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.     

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。     

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。     

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.     

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.     

Enhanced visible-light-driven photocatalytic activities of 0D/1D heterojunction carbon quantum dot modified CdS nanowires

Zero-dimensional carbon dots (0D C-dots) and one-dimensional sulfide cadmium nanowires (1D CdS NWs) were prepared by microwave and solvothermal methods, respectively. A series of heterogeneous photocatalysts that consisted of 1D CdS NWs that were modified with 0D C-dots (C-dots/CdS NWs) were synthesized using chemical deposition methods. The mass fraction of C-dots to CdS NWs in these photocatalysts was varied. The photocatalysts were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. Their photocatalytic performance for the spitting of water and the degradation of rhodamine B (RhB) under visible light irradiation were investigated. The photocatalytic performance of the C-dots/CdS NWs was enhanced when compared with that of the pure CdS NWs, with the 0.4% C-dots/CdS NWs exhibiting the highest photocatalytic activity for the splitting of water and the degradation of RhB. The enhanced photocatalytic activity was attributed to a higher carrier density because of the heterojunction between the C-dots and CdS NWs. This heterojunction improved the electronic transmission capacity and promoted efficient separation of photogenerated electrons and holes.     

铜掺氧化锌多孔纳米棒的水热合成及其光催化性能

通过两步法合成铜掺杂的氧化锌纳米棒,通过X射线衍射（XRD）、扫描电子显微镜（FESEM）、透射电子显微镜（TEM）、X射线光电子能谱（XPS）和紫外-可见（UV-Vis）分光光谱等技术对系列样品进行了表征,研究并探索了铜掺杂的氧化锌纳米棒光降解染料罗丹明B（RhB）和气体乙醛的催化活性。通过对多孔Cu掺杂ZnO纳米棒光催化分解乙醛进行了评价。多孔Cu掺杂ZnO纳米棒（CZ-5）光催化剂具有最高的催化分解乙醛的能力,比其它多孔Cu掺杂ZnO纳米棒具有很高的催化活性。多孔Cu掺杂ZnO纳米棒光催化剂在室温下在可见光（435 nm）下照射16 h,5.50×10^-4（φ,体积分数）的乙醛气体完全降解为二氧化碳（CO₂）。多孔铜掺杂的氧化锌纳米棒光催化剂的光催化性能的改善主要归因于铜和氧化锌纳米棒之间的协同作用。这种改进的光催化协同作用归因于Cu掺杂ZnO的可见光吸收的延伸和光生电子空穴对的抗重组。     

Au纳米粒子负载的ZnO空心球复合材料的光生电荷转移行为及光催化活性

通过简单的两步法合成了不同负载量的Au/ZnO空心球。采用扫描电子显微镜(SEM),X射线衍射(XRD),X射线光电子能谱(XPS)及紫外-可见漫反射光谱(UV-Vis DRS)对样品的形貌、结构、组成和晶相等进行一系列的表征。以罗丹明B (RhB)为目标降解物,探究了Au/ZnO空心球的光催化活性。结果表明,适量Au修饰的ZnO光催化剂在混合光下20 min内对RhB的降解率达到73%。利用表面光电压谱(SPS)和瞬态光电压(TPV)技术,探讨了Au修饰后对ZnO光诱导电荷转移行为与光催化性能之间的关系。结果表明,混合光照下Au/ZnO空心球光降解性能的提高主要归因于作为电子受体的Au纳米粒子与ZnO之间形成的强的电子相互作用。适量Au纳米粒子的负载能够提高ZnO空心球中光生载流子的分离效率,相应地延长载流子的传输时间,增加光生电荷的寿命,从而促进其光催化活性的提高。     

ZnO/BiOI微球的合成及其光催化性能

通过一步溶剂热法合成ZnO/BiOI纳米复合材料,在Bi（NO₃）₃·6H₂O、KI、ZnO和乙二醇（EG）溶剂中,制备出的样品尺寸和形貌采用X射线粉末衍射（XRD）、场发射扫描电镜（FESEM）、高分辨透射电镜（HRTEM）、紫外-可见漫反射光谱（DRS）、X射线光电子能谱（XPS）、N₂吸附-脱附等,对实验所得产物的组成、结构及光学性质等进行表征。以染料罗丹明B（RhB）水溶液和气态乙醛作为降解对象,采用BiOI、ZnO/BiOI和ZnO微纳材料作为光催化剂,通过对BiOI、ZnO/BiOI和ZnO微纳材料在可见光下光催化降解染料罗丹明B（RhB）水溶液和气态乙醛,结果表明多孔微纳材料的ZnO/BiOI具有更高的降解效率,实验表明多孔微纳材料的ZnO/BiOI具有更高的氧空位浓度,因此使其催化活性增强,讨论了其可能的催化活性机理。     

ZnO/BiOI微球的合成及其光催化性能

通过一步溶剂热法合成ZnO/BiOI纳米复合材料,在Bi（NO₃）₃·6H₂O、KI、ZnO和乙二醇（EG）溶剂中,制备出的样品尺寸和形貌采用X射线粉末衍射（XRD）、场发射扫描电镜（FESEM）、高分辨透射电镜（HRTEM）、紫外-可见漫反射光谱（DRS）、X射线光电子能谱（XPS）、N₂吸附-脱附等,对实验所得产物的组成、结构及光学性质等进行表征。以染料罗丹明B（RhB）水溶液和气态乙醛作为降解对象,采用BiOI、ZnO/BiOI和ZnO微纳材料作为光催化剂,通过对BiOI、ZnO/BiOI和ZnO微纳材料在可见光下光催化降解染料罗丹明B（RhB）水溶液和气态乙醛,结果表明多孔微纳材料的ZnO/BiOI具有更高的降解效率,实验表明多孔微纳材料的ZnO/BiOI具有更高的氧空位浓度,因此使其催化活性增强,讨论了其可能的催化活性机理。     

水热pH值对溴氧化铋组成、形貌及光催化性能的影响

通过调节pH值一步水热法制备溴氧化铋光催化剂,并利用X射线衍射（XRD）、扫描电镜（SEM）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征。在可见光（γ>420 nm）照射下,通过对水溶液中罗丹明B,甲基橙和苯酚的降解效果来评价溴氧化铋的光催化活性。结果表明,由于B9提高了对可见光的吸收以及电子-空穴对的分离效率,B9具有最好的光催化活性,同时探索水热pH值对制备溴氧化铋的形貌和组成的影响,并说明了不同水热pH值下溴氧化铋的合成过程。     

LaCoO3晶格结构内外Mg的同步改性及其光催化性能

运用溶胶-凝胶法同步获得了LaCoO₃钙钛矿晶格结构内Mg²⁺的掺杂改性及晶格结构外MgO的异质结复合改性。观察到了同步改性后LaCoO₃催化剂上水体罗丹明B（RhB）光催化降解活性的显著提升,相同实验条件下最适Mg含量改性LaCoO₃上RhB的降解率从原始LaCoO₃的58%显著提升至98%,表观一级动力学常数为改性前催化剂的4.5倍。运用X射线衍射（XRD）、氮气低温吸附-脱附（BET法）、扫描及透射电子显微镜（SEM,TEM）、傅里叶变换红外光谱（FT-IR）、X光电子能谱（XPS）、紫外-可见漫反射（DRS）及光致发光光谱（PL）等分析和表征系统探讨了改性前后催化剂的理化特征。结果表明,约10% Co³⁺晶格结点可为Mg²⁺掺杂取代而LaCoO₃钙钛矿结构基本保持不变,适量Mg²⁺对Co³⁺的掺杂取代可形成晶格畸变和杂质能级、衍生Co⁴⁺及促进溶氧吸附从而有利于RhB的光催化降解,过量掺杂的Mg则可能成为光生载流子复合中心从而不利于RhB的去除。适量MgO异质结复合改性LaCoO₃一方面赋予复合催化剂较大表面积,利于RhB富集,也赋予丰富的表面羟基利于光生电子的捕获并衍生活性羟基自由基;另一方面还可能通过LaCoO₃与MgO异质结间电子的跃迁和流动以及晶格氧空位抑制光生载流子的复合,提高复合催化剂的光量子效率。     

NaF浸泡处理对BiOBr光催化降解有机染料罗丹明B的影响

以五水硝酸铋(Bi(NO_3)_3·5H_2O)和溴代十六烷基吡啶(CPB)为原料,通过水热法合成溴氧化铋(BiOBr)光催化剂,并在pH=3.3的条件下分别用0.01 mol/L、0.1 mol/L、0.3 mol/L NaF溶液对其进行浸泡氟化处理得新催化剂BiOBr-F_(0.01)、BiOBr-F_(0.1)和BiOBr-F_(0.3).运用XRD(X-射线衍射)、SEM(扫描电镜)、UV-Vis DRS(紫外-可见漫反射光谱)、XPS(X-射线光电子能谱)、FL(荧光光谱)等技术对催化剂的物理结构及性质进行表征并研究了其在可见光(λ≥420 nm)下对有机染料罗丹明B(Rhodamine B,RhB)的催化降解活性.结果表明,随着NaF浓度增加,催化剂的结构及性质均发生一定程度的改变.氟化使得BiOBr对RhB的矿化能力减弱;但BiOBr-F_(0.1)使RhB褪色加快.RhB在降解过程中涉及到超氧自由基(O_2~(·-))、羟基自由基(·OH)及空穴(h~+)氧化,矿化率减小归因于活性物种产量降低,BiOBr-F_(0.1)使褪色加速则是加快了RhB的脱烷基过程,使最大吸收峰快速蓝移.     

花状ZnO/ZnS异质结构的简易合成、结构表征及光催化活性

采用简便的两步溶液相化学方法,在较低温度下(80℃),制备出了花状的ZnO/ZnS异质结构。分别利用X射线衍射、X射线光电子能谱仪、扫描电子显微镜、透射电子显微镜、紫外-可见光谱仪等测试手段对所制备的样品进行表征,结果表明ZnO/ZnS异质结构是由花状ZnO纳米结构和ZnS纳米粒子组成。在光降解罗丹明B(RhB)的测试中,ZnO/ZnS异质结构样品体现出了比ZnO前驱物和商业P25光催化剂更高的光催化效率,这主要可归因于异质结构更有利于电子-空穴的有效分离。ZnO/ZnS光催化剂体现出良好的循环稳定性。     

增强光催化活性的3D分级结构Bi2W06微球及表面酸性

以KNO3为矿化剂,用水热法制备了3D分级结构Bi2WO6微球,通过XRD、SEM、BET对产物进行了表征．探讨了3D分级结构Bi2WO6微球可能的形成机理．以罗丹明B为模型污染物,研究了合成产物的光催化性质．结果表明：在紫外光下,RhB的降解以共轭结构断裂的光催化反应为主;而在可见光照射下,RhB的降解可能是光催化和光敏化共同作用的结果．进一步以吡啶为探针分子,通过吸附吡啶红外光谱探讨了Bi2W06表面酸性与光催化降解RhB之间的关系．研究显示,Bi2W06具有较强的表面酸性,增强了Bi2WO6与RhB分子之间吸附作用,有利于染料分子上的电子跃迁至催化剂上,易于发生光敏化和光催化反应。