MXene Key Composites:A New Arena for Gas Sensors

With the development of science and technology,the scale of industrial production continues to grow,and the types and quantities of gas raw materials used in industrial production and produced during the production process are also constantly increasing.These gases include flammable and explosive gases,and even contain toxic gases.Therefore,it is very important and necessary for gas sensors to detect and monitor these gases quickly and accurately.In recent years,a new two-dimensional material called MXene has attracted widespread attention in various applications.Their abundant surface functional groups and sites,excellent current conductivity,tunable surface chemistry,and outstanding stability make them promising for gas sensor applications.Since the birth of MXene materials,researchers have utilized the efficient and convenient solution etching preparation,high flexibility,and easily functionalize MXene with other materials to pre-pare composites for gas sensing.This has opened a new chapter in high-performance gas sensing materials and provided a new approach for advanced sensor research.However,previous reviews on MXene-based composite materials in gas sensing only focused on the performance of gas sensing,without systematically explaining the gas sensing mechanisms generated by different gases,as well as summarizing and predicting the advantages and disadvantages of MXene-based composite materials.This article reviews the latest progress in the application of MXene-based composite materials in gas sensing.Firstly,a brief summary was given of the commonly used methods for preparing gas sens-ing device structures,followed by an introduction to the key attributes of MXene related to gas sensing performance.This article focuses on the performance of MXene-based composite materials used for gas sensing,such as MXene/graphene,MXene/Metal oxide,MXene/Transition metal sulfides(TMDs),MXene/Metal-organic framework(MOF),MXene/Polymer.It summarizes the advantages and disadvantages of MXene com-posite materials with different composites and discusses the possible gas sensing mechanisms of MXene-based composite materials for different gases.Finally,future directions and inroads of MXenes-based composites in gas sensing are presented and discussed.

A novel“Snowflake”--rGO-CuO for ultrasonic degradation of rhodamine and methyl orange

Graphene-doped CuO(rGO-CuO)nanocomposites with flower shapes were prepared by an improved solvothermal method.The samples were characterized by X-ray diffraction,X-ray photoelectron spectroscopy and UV–visible spectroscopy.The active species in the degradation reaction of rGO-CuO composites under ultrasonic irradiation were detected by electron paramagnetic resonance.On the basis of comparative experiments,the photodegradation mechanisms of two typical dyes,Rhodamine B(Rh B)and methyl orange(MO),were proposed.The results demonstrated that the doped CuO could improve the degradation efficiency.The catalytic degradation efficiency of rGO-CuO(2:1)to rhodamine B(RhB)and methyl orange(MO)reached 90%and 87%respectively,which were 2.1 times and 4.4 times of the reduced graphene oxide.Through the first-principles and other theories,we give the reasons for the enhanced catalytic performance of rGO-CuO:combined with internal and external factors,rGO-CuO under ultrasound could produce more hole and active sites that could interact with the OH·in pollutant molecules to achieve degradation.The rGO-CuO nanocomposite has a simple preparation process and low price,and has a high efficiency of degrading water pollution products and no secondary pollution products.It has a low-cost and high-efficiency application prospect in water pollution industrial production and life.

A Rising 2D Star:Novel MBenes with Excellent Performance in Energy Conversion and Storage

As a flourishing member of the two-dimen-sional(2D)nanomaterial family,MXenes have shown great potential in various research areas.In recent years,the continued growth of interest in MXene derivatives,2D transition metal borides(MBenes),has contributed to the emergence of this 2D material as a latecomer.Due to the excellent electrical conductivity,mechanical properties and electrical properties,thus MBenes attract more researchers’interest.Extensive experimental and theoretical studies have shown that they have exciting energy conversion and elec-trochemical storage potential.However,a comprehensive and systematic review of MBenes applications has not been available so far.For this reason,we present a comprehen-sive summary of recent advances in MBenes research.We started by summarizing the latest fabrication routes and excellent properties of MBenes.The focus will then turn to their exciting potential for energy storage and conversion.Finally,a brief summary of the challenges and opportunities for MBenes in future practical applications is presented.

Ultrasound application in alkaline pretreatment process of spodumene to improve particle floatability

Selective surface dissolution was found to be important in spodumene flotation. In this study, we proposed to introduce ultrasound into the pretreatment process to accelerate particle vibration and cavitation, as well as the migration of mineral surface components to solution. Micro-flotation results showed that the flotation recovery of spodumene can be 86.08% by ultrasound pretreatment, but only 39.30% by traditional mechanical agitation pretreatment. Compared with traditional mechanical agitation, ultrasonic pretreatment can shorten the pretreatment process, reduce the dosage of agents, reduce the mechanical agitation speed, and improve the efficiency of the pretreating process. Inductively coupled plasma analysis showed that, in the ultrasonic system, the amount of Li, Al, and Si species in the solution was twice as much as those in the traditional preprocessing system. Moreover, the scanning electron microscope results demonstrated a larger surface dissolution area in the ultrasonic system. X-Ray photoelectron spectroscopy results showed that the atomic concentration of Si species on the spodumene surface decreased, whereas the relative atomic concentrations of Li and Al species increased, indicating that the ultrasound effect strengthened the selective dissolution of elements on the mineral surface.The high-resolution spectra of O 1s showed that more collectors are adsorbed on the mineral surface treated by ultrasonic pretreatment.

MXene Ti_(3)C_(2) decorated g-C_(3)N_(4)/ZnO photocatalysts with improved photocatalytic performance for CO_(2) reduction

Photocatalytic reduction of CO_(2) is considered as a kind of promising technologies for solving the greenhouse effect.Herein,a novel hybrid structure of g-C_(3)N_(4)/ZnO/Ti_(3)C_(2) photocatalysts was designed and fabricated to investigate their abilities for CO_(2) reduction.As demonstration,heterojunction of g-C_(3)N_(4)/ZnO can improve photogenerated carriers’separation,the addition of Ti_(3)C_(2) fragments can further facilitate the photocatalytic performance from CO_(2) to CO.Hence,g-C_(3)N_(4)/ZnO/Ti_(3)C_(2) has efficiently increased CO production by 8 and 12 times than pristine g-C_(3)N_(4) and ZnO,respectively.Which is ascribed to the photogenerated charge migration promoted by metallic Ti_(3)C_(2).This work provides a guideline for designing efficient hybrid catalysts on other applications in the renewable energy fields.

Metabolic analyses reveal different mechanisms of leaf color change in two purple-leaf tea plant (Camellia sinensis L.) cultivars

Purple-leaf tea plants,as anthocyanin-rich cultivars,are valuable materials for manufacturing teas with unique colors or flavors.In this study,a new purple-leaf cultivar“Zixin”(“ZX”)was examined,and its biochemical variation and mechanism of leaf color change were elucidated.The metabolomes of leaves of“ZX”at completely purple,intermediately purple,and completely green stages were analyzed using ultra-performance liquid chromatography quadrupole time of flight mass spectrometry(UPLC-QTOF-MS).Metabolites in the flavonoid biosynthetic pathway remained at high levels in purple leaves,whereas intermediates of porphyrin and chlorophyll metabolism and carotenoid biosynthesis exhibited high levels in green leaves.In addition,fatty acid metabolism was more active in purple leaves,and steroids maintained higher levels in green leaves.Saponin,alcohol,organic acid,and terpenoid-related metabolites also changed significantly during the leaf color change process.Furthermore,the substance changes between“ZX”and“Zijuan”(a thoroughly studied purple-leaf cultivar)were also compared.The leaf color change in“Zijuan”was mainly caused by a decrease in flavonoids/anthocyanins.However,a decrease in flavonoids/anthocyanins,an enhancement of porphyrin,chlorophyll metabolism,carotenoid biosynthesis,and steroids,and a decrease in fatty acids synergistically caused the leaf color change in“ZX”.These findings will facilitate comprehensive research on the regulatory mechanisms of leaf color change in purple-leaf tea cultivars.

Preparation, characterization and catalytic performance of single-atom catalysts

Supported and colloidal single‐atom catalysts(SACs),which possess excellent catalytic properties,are particularly important in both fundamental studies and practical applications.The progress made in the preparation methods,characterization,catalytic performances and mechanisms of SACs anchored to metal oxides,two‐dimensional materials and the surface of metal nanoclusters(NCs)are reviewed.The different techniques for SAC fabrication,including conventional solution methods based on co‐precipitation,incipient wetness co‐impregnation,and the chemical vapor deposition method,as well as the newer atom layer deposition(ALD)and galvanic replacement methods,are summarized.The main results from experimental and theoretical studies of various catalytic reactions over SACs,including oxidation reactions,hydrogenation,water gas shift,photocatalytic H2evolution and electrochemical reactions,are also discussed.Moreover,the electronic properties of the single atoms and their interactions with the supports are described to assist in understanding the origin of the high catalytic activity and selectivity of SACs.Finally,possible future research directions of SACs and their applications are proposed.

Vital roles for ethnobotany in conservation and sustainable development

The scientific discipline of ethnobotany-the study of human interactions with plants e has applications in many fields of current global concern,including food security,climate change,biodiversity conservation and human health.Ethnobotanical studies can provide insights into the ways that societies interact locally with their environmental resources.Ethnobotanical studies have the potential to bring together and integrate local and scientific knowledge to advance the cause of achieving biocultural conservation(Gaoue et al.,2017;Prance,2007).This Special Issue of Plant Diversity contains recent ethnobotanical studies that aim to contribute to determining the most useful ways ethnobotany can be used to confront human problems in the future.Specifically,this issue shows ways in which ethnobotany can contribute to the conservation of biodiversity,especially with regards to documentation and maintenance of indigenous and local knowledge of plants.The research in this issue also describes innovative practices communities have adopted to maintain their plant resources。

Crystal structure and optical performance analysis of a new type of persistent luminescence material with multi-functional application prospects

Persistent luminescence (PersL) materials,as environmentally friendly and energy-saving materials,have broad application prospects in many fields such as lighting,chemistry and even biomedicine.However,studies on the types,performances and mechanism of PersL materials are still insufficient,which significantly restricts their development and application.Under this consideration,we successfully synthesized a yellow PersL material CaSrGa_(4)O_(8)(CSG).The crystal structure was studied in detail through Rotation Electron Diffraction (RED) and Powder X-ray Diffraction (PXRD).What’s more,by co-doping Mn^(2+) and Yb^(3+),the afterglow brightness of CSG could be increased by nearly 20 times,and the afterglow duration could reach more than 6 h.It is worth mentioning that the samples also have excellent performances in mechanical luminescence (ML),photostimulated luminescence (PSL) and cathodoluminescence (CL),which was also investigated systematically.Finally,an anti-counterfeiting label was designed by the samples to reveal the potential of their application in anti-counterfeiting.The results showed that our research not only provided a new candidate PersL material for multifunctional applications,but also gave good help for studying the physical and chemical properties of CSG.

Ethnobotanical survey of plants traditionally used against hematophagous invertebrates by ethnic groups in the mountainous area of Xishuangbanna, Southwest China

Hematophagous invertebrates such as mosquitoes,leeches,mites,ticks,lice and bugs cause various problems for humans.Considering reports on insecticide resistance and requirements for improved environmental and toxicological profiles,there is a continuing need to discover and develop new insecticides and repellents.Ethnobotanical surveys of traditional plant-based repellents provide a direct method of identifying plants for potential use.During five field surveys in Bulang,Jinuo and Lahu villages between August 2018 and July 2019,semi-structured interviews were conducted with 237 informants(151 male,86 female;mean age 63).Frequency of citation,use value,informant consensus factor and Jaccard index were employed to statistically analyze the collected data.A total of 709 use reports relating to 32 plant species and 71 remedies were collected.Similarities and differences between the three groups,as well as the Dai and Hani of Xishuangbanna,who were studied earlier,were shown through network analysis.These five ethnic groups living in the same area have a common understanding of traditional botanical knowledge against hematophagous invertebrates,but each group also possesses unique knowledge.Recording and protecting this traditional knowledge is potentially useful for protecting this cultural diversity and related biodiversity and can also have important practical applications.In this study,traditional knowledge provided us with many new potential plants for follow-up research for the development of new insecticides and repellents,among which Artemisia indica,Nicotiana tabacum and Clausena excavata are the most promising.

Photocatalyst with Chloroplast-like Structure for Enhancing Hydrogen Evolution Reaction

Photosynthesis with the chloroplast works efficiently because of the envelope structure that serves to carry enzymes and to simultaneously maintain the spatial separation of photosynthesis and cellular respiration.Inspired by the spatially separated architecture,a chloroplast-like structured photocatalyst(PdS@CdS@MoS_(2)),in which the PdS and MoS_(2) function as enzymes in the chloroplast and CdS shell functions as the chloroplast envelope,was developed to improve the photocatalytic H_(2) evolution.In this unique nanoscale bionic structure,the poriferous CdS shell enhances light absorption,generates photoinduced carriers,and separates oxidation and reduction reactions.Meanwhile,PdS and MoS_(2) dual cocatalysts enhance the charge separation efficiency through forming a built-in electric field with CdS.We demonstrate that the separation efficiency of carriers,carrier lifetime,and the yield of H_(2) are both higher than that of CdS nanoparticles,evidencing the feasibility of the chloroplast-like structure in enhancing the photocatalyst activity.This work emphasizes the synergism of the three key processes of the photocatalytic reaction by simulating the chloroplast structure and provides a general synthesis strategy,the synthesis of novel structured for photocatalysts for diverse applications in the energy field.

Native useful vascular plants of China:A checklist and use patterns

Of all types of interactions between humans and plants,the utilization of plants by people is the most direct and influential.China has a long history of using native plants and a large body of recorded knowledge on uses.Here,we present an inventory of plant uses in China based on an extensive survey of the literature.Twelve categories of usage are recognized(medicinal,edible,etc.),these categories being chosen according to an integration of various current standards.A total of 50,521 use-citations were recorded,covering 10,808 species and infraspecies,representing 28%of the Chinese flora.Additional information is included in the dataset on taxonomy and endangerment status.Analysis of the data reveals that the eight plant families with the greatest numbers of species used in China,namely Asteraceae,Fabaceae,Rosaceae,Ranunculaceae,Poaceae,Lamiaceae,Orchidaceae,and Liliaceae,are also the top eight most species-rich Chinese plant families.However,there are some families that are overrepresented or under-representation in certain use categories,compared with their relative abundance in the total flora.There are indications that rare and endangered species are being subject to some degree of over-exploitation.A disproportionately high number of used species are Chinese endemics(3552 species,representing over 33%of used species).A total of 20%of used species have been classified as threatened nationally or globally,according to at least one of the various threat assessments that have been made for the Chinese flora.This comprehensive inventory of the useful plants of China,with relevant ethnobotanical information included,provides a baseline for further studies of plant resources.It will be useful in follow-up research.The scientific dataset it contains will be useful for the protection and sustainable utilization of plant resources in China.

Genome-wide analysis of microRNAs induced and regulated by colchicine in mulberry

A variety of plants were colchicine treated to double their chromosome number.Chromosomes are genetic carriers that determine the individual traits of organisms.The doubling of chromosomes will lead to modifications in plant morphology,physiology and genetics.To determine the response of mulberry trees induced by colchicine,using mulberry variety Yu-711 leaves as research materials,two small RNA libraries(control and experimental groups)were constructed.It was found that 45 known miRNA genes and 78 predicted novel miRNA genes in the sequence results.A comparison of data between the control group and the experimental group revealed 37 differentially expressed miRNA genes,19 genes of which were up-regulated and 18 genes of which were down-regulated.Eight miRNAs were selected from 37 differentially expressed miRNA genes.These miRNAs were verified by quantitative real-time PCR,and the expression levels of these miRNAs were found to be consistent with those obtained by sequencing,which proved the accuracy of sequencing results.The PsRNATarget software was used to predict the target genes of 8 miRNAs.The Gene Ontology and Kyoto Encycopedia of Genes and Genomes analysis were used to collect the functions of target genes and confirm that target genes are mainly involved in biological processes,cell components and molecular functions.novel-77 miRNA was selected from 37 differentially expressed miRNAs.What will serve as a fundamental data in understanding mulberry miRNAs function in molecular biology research and further provides the molecular mechanism of mulberry gene regulation as induced by colchicine is that the prediction of novel_77 precursor sequence and the target gene(XM_010104258.2),as well as the secondary structure analysis.

Passivated ZnSe nanocrystals prepared by hydrothermal methods and their optical properties

Homogeneous Zn Se nanocrystals were prepared via surfactant-assisted hydrothermal method.Surfactants agent CTAB was used to control the particle morphology and the growth rate.The structure,morphology and optical properties of Zn Se nanocrystals have been investigated by XRD,TEM and luminescence spectroscopy.The results indicated that the size of Zn Se nanocrystals ranged from 3.0 nm to 5.0 nm with cubic zinc blende structure.Zn Se nanocrystals coated by CTAB were revealed high dispersibility and distribution under TEM.Compared to the bulk Zn Se,the absorption edges and photoluminescence peaks of Zn Se nanocrystals were blue shifted to higher energies due to the quantum confinement effect.The emission intensity was strengthened after coated CTAB compared to bare sample.This was mainly due to the surface passivation.Meanwhile,we simply explored the formation mechanism of Zn Se nanocrystal in hydrothermal system.

Effects of Roudoukou-8 San Extract on Hydrogen Peroxide Induced Cardiomyocyte Injury

[Objectives] To study the effects of Roudoukou-8 San extract on hydrogen peroxide( H_2O_2) induced cardiomyocyte injury of rats and explore its action mechanism. [Methods] The cardiomyocytes of neonatal rats were isolated and cultured,and the H_2O_2 induced cardiomyocyte injury model was established. Methyl thiazolyl tetrazolium( MTT) assay was used to detect the protective effects of Roudoukou-8 San extract on H_2O_2 induced cardiomyocyte. The effects of Roudoukou-8 San on cardiomyocyte morphology were observed under inverted microscope. The contents of lactate dehydrogenase( LDH),creatine kinase( CK) and aspartate aminotransferase( AST) in cell culture medium were determined by automatic biochemical instrument; the levels of malondialdehyde( MDA),superoxide dismutase( SOD) and nitric oxide( NO) in the cells were detected by kit method. The apoptotic morphology of cardiomyocytes was observed by Hoechst fluorescence staining.Cell apoptosis were measured by Annexin V and PI double staining and flow cytometer. [Results]100 μmol/L of H_2O_2 acting 2 h could cause about 50% of cardiomyocyte injury. H_2O_2 model group showed increased cell gap,decreased cell count,cell cytoplasmic vacuoles and other obvious damages. Compared with H_2O_2 model group,in Roudoukou-8 San extract dose groups,cardiomyocyte morphology showed different degrees of improvement,Roudoukou-8 San extract can significantly reduce the content of LDH,CK and AST in H_2O_2 injured myocardial cell culture solution,significantly reduce content of MDA and NO in H_2O_2 injured myocardial cells,increase the SOD activity,and significantly inhibit the apoptosis of H_2O_2 injured myocardial cells. [Conclusions]Through improving the cell survival status,increasing the cell viability,reducing oxidative stress injury,inhibiting inflammatory responses,and inhibiting apoptosis,Roudoukou-8 San extract can improve the state of H_2O_2 induced cardiomyocyte injury,so as to protect H_2O_2 injured myocardial cells.

MMLUP: Multi-Source & Multi-Task Learning for User Profiles in Social Network

With the rapid development of the mobile Internet,users generate massive data in different forms in social network every day,and different characteristics of users are reflected by these social media data.How to integrate multiple heterogeneous information and establish user profiles from multiple perspectives plays an important role in providing personalized services,marketing,and recommendation systems.In this paper,we propose Multi-source&Multi-task Learning for User Profiles in Social Network which integrates multiple social data sources and contains a multi-task learning framework to simultaneously predict various attributes of a user.Firstly,we design their own feature extraction models for multiple heterogeneous data sources.Secondly,we design a shared layer to fuse multiple heterogeneous data sources as general shared representation for multi-task learning.Thirdly,we design each task’s own unique presentation layer for discriminant output of specific-task.Finally,we design a weighted loss function to improve the learning efficiency and prediction accuracy of each task.Our experimental results on more than 5000 Sina Weibo users demonstrate that our approach outperforms state-of-the-art baselines for inferring gender,age and region of social media users.

Lipopolysaccharide Attenuates CD40 Ligand-Induced Regulatory B10 Cell Expansion and IL-10 Production in Mouse Splenocytes

Toll-like receptors (TLRs) play a key role in B cell-mediated innate and adaptive immunity. It has been shown that interleukin 10 (IL-10)-producing regulatory B cells (B10 cells) can negatively regulate cellular immune responses and inflammation in autoimmune diseases. In this study, we determined the effect of TLR4 signaling on the CD40-activated B10 cell competency. The results demonstrated that LPS and CD40L synergistically stimulated proliferation of mouse splenocytes. The percentage of B10 cells in cultured splenocytes was significantly increased after CD40L stimulation but such increase was diminished by the addition of LPS. Such effects by LPS were only observed in cells from WT but not TLR4−/−mice. IL-10 mRNA expression and protein production in B10 cells from cultured splenocytes were significantly up-regulated by CD40L stimulation but were inhibited after the addition of LPS in a TLR4-dependent manner. This study suggests that LPS-induced TLR4 signaling attenuate CD40L-activated regulatory B10 cell competency.

Selecting flagship species to solve a biodiversity conservation conundrum

The difficulty of effectively monitoring and managing the environment to conserve biodiversity is as yet an unsolved conundrum.A project of the Chinese Academy of Sciences has concluded that progress can be made through the use of flagship species selected using criteria drawn from conservation biology,ecosystem function,socio-economics,and cultural importance.Inclusion of the latter three criteria will help attract and maintain the commitment of the public to play full parts in carrying out any conservation measures needed.A system is proposed for scoring species to select those that are most suitable as flagships.This method can be used regardless of the size of the area chosen for attention,whether it is a region,a country,or a particular protected area.

Electrical stimulation for brighter persistent luminescence

An immature understanding of the mechanisms of persistent luminescence(PersL)has hindered the development of new persistent luminescent materials(PersLMs)with increased brightness.In this regard,in-situ direct current(DC)electric field measurements were conducted on a layered structure composed of the SrAl_(2)O_(4):Eu^(2+),Dy^(3+)phosphor,and an electrode.In this study,the photoluminescence(PL)and afterglow properties were investigated with respect to voltage by analyzing the current signal and thermoluminescence(TL)spectroscopy.The intensity of PersL increased due to a novel phenomenon known as“external electric field stimulated enhancement of initial brightness of afterglow”.This dynamic process was illustrated via the use of a rate equation approach,where the electrons trapped by the ultra-shallow trap at 0.022 eV could be transferred through the conduction band during long afterglow.The afterglow intensity could reach 0.538 cdm^(-2)at a 6 V electric voltage.The design of an electric field stimulation technique enables the enhancement of the intensity of PersLMs and provides a new perspective for exploring the fundamental mechanics of certain established PersLMs.

碳构造:一个地球系统科学新范式

地球系统科学是一门复杂性科学,迄今没有一个简单理论完整解释地球系统行为.碳构造既是地球系统运行的一种新模式,也是一种研究新范式,其基本构成有碳泵、碳传送带及碳开关.碳泵是跨圈层物质能量垂向交换机制,碳传送带则是同一圈层内的水平输送机制,碳开关控制着地球系统运行状态和进化方向.碳构造是多学科研究地球系统的突破口和交叉点.