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.     

Preparation of anhydrous magnesium chloride in a gas-solid reaction with ammonium carnallite

Dehydrated ammonium carnallite was synthesized with bischofite from salt lake and ammonium chloride solution in a 1:1 molar ratio of MgCl₂:NH₄Cl, dehydrated at 160°C for about 4 h. The yield was above 85%. The product was then mixed with solid-state ammonium chloride with a 1:4 mass ratio for the further dehydration at 410°C. The decomposition of NH₄Cl made a pressure of NH₃ at 30.5 kPa to prevent the hydrolysis of ammonium carnallite. The anhydration of magnesium chloride was achieved at 700°C. The results showed that anhydrous magnesium chloride contains magnesium oxide in an amount that was less than 0.1% by weight. XRD pattern and SEM micrograph showed a good dispersion of ammonium carnallite and anhydrous magnesium chloride crystals with well-distributed big grains, just enough to meet the need for the production of magnesium metal in the electrolysis process. __________ Translated from Chinese Journal of Applied Chemistry, 2005, 22(8) (in Chinese)     

有机溶剂法无水氯化镁的制备与表征

Ammonium carnallite was synthesized by hydrated magnesium chloride in salt lake and ammonium chloride solution. Dehydrated ammonium carnallite was dissolved in methanol under low temperature by feeding ammonia, to prepare anhydrous magnesium chloride. The results show that anhydrous magnesium chloride contains magnesium oxide in an amount less than 0.1% by weight, the yield of magnesium chloride was above 99.5%. Ammonium carnallite, ammoniation magnesium chloride and anhydrous magnesium chloride were characterized by thermoanalysis, X-ray powder diffraction and scanning electron microscopy.     

Investigation of the Reaction of Roasted Serpentine Ore with Some Ammonium Salts

The reaction between roasted serpentine ore and ammonium sulfate was studied at the range of temperature 250–1000°C using different molar ratios to determine the maximum extraction of magnesia and also to characterize the different reaction products. The maximum extraction of MgO from the roasted ore reached 92.4% at 400°C. It was found from XRD that ammonium magnesium sulfate [(NH₄)₂Mg₂(SO₄)₃] was produced as the main product at 400°C, which decomposes to magnesium sulfate at 500–600°C. The last compound decomposes to magnesium oxide at 900–1000°C. Thermal analysis of the reaction mixture confirmed the results obtained by XRD. Extraction of magnesia by ammonium chloride at 300–400°C showed low percentage of extraction (7.8%). Comparison was made between using ammonium chloride instead of sulfate taking into consideration the thermal decomposition products of both ammonium salts. Extraction of magnesia from the roasted ore by aqueous ammonium sulfate or ammonium chloride showed good results.     

微波辐照实现PVC-PS之间的Friedel-Crafts接枝反应

在四氢呋喃、环己酮等溶液中实现了聚氯乙烯(PVC)与聚苯乙烯(PS)的Friedel-Crafts接枝反应,考察了加热方式、反应温度、催化剂种类、催化剂用量对接枝反应的影响,通过FTIR表征了PVC-g-PS接枝物的结构,探讨了反应的机理和特点.研究发现,油浴加热和微波辐照都能使PVC和PS发生接枝反应,但微波辐照效果更好,油浴加热,接枝率仅0.27%,而微波辐照接枝率高达23%;油浴加热时产物少且多为间位,微波辐照时产物多且多为对位和邻位.无水AlCl3、无水FeCl3、无水SnCl4皆对PVC与PS之间的Friedel-Crafts反应具有催化活性,其中无水AlCl3的催化活性最高,其最佳用量为质量分数3%,此时,接枝率达到29%.当无水AlCl3过高时,PVC降解,产生双键,接枝率下降.表明微波辐照是实现PVC与PS之间Friedel-Crafts接枝反应的有效途径.     

聚二烯丙基甲基苄基氯化铵的合成及粘度行为

以甲胺、烯丙基氯、NaOH、氯化苄和偶氮二异丙基咪唑啉盐酸盐为原料,合成了聚二烯丙基甲基苄基氯化铵(PDAMABC),采用FT IR、1H NMR和元素分析对其结构进行表征,并考察了其在氯化钠、氯化钾、溴化钾、氯化钙、氯化镁、硫酸镁和硫酸钠溶液中的粘度行为。 将所得水相和低沸点馏分回用,二烯丙基甲基胺的收率从72.79%提高至83.41%;以水与乙醇为混合溶剂（V（H2O）∶V（C2H5OH）为1∶3~2∶3）,合成的二烯丙基甲基苄基氯化铵收率较高且水溶性好。 PDAMABC的比浓粘度随外加盐浓度增加而降低。 在0.1 mol/L NaCl溶液中,当其质量浓度低于0.031 25 g/L时,表现为聚电解质行为;质量浓度大于0.125 g/L时,表现为中性聚合物的粘度行为。 外加盐对比浓粘度的影响顺序为：Na2SO4＜NaCl＜KCl＜MgSO4＜MgCl2＜CaCl2＜KBr。 阴离子的屏蔽作用是导致比浓粘度降低的主要原因。     

气相色谱-三重四极杆质谱法快速检测鸡蛋中氟虫腈及其代谢物

建立了QuEChERS前处理技术结合气相色谱-三重四极杆质谱（GC-MS/MS）分析鸡蛋中氟虫腈及其代谢物的快速检测方法。样品由乙腈提取,然后经150 mg MgSO₄脱水和50 mg N-丙基乙二胺（PSA）、50 mg C18净化,采用农药残留专用柱（TR-Pesticide Ⅱ）进行气相色谱分离,以定时反应监测（timed-SRM）模式进行检测,基质曲线外标法定量。结果表明,氟虫腈及其代谢物在1.0~200 μg/L范围内呈良好线性,线性相关系数（R²）均大于0.999,定量限为0.5~1.0 μg/kg;氟虫腈及其代谢物在3个添加水平（2、5和10 μg/kg）下的加标回收率为87.8%~111.5%,相对标准偏差（RSD,n=3）为2.0%~9.2%,该方法能满足欧盟规定的鸡蛋中氟虫腈及其代谢物的残留检测限量要求。     

高效液相色谱-串联质谱法测定黄瓜、草莓中乙嘧酚和二甲嘧酚

建立了黄瓜、草莓中高效液相色谱-串联质谱同时检测乙嘧酚和二甲嘧酚残留的方法。样品加入乙腈高速匀浆,提取液中加入无水MgSO4和NaCl,振荡离心后,取上清液经分散固相萃取净化,液相色谱-串联质谱电喷雾正离子扫描同时分析乙嘧酚和二甲嘧酚。以黄瓜、草莓为基质进行3档添加水平和5次重复性实验,结果表明,添加量为0.01～1 mg/kg,乙嘧酚和二甲嘧酚的平均回收率为77.6%～99.3%,RSD为1.1%～6.8%,乙嘧酚和二甲嘧酚的方法检测限均为2.0μg/kg,定量限分别为6.0和5.0μg/kg。     

3-丙烯酰基-1,3-噁唑烷-2-酮的合成

3-α,β-不饱和酰基-1,3-噁唑烷-2-酮在烷基化及Diels-Alder等反应中在手性催化剂的存在下,产物都有较高的对映选择性。但3-丙烯酰基-3,3-噁唑烷-2-酮极易聚合,现有制备方法结果均不理想。本文将丙烯酸与丙烯酰氯在三乙胺的存在下生成酸酐,再在无水氯化锂的作用下与1,3-噁唑烷-2-酮在室温反应,反应结束后直接将反应混合物通过硅胶柱色谱进行层析分离得到3-丙烯酰基-1,3-噁唑烷-2-酮,产率达83％。合成路线如下：     

高效液相色谱法测定消毒湿巾中苯扎氯铵的含量

提出了高效液相色谱法测定消毒湿巾中苯扎氯铵含量的方法。样品经流动相超声提取,以Eclipse XDB-C18色谱柱(150 mm×4.6 mm,5μm)为分离柱,以乙腈-70 mmol.L-1乙酸铵(含1%三乙胺,冰乙酸调pH至5.0)按体积比70比30混合液为流动相,用二极管阵列检测器于波长262 nm处测定。苯扎氯铵的质量浓度在100～500 mg.L-1范围内与其峰面积呈线性关系,检出限(3S/N)为10.2mg.L-1。应用此法测定消毒湿巾中苯扎氯铵,回收率在95.3%～97.8%之间,相对标准偏差(n=5)在2.5%～4.0%之间。     

Determination of beryllium by means of hexamminecobalt(III) carbonatoberyllate—I Composition of the precipitate and its suitability as a weighing form for beryllium

The precipitate obtained when hexamminecobalt(III) chloride is added to a solution of beryllium in excess ammonium carbonate has been analysed and its behaviour under different humidity conditions examined. The composition is that of hexamminecobalt(III) hexacarbonato-oxo-tetraberyllate [Co(NH₃)₆]₂[Be₄O(CO₃)₆]·xH₂O, as suggested by Sen Gupta, rather than that of Pirtea [Co(NH₃)₆][(H₂O)₂ Be₂(CO₃)₂(OH)₃]·3H₂O.x depends on the humidity of conditioning, varying between 10.8 and 11.1 at relative humidities between 32 and 80%. Drying the precipitate in vacuo over anhydrous magnesium perchlorate or phosphorus pentoxide results in 3 molecules of water being retained. The compound as normally precipitated may be a mixture of the deca- and dodecahydrates that Sen Gupta prepared. After conditioning at a definite humidity and if an empirical factor is used, the precipitate may be suitable as a gravimetric form for determining beryllium where precision requirements are not too exacting.