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。     

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.     

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.     

Confined Ni-In intermetallic alloy nanocatalyst with excellent coking resistance for methane dry reforming

Carbon dioxide and methane are two main greenhouse gases which are contributed to serious global warming.Fortunately,dry reforming of methane(DRM),a very important reaction developed decades ago,can convert these two major greenhouse gases into value-added syngas or hydrogen.The main problem retarding its industrialization is the seriously coking formation upon the nickel-based catalysts.Herein,a series of confined indium-nickel(In-Ni)intermetallic alloy nanocatalysts(In_xNi@SiO₂)have been prepared and displayed superior coking resistance for DRM reaction.The sample containing 0.5 wt.%of In loading(In_0.5Ni@SiO₂)shows the best balance of carbon deposition resistance and DRM reactivity even after 430 h long term stability test.The boosted carbon resistance can be ascribed to the confinement of core–shell structure and to the transfer of electrons from Indium to Nickel in In-Ni intermetallic alloys due to the smaller electronegativity of In.Both the silica shell and the increase of electron cloud density on metallic Ni can weaken the ability of Ni to activate C–H bond and decrease the deep cracking process of methane.The reaction over the confined InNi intermetallic alloy nanocatalyst was conformed to the Langmuir-Hinshelwood(L-H)mechanism revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy(in-situ DRIFTS).This work provides a guidance to design high performance coking resistance catalysts for methane dry reforming to efficiently utilize these two main greenhouse gases.     

微量热法研究硒对大肠杆菌生长代谢的作用

硒 是生物必需的微量元素之一．自从１９７３年Ｒｏｔｒｕｃｋ报导了第一个硒酶———红细胞谷胱甘肽过氧化物酶［１］,硒在生命科学中的研究取得了令人瞩目的进展．继红细胞谷胱甘肽过氧化物酶之后 ,从哺乳动物中还发现硒为多种酶所必需 ;此外 ,在不同的动物组织中一系列含硒蛋白被分离和鉴别．随着分子生物学技术的发展和硒在生物化学中的应用 ,人们对硒的生物化学本质有了更加深刻的认识 ,其中 ,遗传基因硒代半胱氨酸密码子ＵＧＡ的发现使硒的生物化学研究进入了一个新的阶段．与此同时 ,小分子有机硒化合物Ｅｂｓｅｌｅｎ生物活性的发现…     

重组质粒对大肠杆菌HB101生长影响的微量热研究

用微量热方法研究了嗜麦芽假单胞菌AT18, 受体菌大肠杆菌HB101, mel基因工程菌——大肠杆菌HB101/pWSY8和携带克隆载体pUC18质粒的大肠杆菌HB101等的生长代谢过程. 实验结果从热化学和热动力学上阐明了细菌的生长速率常数与其所含质粒的大小呈负相关. 探讨了低温处理对含不同质粒大肠杆菌生长的影响, 发现低温处理对工程菌生长影响最大.     

以对苯二甲酸为手臂连接剂的大肠杆菌DNA传感器

将空心球状CdS超声分散于聚乙烯醇(PVA)溶液中, 得到均匀的CdS-PVA复合材料分散液. 取适量分散液滴涂于玻碳电极表面, 晾干得到CdS-PVA修饰电极. 以对苯二甲酸为手臂连接剂, 在CdS-PVA膜上共价固定大肠杆菌特定寡聚核苷酸序列, 构建了一种新型的DNA传感器. 采用电化学阻抗法考察了该传感器的分析性能, 结果表明该传感器能有效区分互补序列、 单碱基错配序列、 三碱基错配序列和完全错配序列, 可在1.0×10^-12～1.0×10^-7 mol/L范围内对大肠杆菌目标序列进行定量分析, 检出限为1.3×10^-13 mol/L. 将该传感器应用于大肠杆菌实际样品的检测, 结果令人满意.     

Fabrication of microbial chip using collagen gel microstructure

A microbial chip was fabricated by filling the micropores on a glass substrate with collagen-embedded Escherichia coli(E. coli) cells, and characterized by scanning electrochemical microscopy (SECM) in a solution containing ferricyanide. The activity of the E. coli cells in the collagen gel microstructure was imaged and characterized with SECM by mapping the localized concentration of ferrocyanide produced by the respiration of the cells. The SECM-based activity measurement detected as low as approximately 100 E. coli cells. Furthermore, the optical-microscopic observation indicated that the E. coli cells on the chip proliferated during the incubation. The sequential SECM measurements were performed for the same E. coli chip to obtain the microbial growth curve for a small number of microorganisms.     

Role of nonadsorbing polymers in bacterial aggregation

Bacteria exhibit properties similar to those of nonbiological colloids and can display pairwise attractions when in close proximity. This interaction is governed by the surface chemistry of the cells. We seek to understand bacterial aggregation at the cellular level using Escherichia coli (E. coli) AB1157. Aggregation studies were carried out using 0.5 to 2.5 wt% E. coli AB1157 harvested in different growth phases with varying concentrations of a nonadsorbing polymer, sodium polystyrene sulfonate (SPS). The electrophoretic mobility of E. coli AB1157 in different growth phases was determined using phase-amplitude light scattering. E. coli AB1157 was found to be negatively charged, and the cell surface properties changed in different growth phases. The electrokinetic results correlated well with the different concentrations of nonadsorbing polymer needed to induce depletion aggregation. This shows that a difference in aggregation properties is due to changes in the bacteria electrokinetic properties during their growth.     

Aggregation behavior and size of lipopolysaccharide from Escherichia coli O55:B5

Dynamic light scattering, steady-state fluorescence, NMR diffusometry and cryo-TEM have been used to gain more insight into the aggregation behaviour of LPS from Escherichia coli O55:B5. Knowledge of this behaviour of the amphiphilic LPS molecule is in many cases of importance for the design of experiments and interpretation of results when using LPS in solution. The aim of this work was to study the aggregation and determine the aggregate size of E. coli O55:B5. The mean hydrodynamic radius of the LPS aggregates was determined by NMR diffusometry and dynamic light scattering to 14 and 26nm, respectively. The cryo-TEM technique revealed predominately spherical aggregates of 9-19nm. We wish to report 10mug/ml as the aggregation start for LPS E. coli O55:B5 in PBS buffer, pH 7.2. We suggest that the aggregation is a continuous process that starts at 10mug/ml and proceeds up to 300mug/ml.     

Cellular compatibility of biomineralized ZnO nanoparticles based on prokaryotic and eukaryotic systems

Zinc oxide nanoparticles (NPs) with the size of ～100 nm were prepared via a facile biomineralization process in the template of silk fibroin (SF) peptide at room temperature. These ZnO NPs have shown the remarkable behavior of low toxicity to gram-positive bacteria (Staphylococcus aureus, Staphylococcus agalactiae), gram-negative bacteria (Escherichia coli), and eukaryotic cells (mouse L929 fibroblasts). Bacteriological testing indicated that ZnO NPs presented a 50% inhibitory effect on Streptococcus agalactiae at the concentrations of >100 mM, whereas at the same concentrations, the growth of Staphylococcus aureus and Escherichia coli were hardly inhibited. On the other hand, a remarkable proliferation of Staphylococcus aureus or Escherichia coli was observed at the concentrations of ZnO NPs <50 mM. Moreover, the cytotoxicity test demonstrated that ZnO NPs mineralized with SF peptide possessed a low toxicity to mouse L929 fibroblasts. The SF peptide coated on the surface of ZnO NPs permitted greater adhesion and consequently greater proliferation of mouse L929 fibroblasts. Besides, from TEM micrographs of the cell ultrastructure, endocytosis of NPs into the cytoplasm can be detected and the ultrastructure of the cell underwent few changes. The cell membrane retained integrity, euchromatin dispersed homogenously inside the cytoplasm, the mitochondrial architecture remained intact, and no intracellular vacuoles were observed. High-resolution transmission electron microscopy images and selected area electron diffraction patterns of ultrathin cell sections indicated that the crystal structure of NPs was not damaged by the organelle or cytoplasm. All these observations indicated that ZnO NPs mineralized with the SF peptide possess good cytocompatibility.     

Facile preparation of antibacterial polymer coatings via thiol-yne click photopolymerization

Novel antibacterial polymer coatings were prepared by a facile thiol-yne click photopolymerization of 1-propargyl-3-alkyl-1,3-diazanyl-2,4-cyclopentadiene bromide ([PAIM]Br) and tetra(3-mercapto-propionate) pentaerythritol (PETMP) (2:1 molar ratio) using 2,2-dimethoxy-2-phenylacetophenone (DMPA) as initiator. The antibacterial activity of the coatings was tested against Staphylococcus aureus (ATCC 292130) and Escherichia coli (ATCC 25922) by the dynamic shake method. The evaluation results revealed the antibacterial polymer coatings exhibited excellent inhibitory activity against S. aureus and E. coli, especially for S. aureus.     

糖脂功能化聚二乙炔Langmuir-Schaefer薄膜与大肠杆菌的分子识别及动力学过程研究

在气液界面上研究了α-D-甘露糖苷-十六烷(MC₁₆)与10,12-二十五碳双炔酸混合单分子膜行为,二者具有较好的互溶性.在疏水的玻璃衬底上用Langmuir-Schaefer(LS)薄膜技术制备单层MC₁₆/PDA薄膜,研究了这种仿生薄膜与大肠杆菌jm109的相互作用.大肠杆菌jm109对MC₁₆修饰的聚二乙炔LS薄膜的吸附,使薄膜颜色由蓝色变为红色,用紫外-可见吸收光谱可进行定量检测.动力学研究显示比色响应值随时间的增加而增加,3min内即有显著变化,15min后趋于饱和,20min后CR值达到28%,进一步探讨了分子识别的动力学过程.     

Fura-2荧光探针研究Ca2+对大肠杆菌细胞的跨膜作用

以Fura-2／AM作为荧光探针,研究了Ca^2 对大肠杆菌HB101细胞的跨膜作用．考察了不同浓度外源钙离子处理不同生长时期细胞的跨膜行为,并采用停流技术测定了荧光动力学．结果表明大肠杆菌在用CaCl2溶液处理后,胞外Ca^2 可大量进入胞内,且进入细胞的钙离子量与胞外钙离子浓度相关;处于对数生长前期的细胞与对数生长后期和稳定期的细胞相比,胞内自身Ca^2 浓度低,但其摄取外源Ca^2 的能力最强,这应该与其生理代谢活性是相关的,而且这一时期是大肠杆菌细胞最易建立人工诱导感受态的时期．该研究对于测定革兰氏阴性菌细胞内Ca^2 浓度及胞外离子的跨膜传导行为,以及探索钙离子诱导的大肠杆菌人工感受态建立的生理机制都具有重要意义．