Miniaturized electrochemical sensors and their point-of-care applications

Most of the current analytical methods depend largely on laboratory-based analytical techniques that require expensive and bullky equipment,potentially incur costly testing,and involve lengthy detection processes.With increasing requirements for point-of-care testing(POCT),more attention has been paid to miniaturized analytical devices.Miniaturized electrochemical(MEC)sensors,including different material-based MEC sensors(such as DNA-,paper-,and screen electrode-based),have been in strong demand in analytical science due to their easy operation,portability,high sensitivity,as well as their short analysis time.They have been applied for the detection of trace amounts of target through measuring changes in electrochemical signal,such as current,voltage,potential,or impedance,due to the oxidation/reduction of chemical/biological molecules with the help of electrodes and electrochemical units.MEC sensors present great potential for the detection of targets including small organic molecules,metal ions,and biomolecules.In recent years,MEC sensors have been broadly applied to POCT in various fields,including health care,food safety,and environmental monitoring,owing to the excellent advantages of electrochemical(EC)technologies.This review summarized the state-of-the-art advancements on various types of MEC sensors and their applications in POCT.Furthermore,the future perspectives,opportunities,and challenges in this field are also discussed.     

Machine Learning towards Screening Solid-state Lithium Ion Conductors

Machine learning is an emerging method to discover new materials with specific characteristics.An unsupervised machine learning research is highlighted to discover new potential lithium ionic conductors by screening and clustering lithium compounds,providing inspirations for the development of solid-state electrolytes and practical batteries.     

Surface defect-rich ceria quantum dots anchored on sulfur-doped carbon nitride nanotubes with enhanced charge separation for solar hydrogen production

Designing defect-engineered semiconductor heterojunctions can effectively promote the charge carrier separation.Herein,novel ceria(CeO2) quantum dots(QDs) decorated sulfur-doped carbon nitride nanotubes(SCN NTs) were synthesized via a thermal polycondensation coupled in situ depositionprecipitation method without use of template or surfactant.The structure and morphology studies indicate that ultrafine CeO2 QDs are well distributed inside and outside of SCN NTs offering highly dispersed active sites and a large contact interface between two components.This leads to the promoted formation of rich Ce³⁺ ion and oxygen vacancies as confirmed by XPS.The photocatalytic performance can be facilely modulated by the content of CeO2 QDs introduced in SCN matrix while bare CeO2 does not show activity of hydrogen production.The optimal catalyst with 10% of CeO2 loading yields a hydrogen evolution rate of 2923.8 μmol h-1 g-1 under visible light,remarkably higher than that of bare SCN and their physical mixtures.Further studies reveal that the abundant surface defects and the created 0 D/1 D junctions play a critical role in improving the separation and transfer of charge carriers,leading to superior solar hydrogen production and good stability.     

Superfast and solvent-free core-shell assembly of sulfur/carbon active particles by hail-inspired nanostorm technology for high-energy-density Li-S batteries

The demand on low-carbon emission fabrication technologies for energy storage materials is increasing dramatically with the global interest on carbon neutrality.As a promising active material for metal-sulfur batteries,sulfur is of great interest due to its high-energy-density and abundance.However,there is a lack of industry-friendly and low-carbon fabrication strategies for high-performance sulfur-based active particles,which,however,is in critical need by their practical success.Herein,based on a hail-inspired sulfur nano-storm(HSN)technology developed in our lab,we report an energy-saving,solvent-free strategy for producing core-shell sulfur/carbon electrode particles(CNT@AC-S)in minutes.The fabrication of the CNT@AC-S electrode particles only involves low-cost sulfur blocks,commercial carbon nanotubes(CNT)and activated carbon(AC)micro-particles with high specific surface area.Based on the above core-shell CNT@AC-S particles,sulfur cathode with a high sulfur-loading of 9.2 mg cm^-2 delivers a stable area capacity of 6.6 mAh cm^-2 over 100 cycles.Furthermore,even for sulfur cathode with a super-high sulfur content(72 wt%over the whole electrode),it still delivers a high area capacity of 9 mAh cm^-2 over50 cycles in a quasi-lean electrolyte condition.In a nutshell,this study brings a green and industryfriendly fabrication strategy for cost-effective production of rationally designed S-rich electrode particles.     

Unraveling the stabilization mechanism of solid electrolyte interface on ZnSe by rGO in sodium ion battery

Transition metal selenides have been widely studied as anode materials of sodium ion batteries(SIBs),however,the investigation of solid-electrolyte-interface(SEI)on these materials,which is critical to the electrochemical performance of SIBs,remains at its infancy.Here in this paper,ZnSe@C nanoparticles were prepared from ZIF-8 and the SEI layers on these electrodes with and without reduced graphene oxide(rGO)layers were examined in details by X-ray photoelectron spectroscopies at varied charged/discharged states.It is observed that fast and complicated electrolyte decomposition reactions on ZnSe@C leads to quite thick SEI film and intercalation of solvated sodium ions through such thick SEI film results in slow ion diffusion kinetics and unstable electrode structure.However,the presence of rGO could efficiently suppress the decomposition of electrolyte,thus thin and stable SEI film was formed.ZnSe@C electrodes wrapped by rGO demonstrates enhanced interfacial charge transfer kinetics and high electrochemical performance,a capacity retention of 96.4%,after 1000 cycles at 5 A/g.This study might offer a simple avenue for the designing high performance anode materials through manipulation of SEI film.     

CXN天然沸石的研究2: 吸附性质

采用N~2,NH~3,CO~2,乙烯,丙烯,水,甲醇,乙醇,丙醇等作为吸附剂,研究了由我国CXN天然沸石改性制得的H-STI和Na-STI沸石的吸附性质,H-STI和Na-STI沸石的BET表面积及微孔孔体积约为420m^2/g和0.20m^3/g。根据NH~3和CO~2在H-STI沸石上的吸附等温线计算得到它们的吸附热分别为44.8和26.5kJ/mol。乙烯,丙烯,甲醇,乙醇,丙醇等在Na-STI沸石上的吸附等温线表明该沸石对有机分子的吸附具有链长选择性。在低分压下水相对于甲醇的吸附量表明沸石具有一定的疏水性质。     

常温常湿条件下Au/MeO~x催化剂上CO氧化性能

利用共沉淀法制备了Au/MeO~x催化剂(Me=Al,Co,Cr,Cu,Fe,Mn,Ni,Zn)。在常温常湿条件下,考察了不同氧化物负载的金基催化剂的CO氧化性能。结果表明,氧化物种类对催化剂的活性和稳定性均有较大的影响。Cu,Mn,Cr等氧化物负载的金基催化剂的活性较差,而Zn,Fe,Co,Ni,Al等金属氧化物负载的金基催化剂可将CO完全氧化,又具有一定的稳定性,在相同反应条件下,CO完全转化时的稳定性顺序为Au/ZnO>Au/α-Fe~2O~3>Au/Co~3O~4>Au/γ-Al~2O~3≈Au/NiO。还发现水对Au/MnO~x催化剂的活性和稳定性有负作用,而对180℃焙烧制备的Au/ZnO-180催化剂的活性和稳定性均有明显的湿度增强作用。     

Regulation of carbon distribution to construct high-sulfur-content cathode in lithium-sulfur batteries

Lithium-sulfur(Li-S)battery is regarded as one of the most promising next-generation energy storage systems due to the ultra-high theoretical energy density of 2600 Wh kg^-1.To address the insulation nature of sulfur,nanocarbon composition is essential to afford acceptable cycling capacity but inevitably sacrifices the actual energy density under working conditions.Therefore,rational structural design of the carbon/sulfur composite cathode is of great significance to realize satisfactory electrochemical performances with limited carbon content.Herein,the cathode carbon distribution is rationally regulated to construct high-sulfur-content and high-performance Li-S batteries.Concretely,a double-layer carbon(DLC)cathode is prepared by fabricating a surface carbon layer on the carbon/sulfur composite.The surface carbon layer not only provides more electrochemically active surfaces,but also blocks the polysulfide shuttle.Consequently,the DLC configuration with an increased sulfur content by nearly 10 wt%renders an initial areal capacity of 3.40 mAh cm^-2 and capacity retention of 83.8%during 50 cycles,which is about two times than that of the low-sulfur-content cathode.The strategy of carbon distribution regulation affords an effective pathway to construct advanced high-sulfur-content cathodes for practical high-energy-density Li-S batteries.     

Boost oxygen reduction reaction performance by tuning the active sites in Fe-N-P-C catalysts

Cost-effective atomically dispersed Fe-N-P-C complex catalysts are promising to catalyze the oxygen reduction reaction(ORR)and replace Pt catalysts in fuel cells and metal-air batteries.However,it remains a challenge to increase the number of atomically dispersed active sites on these catalysts.Here we report a highly efficient impregnation-pyrolysis method to prepare effective ORR electrocatalysts with large amount of atomically dispersed Fe active sites from biomass.Two types of active catalyst centers were identified,namely atomically dispersed Fe sites and Fe_xP particles.The ORR rate of the atomically dispersed Fe sites is three orders of magnitude higher than it of Fe_xP particles.A linear correlation between the amount of the atomically dispersed Fe and the ORR activity was obtained,revealing the major contribution of the atomically dispersed Fe to the ORR activity.The number of atomically dispersed Fe increases as the Fe loading increased and reaching the maximum at 1.86 wt%Fe,resulting in the maximum ORR rate.Optimized Fe-N-P-C complex catalyst was used as the cathode catalyst in a homemade Zn-air battery and good performance of an energy density of 771 Wh kgZn^-1,a power density of 92.9 m W cm^-2 at 137 m A cm^-2 and an excellent durability were exhibited.     

The pseudocapacitance mechanism of graphene/CoAl LDH and its derivatives:Are all the modifications beneficial?

Cobalt-Aluminum layered double hydroxide(CoAl LDH) is a hopeful electrode material due to the advantage of easy modifiability for preparing LDH-based derivatives.However,there is short of modification methods to prepare the Co-based derivatives from CoAl LDH and also short of an intuitive perspective to analyze the pseudocapacitance mechanism of CoAl LDH and its derivatives.Herein,Graphene/CoAl LDH and its derivatives including Graphene/CoS,Graphene/CoS-1,Graphene/CoOOH,Graphene/CoP were prepared by reasonably using alkali etching treatment,sulfofication and phosphorization.The specific capacitance of Graphene/CoAl LDH,Graphene/CoS,Graphene/CoS-1,Graphene/CoOOH,Graphene/CoP at1 A g^-1 are 260.7,371.3,440.8,61.4 and 122.2 F g^-1,especially.The pseudocapacitance mechanism of Graphene/CoAl LDH and its derivatives was analyzed.Due to the positive effect of sulfofication on the electrical conductivity of GO and cobalt sulfide,the Graphene/CoS and Graphene/CoS-1 exhibit the optimal electrochemical performance and superior rate capability.In addition,due to the repulsion effect between Graphene and OH-,the Graphene/CoAl LDH exhibits optimal cycling stability of 224.1% capacitance retention after 20000 cycles.Besides,the reason of terrible specific capacitance of Graphene/CoOOH is that the presence of H bond in interlayer of CoOOH inhibits the interaction between Co3+ and OHspecies.Hence,not all modifications will increase the specific capacitance of the electrode materials.Overall,this work provides us with a detailed analysis of the electrochemical mechanism and correlation of CoAl LDH and its derivatives from the perspective of crystal structure and composition.     

Cun、Agn和Aun(n≤9)团簇的静电极化率

The static polarizabilities and polarizability anisotropies of Cun,Agn and Aun (n≤9)clusters have been calculated by the B3LYP density functional method,which is a three parameter mixture of density functional and"exact" Hartree Fock exchange. The calculated results are compared with experimental polarizabilities of sodium clusters. It is shown that the size dependency of the static polarizabilities per atom of Cun,and Agn clusters possesses the same trend as that observed in sodium clusters exception of the Aunclusters while the polarizability of Au atom is much smaller than these of Cu and Ag.The(α-)of Au atom is the smallest and the(α-)per atom of Au approach to the values of Cu from the dimmer to the hexamer. It indicates that in Au clusters the electrons are more strongly attracted by the nuclei because of the more electrons. However,the absolute polarizabilities of the noble mental clusters are considerably smaller than those of the sodium clusters and the electronic structures of the noblemental are much more compact.     

Effect of Ag on the Grain Growth and Dielectric Properties of PbTiO3

A series of Ag-PbTiO3 composites were synthesized, and the effects of silver on the morphological development of hydrothermal synthesized PbTiO3 particles and dielectric properties of PbTiO3 ceramic were investigated. Results show that the introduction of Ag benefits the crystal growth of PbTiO3. The diffusion of Ag+ into the perovskite accelerates the crystal growth of PbTiO3 and leads to large fine PbTiO3 crystal. Furthermore, the dielectric constant of PbTiO3-based ceramic was enhanced greatly by the percolation effect of inner Ag clusters.     

Development of enzyme technology and enzyme engineering in China

Enzymes have been utilized in China for thousands of years for the production of various foods and alcoholic beverages. Today China manufactures and uses enzymes for not only the traditional areas of application, but is expanding the use of enzymes for a variety of nonfood areas. This report describes the present state of the art of enzyme manufacture and application in China today.     

Thermodynamics of dissolving and solvation processes for benzoic acid and the toluic acids in aqueous solution

Experimental data are presented for the solubility in water of benzoic and toluic acids from 5° to 65°C. From the solubility the molality of the monomeric form of the acid is calculated using literature data for both ionization and dimerization of the acid. These data for the monomer combined with data from the literature for vaporization of the solid and ionization in both the gas phase and the aqueous phase yield entropy and enthalpy changes for the solvation of molecular and anionic forms of the acid. A similar procedure is also applied to literature data for the solubility of benzene in water. It is shown that the hydration entropies of the monomeric forms are a linear function of their partial molar volumes. It is concluded that hydration of the undissociated o-toluic acid may be crucial to the increased acidity of that acid compared to benzoic acid.     

The (3+2)- and formal (3+3)-cycloadditions of N-vinylpyrroles with cyclic nitrones and C,N-cyclic azomethine imines

The addition of Lewis acids changes the path of the reaction of N-vinylpyrroles with 3,4-dihydroisoquinoline-N-oxides: formal (3 + 3)-cycloaddition proceeds instead of (3 + 2)-cycloaddition. In the case of benzoyl(3,4-dihydroisoquinolin-2-ium-2-yl)amides, reaction path does not change in the same conditions, but changing of the diastereoselectivity occurs and other diastereomer of (3 + 2)-cycloaddition became predominant.     

由合成气制备C_2含氧化合物用铑基催化剂中各组分间的相互作用

采用ＴＰＲ，ＥＰＲ，ＩＲ，ＸＰＳ等手段对由合成气制备Ｃ２含氧化合物的Ｒｈ基催化剂中各活性组分间的相互作用进行了研究．ＴＰＲ实验表明，Ｍｎ的存在除了促进金属铑在担体表面的分散，增加还原过程的耗氢量外，还使Ｒｈ物种的还原温度显著升高；少量Ｌｉ的加入导致氢向载体ＳｉＯ２的溢流，使体系的还原特性发生了明显的变化．原位ＥＰＲ和ＸＰＳ研究显示，添加剂与Ｒｈ相互作用，在催化剂表面形成了稳定的复合氧化物．助剂Ｍｎ主要起着吸引电子的作用，使还原后的催化剂表面上Ｒｈ＋物种的含量增加；相反，作为给电子助剂，Ｌｉ的加入稳定了表面Ｒｈ０物种．吸附ＣＯ的ＩＲ实验得到了与ＥＰＲ和ＸＰＳ实验相一致的结论     

超临界二氧化碳中不同聚合物吸附小分子的比较

研究了超临界二氧化碳中聚氨酯,乙烯醋酸乙烯共聚物和低密度聚乙烯等3种聚合物对几种小分子的吸附作用,观测了吸附小分子后的聚合物的形态变化以及无水乙醇和乙酸乙酯在这3种聚合物中的解吸,实验表明低密度聚乙烯吸附能力较差,不适作吸附的基体材料,而聚氨酯,乙烯醋酸乙烯共聚物吸附小分子能力较强。小分子在聚合物中按时间的自然指数形式递减规律解吸,解吸扩散系数数量级达10-7cm2/s。     

水稻秸秆与PVC塑料共气化过程中钾、钠、氯的迁移行为

采用固定床反应器,结合X射线衍射(XRD)表征和热力学计算研究了水稻秸秆与PVC塑料共气化过程中钾钠氯的迁移和状态变化。结果表明,混合物中氯的释放率与反应温度和PVC塑料的量(氯含量)有关。当反应温度为800~900℃时,PVC的量对混合物中氯元素释放率的影响最为显著;气化温度达900℃时,含PVC 20%(氯含量为11.5%)的水稻秸秆混合物中,氯元素的释放率较纯水稻上升了16.5%。与此同时,氯含量的增加也促进了钾钠在气相中的释放。气化温度为850℃时,当混合物中PVC比例大于20%(氯含量大于11.5%)时,氯对钾钠的气相析出有一定抑制作用;钾钠以KCl和NaCl的形式滞留在固相中,其含量随着混合物中PVC量的升高而降低。     

The effect of coating on the stiffness and toughness of encapsulated fiber composites

The effect of the coating of the fiber on the stiffness and toughness of composite materials is presented in this paper. The type of composite material considered is of a macroscopically isotropic composite medium containing coated fibers. The models used to simulate such materials consists of: the cylindrical fiber, a cylindrical annulus of the coating, an annulus of the matrix enveloped by an infinite region of an equivalent composite consisting of a transversely isotropic material and representing the real composite with dispersed coated fibers. Solutions for the longitudinal, transverse and shear elastic moduli in the four-phase model were established assuming linear elastic conditions. The results were found to depend on the extent and the mechanical properties of the coating. The stiffness and toughness of the composite were evaluated in models representing plane-stress equatorial sections of the representative volume element of the real material according to the Hashin-Rosen model. The stiffness of the fiber composites was studied by varying the rigidity and the extent of the fiber-coating in the model and evaluating its influence on the overall mechanical behavior of the model. On the other hand, the toughness of the composite was evaluated by the method of caustics in models made of composite PMMA plates with PMMA inclusions coated with a ductile annulus. Interesting results were derived concerning the influence of the soft annulus on the mechanical behavior of the composite.     

反相微乳液模板原位聚合制备纳米氯化银/聚甲基丙烯酸甲酯及其结构表征

用甲基丙烯酸甲酯(MMA)作油相,反相胶束微乳液作为模板,制备了纳米氯化银(AgCl)粒子,再进行原位聚合制备了纳米氯化银/聚甲基丙烯酸甲酯(AgCl/PMMA)复合材料.透射电镜(TEM)分析表明,纳米AgCl的尺寸为20～80 nm.扫描电镜(SEM)测试表明纳米AgCl粒子均匀地存在于PMMA基材中.红外分析证明,胶束中水和表面活性剂AOT的羰基在MMA聚合后微观环境发生变化,纳米粒子同聚合物之间有吸附行为.动态力学(DMTA)分析复合材料,发现纳米AgCl粒子与聚合物之间存在强烈相互作用,形成了中间相层(interphase layer),改变了聚合物的动态力学性能.