Nanostructured MXene-based materials for boosting hydrogen sorption properties of Mg/MgH_(2)

Hydrogen holds the advantages of high energy density,great natural abundance and zero emission,making it suitable for large scale and long term energy storage,while its safe and efficient storage is still challenging.Among various solid state hydrogen storage materials,MgH_(2) is promising for industrial applications due to its high gravimetric and volumetric hydrogen densities and the abundance of Mg on earth.However,the practical application of MgH_(2) has been limited by its stable thermodynamics and slow hydrogen desorption kinetics.Nanocatalysis is considered as a promising approach for improving the hydrogen storage performance of MgH_(2) and bringing it closer to the requirements of commercial applications.It is worth mentioning that the recently emerging two-dimensional material,MXene,has showcased exceptional catalytic abilities in modifying the hydrogen storage properties of MgH_(2).Besides,MXene possesses a high surface area,excellent chemical/physical stability,and negatively charged terminating groups,making it an ideal support for the"nanoconfinement"of MgH_(2) or highly active catalysts.Herein,we endeavor to provide a comprehensive overview of recent investigations on MXene-based catalysts and MXene supports for improving the hydrogen sorption properties of Mg/MgH_(2).The mechanisms of hydrogen sorption involved in Mg-MXene based composites are highlighted with special emphases on thermodynamics,kinetics,and catalytic behaviors.The aim of this work is to provide a comprehensive and objective review of researches on the development of high-performance catalysts/supports to improve hydrogen storage performances of Mg/MgH_(2) and to identify the opportunities and challenges for future applications.

Effects of soaking process on arsenic and other mineral elements in brown rice

One of the main food crops in the world,rice can accumulate high levels of arsenic from flooded paddy soils,which seriously threatens human health.Soaking,a common processing method for brown rice products,especially for brown rice noodles,was investigated in this study.Japonica rice(Dao Hua Xiang No.2)and Indica rice(Ye Xiang You No.3)were selected for studying the effects of soaking on arsenic concentrations,species,and distributions.Results revealed that soaking can efficiently remove arsenic in these two rice varieties,and the main part of removal is endosperm with the maximal rate of about 40%.Inorganic arsenic(I-As)(about 85%)is the main species of arsenic reduction.Meanwhile,the variations of four other elements(i.e.,Mg,Ca,Zn,and Fe)were analyzed.Collectively,the findings of this study indicate that soaking can efficiently remove arsenic in brown rice under controlled soaking conditions,which thereby reduces the arsenic intake for brown rice customers.

厚壁结构聚碳酸酯制品注射成型的典型缺陷与控制

采用单因素多水平的试验方法,考察了注射成型工艺对厚壁结构聚碳酸酯制品的典型缺陷(表观缺陷、几何收缩和残余应力)的影响,工艺条件包括模具温度、注射速度、保压时间、保压压力和冷却时间。通过制品表观质量、收缩状态和应力分布的表征,分析了不同缺陷的变化规律。结果表明,表观缺陷中的真空泡在模具温度120℃以上、保压时间20 s、冷却时间60 s时基本不存在,而表面气痕在注射速度低于5 mm/s时完全消除。随着保压压力、保压时间和模具温度的增加,制品几何收缩显著降低,尺寸精度和几何变形得到有效控制。制品的残余应力受成型工艺的影响,但退火处理的影响更加明显,也是降低残余应力的有效手段。

注射成型后期热处理对聚碳酸酯性能的影响

考察了退火方式和退火工艺对聚碳酸酯(PC)残余应力和拉伸性能的影响。光弹法定量分析结果表明,退火能够显著降低PC的残余应力,残余应力随退火温度升高和退火时间延长而减小。但退火温度越高,退火温度和退火时间对PC残余应力影响差异性逐渐减弱。拉伸测试结果表明,130℃4 h退火工艺下,开模取件后立即退火使PC拉伸强度提高5.5%,而完全冷却后退火则使PC拉伸强度降低8.7%。综合分析表明,退火消除的流动残余应力将降低PC的拉伸强度,而退火消除的热残余应力则会提高PC的拉伸强度,退火过程中拉伸强度的变化,是流动残余应力和热残余应力偶合作用变化的结果。

Reversible lithium storage in sp^(2) hydrocarbon frameworks

Polymer materials offer controllable structure-dependent performances in separation,catalysis and drug release.Their molecular structures can be precisely tailored to accept Li^(+)for energy storage applications.Here the design of sp^(2)carbon-based polyphenylene(PPH)with high lithium-ion uptakes and long-term stability is reported.Linear-PPH(L-PPH)exceeds the performance of crosslink-PPH(C-PPH),due to the fact that it has an ordered lamellar structure,promoting the Li^(+)intercalation/deintercalation channel.The L-PPH cell shows a clear charge and discharge plateau at 0.35 and 0.15 V vs.Li^(+)/Li,respectively,which is absent in the C-PPH cell.The Li^(+)storage capacity of L-PPH is five times that of the C-PPH.The reversible storage capacity is further improved to 261 m Ah g;by functionalizing the L-PPH with the–SO_(3)H groups.In addition,the Li-intercalated structures of C-PPH and L-PPH are investigated via near-edge X-ray absorption fine structure(NEXAFS),suggesting the high reversible Li^(+)–C=C bond interaction at L-PPH.This strategy,based on new insight into sp^(2)functional groups,is the first step toward a molecular understanding of the structure storage-capacity relationship in sp^(2)carbon-based polymer.

Versatile memristor implemented in van der Waals CuInP_(2)S_(6)

Memristors are playing an increasingly important role in developing in-memory computing.Versatile memristors which offer both volatile and non-volatile performances can be employed as both memories and selectors,displaying unique advantages for developing novel electronic circuits.Herein,the remarkable multifunctional memristor with switchable operating modes between volatile and non-volatile by regulating compliance currents is implemented in Ag/CIPS/Au(CIPS:CuInP_(2)S_(6))device.Diode-like volatile memristor performances with the rectification ratio of 10^(3) and an endurance of 500 switching cycles were obtained.Meanwhile,significant non-volatile memory performances with on/off ratio of 10^(3)and retention up to 10^(4)s were also developed,which enables it to be utilized as selectors and memories simultaneously.Moreover,such versatile memristor can emulate the short-term plasticity(STP)and long-term plasticity(LTP)of artificial synapse,demonstrating its advantages in neuromorphic computing applications.

卤化物钙钛矿-分子筛复合材料的表面重构驱动晶格氧用于电催化水分解

可再生能源驱动的电催化分解水制氢是实现氢经济的有效途径,对实现“双碳”目标具有重要意义^([1~3]).然而,位于阳极的析氧半反应(OER)涉及多步的四电子转移,动力学缓慢,较高过电位的存在严重制约了电解水制氢的能量转换效率.目前,性能优异的阳极材料主要以贵金属基IrO_(2)和RuO_(2)催化剂为主,因此,研发具有高催化活性与优良稳定性的非贵金属催化剂是电解水制氢大规模应用面临的长期挑战^([4,5]).

Confining carbon dots in amino-functionalized mesoporous silica:n→π^(*) interaction triggered deep-red solid-state fluorescence

Deep-red and near-infrared emissive carbon dots(CDs)are highly desired for bioimaging,especially in deep tissue imaging,but they are extremely rare and the known ones usually suffer from low-efficient fluorescence in water and aggregation-induced fluorescence quenching in solid state.In this work,CDs with intriguing solvent-dependent and two-photon fluorescence emissions have been prepared by a facile solvothermal method.Detailed characterizations reveal that there is an n→π*interaction between the carboxyl functional groups on CDs and the electron donor groups in solvent,which leads to the increase of energy density of CDs and the decrease of energy level,resulting in the red shift of luminescence with enhanced electron donating ability of solvent.Inspired by this finding,mesoporous silica nanoparticles(MSNs)with suitable pore size and low biological toxicity are modified by amino groups to confine CDs,thus the deep-red fluorescence emission is achieved both in solid state and in water facilitated by the n→π*interaction of host-guest.The as-prepared CDs@EDA-MSN composite exhibits high-efficient fluorescence with 650 nm wavelength,low toxicity,and good biocompatibility,which endow them a promising application in bio-imaging.

Modulating hydrothermal condition to achieve carbon dots-zeolite composites with multicolor afterglow

Responsive luminescence materials with prolonged lifetime and multicolor emission have drawn great attention due to their attractive optical property and potential applications.Herein,two responsive carbon dots(CDs)based composites:CD_(1)@MCM-22P and CD_(2)@ZSM-12 were achieved by a one-step hydrothermal method.By adjusting the hydrothermal condition,CD_(1)@MCM-22P owns temperature-dependent afterglow,while CD_(2)@ZSM-12 is equipped with excitation-dependent room-temperature phosphorescence.The photoluminescence mechanisms of CD1@MCM-22P and CD_(2)@ZSM-12 were investigated and proposed,and the composites were applied in multi-mode anti-counterfeiting.This work provides an insight as well as a feasible method for the development of multi-emissive CDs@zeolite composite.

Urine biomarkers discovery by metabolomics and machine learning for Parkinson’s disease diagnoses

Parkinson’s disease(PD)is a complex neurological disorder that typically worsens with age.A wide range of pathologies makes PD a very heterogeneous condition,and there are currently no reliable diagnostic tests for this disease.The application of metabolomics to the study of PD has the potential to identify disease biomarkers through the systematic evaluation of metabolites.In this study,urine metabolic profiles of 215 urine samples from 104 PD patients and 111 healthy individuals were assessed based on liquid chromatography-mass spectrometry.The urine metabolic profile was first evaluated with partial leastsquares discriminant analysis,and then we integrated the metabolomic data with ensemble machine learning techniques using the voting strategy to achieve better predictive performance.A combination of 8-metabolite predictive panel performed well with an accuracy of over 90.7%.Compared to control subjects,PD patients had higher levels of 3-methoxytyramine,N-acetyl-l-tyrosine,orotic acid,uric acid,vanillic acid,and xanthine,and lower levels of 3,3-dimethylglutaric acid and imidazolelactic acid in their urine.The multi-metabolite prediction model developed in this study can serve as an initial point for future clinical studies.

Carbon Dots-in-Zeolite via In-Situ Solvent-Free Thermal Crystallization:Achieving High-Efficiency and Ultralong Afterglow Dual Emission

Organic afterglow materials are highly desirable for optoelectronic applications,but they usually suffer from complex preparation process,low quantum efficiency,and short lifetime due to the ultrafast deactivation of the highly active excited states involved.Here,we succeeded in achieving solventfree thermal syntheses of high-efficiency afterglow CDs@zeolite composite materials by simply grinding the solid raw materials of zeolite and precursor CDs at room temperature,followed by thermal crystallization.This method afforded maximum embedding of CDs into growing zeolite crystals,as well as strong host–guest interaction to surpass the nonradiative transition of CDs,thus producing composite materials with ultralong dual emission of thermally activated delayed fluorescence and room temperature phosphorescence with a record high lifetime of 1.7 and 2.1 s,respectively,and the quantum yield of 90.7%.Furthermore,in a preliminary experiment,we applied the composite materials in alternatingcurrent light-emitting diode supplementary lighting,which exhibited a promising potential in optoelectronic applications.

Direct laser patterning of two-dimensional lateral transition metal disulfide-oxide-disulfide heterostructures for ultrasensitive sensors

Two-dimensional(2D)heterostructures based on the combination of transition metal dichalcogenides(TMDs)and transition metal oxides(TMOs)have aroused growing attention due to their integrated merits of both components and multiple functionalities.However,nondestructive approaches of constructing TMD-TMO heterostructures are still very limited.Here,we develop a novel type of lateral TMD-TMO heterostructure(NbS2-Nb2O5-NbS2)using a simple lithography-free,direct laser-patterning technique.The perfect contact of an ultrathin TMO channel(Nb2O5)with two metallic TMDs(NbS2)electrodes guarantee strong electrical signals in a two-terminal sensor.Distinct from sensing mechanisms in separate TMOs or TMDs,this sensor works based on the modulation of surface conduction of the ultrathin TMO(Nb2O5)channel through an adsorbed layer of water molecules.The sensor thus exhibits high selectivity and ultrahigh sensitivity for room-temperature detection of NH3(ΔR/R=80%at 50 ppm),superior to the reported NH3 sensors based on 2D materials,and a positive temperature coefficient of resistance as high as 15%–20%/℃.Bending-invariant performance and high reliability are also demonstrated in flexible versions of sensors.Our work provides a new strategy of lithography-free processing of novel TMD-TMO heterostructures towards high-performance sensors,showing great potential in the applications of future portable and wearable electronics.

Lifetime-Engineered Phosphorescent Carbon Dots-in-Zeolite Composites for Naked-Eye Visible Multiplexing

Lifetime-coded optical multiplexing has attracted wide attention due to avoiding spectral overlap and background interference.At present,most of the materials used for lifetime-coded multiplexing involve rare-earth metal ions with their lifetime domains in the microsecond range,thus greatly limiting their application scope.

Robust photoluminescence energy of MoS_2/graphene heterostructure against electron irradiation

Two-dimensional （2D） materials have attracted growing attention since the discovery of graphene [1]. Transition metal dichalcogenide （TMD） semiconductors, such as MoS2 and WS2, became popular materials in recent years, because they usually have intrinsic bandgaps and an in- direct-to-direct bandgap transition from bulk to mono- layer limit [2-6]. Although graphene and TMDs are promising materials in field-effect devices [7-9], their heterostructures are more advanced in charge-splitting functions for the applications in optoelectronic devices [10-15].

Photoluminescent chiral carbon dots derived from glutamine

The integration of luminescence and chirality in carbon dots(CDs) encourages candidates to explore novel functions and applications of CDs, however, the preparation of chiral CDs is very limited. Herein, we report a hydrothermal method to fabricate chiral CDs by utilizing amino acid enantiomers as the precursors. LGln-CDs or DGln-CDs with uniform size of 3–4 nm show excitation-dependent blue fluorescence in solutions. Circular dichroism measurement confirms the opposite optical rotation of chiral CDs in the region from 200 nm to 300 nm, and the signals can be regulated by concentrations of CDs solution. Timedependent density functional calculation reveals that polypeptides may exist on the surface of CDs due to the polycondensation of L/DGln at high temperature, and the optical activity of CDs originates from the stacking of neighboring carbonyl groups. The facile synthetic methodology proposed will provide potential opportunities for the preparation and application of chiral and chiroptical CDs-based materials.

Calcination-controlled fabrication of carbon dots@zeolite composites with multicolor fluorescence and phosphorescence

In light of the exceptional optical qualities,luminous carbon dots(CDs),particularly those with room-temperature phosphorescence(RTP),have a wide range of applications in a variety of fields.However,modulating afterglow emissions practically and efficiently remains a serious difficulty.Herein,a feasible strategy of calcination combined with in-situ synthesis is proposed to fabricate CDs-based composites with multicolor fluorescence(FL)and phosphorescence.Through pre-selection of small pore RHO zeolite as a matrix,CDs have been successfully embedded due to strong guest–host interaction achieved by insitu hydrothermal synthesis.By the unique pore architecture and excellent stability of the zeolite matrix,the surface oxidation degree and the carbon core size of confined CDs are engineered by temperature-controlled calcination.The resulting composites exhibit tunable FL(from 416 to 566 nm)and RTP(from 440 to 585 nm)in solid and aqueous solution,in which rarely occurring deep blue RTP is observed with a lifetime as long as 573 ms.Furthermore,the universality of such a calcination-modulated luminescent method has been proved by the AFI zeolite matrix.This study offers up a new way to regulate the luminescence of CDs facilitated by matrix,which considerably promotes the potential applications of CDs-based composites in the future.

The power of comments： fostering social interactions in microblog networks

Today＇s ubiquitous online social networks serve multiple purposes, including social communication （Face- book, Renren）, and news dissemination （Twitter）. But how does a social network＇s design define its functionality？ An- swering this would need social network providers to take a proactive role in defining and guiding user behavior. In this paper, we first take a step to answer this question with a data-driven approach, through measurement and anal- ysis of the Sina Weibo microblogging service. Often com- pared to Twitter because of its format, Weibo is interesting for our analysis because it serves as a social communication tool and a platform for news dissemination, too. While similar to Twitter in functionality, Weibo provides a distinguishing feature, comments, allowing users to form threaded con- versations around a single tweet. Our study focuses on this feature, and how it contributes to interactions and improves social engagement. We use analysis of comment interactions to uncover their role in social interactivity, and use comment graphs to demonstrate the structure of Weibo users interac- tions. Finally, we present a case study that shows the impact of comments in malicious user detection, a key application on microblogging systems. That is, using properties of com- ments significantly improves the accuracy in both modeling and detection of malicious users.