraphic framework of China. High-resolution biostratigraphic study reveals 37 conodont zones, 24 foraminiferal(including fusulinid) zones, 13 ammonoid zones, 10 brachiopod zones, and 10 rugose coral zones in the Carboniferous of China. The biostratigraphic framework based on these biozones warrants the precise correlation of regional stratigraphy of China(including2 subsystems, 4 series, and 8 stages) to that of the other regions globally. Meanwhile, the Carboniferous chemo-, sequence-,cyclo-, and event-stratigraphy of China have been intensively studied and can also be correlated worldwide. Future studies on the Carboniferous in China should focus on(1) the correlation between shallow-and deep-water facies and between marine and continental facies,(2) high-resolution astronomical cyclostratigraphy, and(3) paleoenvironment and paleoclimate analysis based on geochemical proxies such as strontium and oxygen isotopes, as well as stomatal indices of fossil plants.

晚古生代大冰期碳-水循环回顾与展望

晚古生代大冰期(360~260 Ma)是地球上自动植物繁盛以来持续时间最长的冰期事件,记录了陆地自有高等植被和复杂陆地生态系统以来,唯一的一次从“冰室气候”向“温室气候”的转变.针对晚古生代大冰期的研究大多聚焦于全球碳循环以及冰川性海平面变化等方面,对大冰期的水循环研究相对较少,并且其主要基于气候模拟研究结果.随着单颗粒锆石精确测年技术的应用,高精度的综合地层框架使得冈瓦纳中高纬度地区冰川消长与低纬度地区沉积记录、生物多样性与演化及各种全球地球化学记录建立时序关系,为研究地球循环系统和反馈机制提供了基础条件.目前,对晚古生代大冰期碳同位素变化趋势已有较好认识,存在3次显著的碳同位素正漂事件,依次为杜内中期、巴什基尔早期和阿瑟尔早期,并且在时间上与冈瓦纳大陆识别的3次冰川高峰吻合.在宾夕法尼亚亚纪卡西莫夫末期发生了一次短暂的碳同位素负漂事件,引起显著的全球变暖和海洋缺氧.冰川体积与古热带区域气候动态在天文轨道周期尺度至1~8个百万年的冰期-间冰期时间尺度上都具有耦合关系.在各种时间尺度上,晚古生代大冰期地球表层系统各个圈层之间的反馈过程都非常复杂.因此,今后需在高精度综合地层框架下,开展不同复杂程度的生物地球化学循环和地球系统模型等的模拟工作,以全面地揭示晚古生代大冰期碳-水循环关联机制.

Microbially Induced Carbonate Precipitation in a Middle Triassic Microbial Mat Deposit from Southwestern China:New Implications for the Formational Process of Micrite

Lime mud(i.e.,micrite)is a major component of carbonate deposits.Various mechanisms(biotic versus abiotic)have been proposed for the formation of lime mud in Earth’s history.However,the detailed role that microbes play in the nucleation and subsequent precipitation of micrites remains to be resolved.Herein we undertook a detailed geobiological characterization of laminated lime mudstone from the Middle Triassic Guanling Formation in Yunnan Province,southwestern China.Morphological features,together with previous geobiological investigations,suggest that the laminated lime mudstones represent the former presence of microbial mats.These lime mudstones consist mainly of calcite,dolomite and quartz,with clay minerals and pyrites as subordinate components.In particular,micro-analysis shows copious nano-globules(65–878 nm)and capsule-shaped nano-rods in laminations.These low-Mg calcite nano-globule aggregates are closely associated with mucilaginous biofilms resembling extracellular polymeric substances(EPS).Nano-sized globules coalesce to form semi-euhedral micrite crystals.We suggest that a decaying hydrolytic destruction of the EPS by microbial communities within microbial mat leads to the precipitation of the nano-globules by enhancing alkalinity in local micro-environment.As an intermediate,these nano-globules further aggregate to form micrite crystals possibly through a dissolution-reprecipitation process.

Depositional Environments of the Upper Permian Quartzose Sandstone(Shandong Province, North China): Insight from Trace Element Geochemistry

The depositional environment of the Upper Permian quartzose sandstone （Kuishan sandstone in Shihezi Formation of Upper Permian） in the North China epicontinental basin is controversial. In order to test the previous hypotheses, we analyzed sedimentological characteristics of the Kuishan sandstones in outcrops and boreholes, and carried out trace element geochemical analysis by electron probe microanalyzer. Three lithofacies were recognized, including normal-graded conglomerate （Cng）, trough and planar cross-bedded coarse sandstone （CStpc）, and planar cross-bedded medium sandstone （MSpc）. Normal-graded conglomerate （Cng） formed in the meandering river or deltaic distributary channels. Trough and planar cross-bedded coarse sandstone （CStpc） formed in meandering river or distributary channels of near-source deltaic plain. Planar cross-bedded medium sandstone （MSpc） formed in the siliciclastic beach with highto moderate-energy conditions. By the petrology and trace elements analysis, three relatively large-scale transgressions were revealed. Each transgression was reflected by the lower content of Ba and ratios of Fe/Mn, and the high content of B and ratios of B/Ga. The ratios of Ni/Co of all samples are all lower than 2, suggesting oxygen-enriched shallower water en- vironment during deposition of the Kuishan sandstones.

High Li^(+)coordinated solvation sheaths enable high-quality Li metal anode

An advance Li-sphere possessing a definitely regular morphology in Li deposition enables a well-defined more robust structure and superior solid-electrolyte interphase(SEI)to achieve high-efficiency long-term cycles in Li metal anode.Here,a new sight of high Li^(+)cluster-like solvation sheaths coordinated in a localized high-concentration NO_(3)^(-)(LH-LiNO_(3))electrolyte fully clarifies for depositing advanced Li spheres.Moreover,we elucidate a critical amorphouscrystalline phase transition in the nanostructure evolution of Li-sphere deposits during the nucleation and growth.Li-sphere anode exhibits ultrastable structural engineering for suppressing Li dendrite growths and rendering ultralong life of 4000 cycles in symmetrical cells at 2 mAcm^(-2).The as-constructed Li spheres/3DCMjLiFePO_(4)(LFP)full cell delivers a high capacity retention of 90.5%at 1 C after 1000 cycles,and a robust dendrite-free structure also stably exists in Li-sphere anode.Combined with high-loading LFP cathodes(6.6 and 10.9 mg cm^(-2)),superb capacity retentions are up to 96.5%and 92.5%after 800 cycles at 1 C,respectively.Cluster-like solvation sheaths with high Li^(+)coordination exert significant influence on depositing a highquality Li-sphere anode.

Asymmetric double-layer composite electrolyte with enhanced ionic conductivity and interface stability for all-solid-state lithium metal batteries

All-solid-state Li metal battery has been regarded as a promising battery technology due to its high energy density based on the high capacity of lithium metal anode and high safety based on the all solid state electrolyte without inflammable solvent.However,challenges still exist mainly in the poor contact and unstable interface between electrolyte and electrodes.Herein,we demonstrate an asymmetric design of the composite polymer electrolyte with two different layers to overcome the interface issues at both the cathode and the anode side simultaneously.At the cathode side,the polypropylene carbonate layer has enough viscosity and flexibility to reduce the inter-facial resistance,while at the Li anode side,the polyethylene oxide layer modified with hexagonal boron nitride has high mechanical strength to suppress the Li dendrite growth.Owing to the synergetic effect between different components,the asprepared double layer composite polymer electrolyte demonstrates a large electrochemical window of5.17 V,a high ionic conductivity of 6.1×10~(-4) S/cm,and a transfe rence number of 0.56,featuring excellent ion transport kinetics and good chemical stability.All-solid-state Li metal battery assembled with LiFePO_4 cathode and Li anode delivers a high capacity of 150.9 mAh/g at 25℃ and 0.1 C-rate,showing great potential for practical applications.