基于还原氧化石墨烯-碳纳米管复合物的电化学传感器对木犀草素的检测

利用一步电化学原位还原法制备了还原氧化石墨烯/多壁碳纳米管复合物(ErGO/MWCNTs),研究木犀草素在该复合物修饰电极(ErGO-MWCNTs/GCE)上的电化学行为,构筑了一种简易、灵敏的电化学传感器用于木犀草素的检测。结果表明,相较于裸电极和ErGO/GCE,ErGO-MWCNTs/GCE利用两种材料的协同作用有效促进了对木犀草素的电催化性能,表现出更灵敏的电流响应。在优化条件下,峰电流与木犀草素的浓度在2.5×10~(-7)～1.3×10~(-5 )mol·L~(-1)范围内呈良好线性关系,检测限为70 nmol·L~(-1)。     

辣根过氧化物酶/多壁碳纳米管修饰铂电极生物传感器用于过氧化氢的循环伏安测定

将1mg多壁碳纳米管(MWCNT's)分散在5mL的0.5g·L~(-1)壳聚糖溶液中后,滴涂在铂电极表面,制得多壁碳纳米管修饰电极。将上述修饰电极在辣根过氧化物酶(HRP)溶液中浸泡8h,在MWCNT's修饰电极表面静电吸附辣根过氧化物酶,制成过氧化氢生物传感器,用于过氧化氢的测定。试验结果表明:在pH 6.0的磷酸盐缓冲溶液中,HRP/MWCNT's修饰电极对过氧化氢具有明显的电催化还原作用,过氧化氢的浓度在3.5×10~(-5)～9.0×10~(-3)mol·L~(-1)范围内与其还原峰电流呈线性关系,检出限(3S/N)为2.4×10~(-5)mol·L~(-1)。用标准加入法作回收试验,回收率在96.0%～101.8%之间。     

辣根过氧化物酶修饰电极在离子液体[EMIM]BF4中的直接电化学

将壳聚糖(Chi)-辣根过氧化物酶(HRP)-多壁碳纳米管(MWCNTs)的复合物修饰在玻碳电极(GCE)表面, 制备了HRP修饰电极(Chi-HRP-MWCNTs/GCE), 并将其用于在亲水性离子液体1-乙基-3-甲基咪唑四氟硼酸([EMIM]BF4)中HRP的直接电化学研究. 紫外可见光谱和红外光谱表明, HRP在复合物内保持了其原始构象. 电化学研究表明, 该修饰电极在[EMIM]BF4中的循环伏安图上出现了一对峰形良好、几乎对称的氧化还原峰, 式量电位为－0.247 V (vs. Ag/AgCl), 说明包埋在Chi-MWCNTs中的HRP与电极之间发生了直接电子传递; HRP在电极表面直接电子转移的速率常数ks为3.12 s－1; 在65 ℃的[EMIM]BF4中HRP仍然保持其活性; HRP修饰电极对过氧化氢的还原具有电催化作用, 其表观米氏常数Km为5.6×10－5 mol•L－1, 催化电流与过氧化氢浓度在5.0×10－7～5.0×10－5 mol•L－1范围内呈线性关系, 检出限为2.0×10－7 mol•L－1. 该研究为非水相生物传感器的构制提供了一种新途径.     

N-CTS/MWNTs/GCE电化学传感器对多巴胺和槲皮素的检测

通过N-酰化壳聚糖(N-CTS)与多壁碳纳米管(MWNTs)复合修饰玻碳电极得到N-CTS/MWNTs/GCE电化学传感器。采用循环伏安法研究了多巴胺(DA)和槲皮素(QU)在修饰电极上电化学行为。结果表明:NCTS/MWNTs/GCE电极能显著提高DA、QU的氧化峰电流,降低其氧化峰电位。在p H分别为7.38、6.80磷酸盐缓冲溶液中,DA、QU的氧化峰电流与浓度存在线性关系,线性方程分别为:Ip(DA)=0.0397+4715.8673 c、Ip(QU)=-0.2645+256.8935 c,相关系数均大于0.997,多巴胺、槲皮素检测限分别达1.0×10-8mol·L~(-1)和1.0×10-6mol·L~(-1)。N-CTS/MWNTs/GCE电极具有较好的重现性、稳定性,相对标准偏差为1.51%。该修饰电极可用于含DA、QU成分药物的直接测定。     

单层二硫化钨-羧基化多壁碳纳米管修饰玻碳电极测定水中对硝基苯胺

制备单层二硫化钨(WS_2)与羧基化多壁碳纳米管(CMWCNTs)复合材料,用以修饰玻碳电极(GCE),构建了 WS_2/CMWCNTs/GCE电化学传感器测定水中对硝基苯胺(PNA)。采用循环伏安法(CV)对修饰电极进行表征,探讨了 PNA在修饰电极上的电化学行为,结果表明:WS_2/CMWCNTs复合膜对PNA有显著的电催化作用,循环伏安曲线显示在pH 7.0的磷酸盐缓冲溶液中,PNA在-0.7 V处有明显的还原峰,在优化的试验条件下,PNA的浓度在500 μmol·L~(-1)以内与其峰电流呈线性关系,检出限(3s/k)为0.63 μmol·L~(-1)。应用构建的修饰电极对废水进行分析,加标回收率为92.8%～102%,测定值的相对标准偏差(n=6)均小于5.0%。     

纳米银-多壁碳纳米管修饰玻碳电极用于微分脉冲伏安法测定水中氯离子

用化学镀方法制备了纳米银覆盖多壁碳纳米管的复合材料,将其分散在水中配成1.0g·L~(-1)的悬浮液并滴涂在玻碳电极表面,制得纳米银-多壁碳纳米管修饰电极(nano Ag/MWCNT's/GCE)。用循环伏安法研究了在pH 6.0的磷酸盐支持电解质中,在—0.60～1.0V(vs.SCE)电位范围内,氯离子在nano Ag/MWCNT's/GCE上的电化学行为,结果表明:在氮气氛围中,修饰电极的氧化峰和还原峰分别位于0.19V和—0.20V电位处;随着氯离子浓度的增加,修饰电极的氧化峰电流降低,氯离子浓度在8.0×10~(-3)～0.1mol·L~(-1)之间与微分脉冲氧化峰电流的降低值呈线性关系。提出了用微分脉冲伏安法测定氯离子的方法,修饰电极用于自来水中氯离子的测定,回收率在98.5%～100.3%之间。     

DNA-Fe配合物生物聚合离子膜修饰玻碳电极的制备及其用作过氧化氢电化学传感器的研究

将1.00g·L~(-1) DNA溶液与1.00mmol·L~(-1)三氯化铁溶液混合制得DNA-Fe(Ⅲ)配合物溶液。取溶液20μL滴涂于经抛光的GCE表面,滴加0.50g·L~(-1) CTS溶液10μL,于20℃干燥22h制得DNA-Fe/CTS修饰的GCE电极。利用扫描电子显微镜对DNA-Fe/CTS BPICM的形貌进行了表征。采用循环伏安法和安培-时间曲线法研究该修饰电极的电化学特性及该电极对过氧化氢的电化学响应。结果表明,固定在聚合膜中的铁离子表现出较好的电化学活性,DNA-Fe/CTS/GCE对过氧化氢的还原反应具有较好的电催化活性。由此提出了一种新型生物相容性过氧化氢电化学传感器。该传感器的线性范围为0.01~2.0mmol·L~(-1),检出限(3S/N)为3μmol·L~(-1)。     

壳聚糖-超高纯单壁碳纳米管修饰电极检测Pb2+

基于壳聚糖(chitosan,CS)独特的吸附、螯合性能以及超高纯单壁碳纳米管(ultra-high purity single wall carbon nanotube,uhp-SWCNT)大的比表面积和高的电催化活性构建一种灵敏检测Pb~(2+)的电化学传感器。通过超声法制备壳聚糖-超高纯单壁碳纳米管纳米复合材料用于修饰玻碳电极。采用电化学阻抗(EIS)和微分脉冲溶出伏安法(DPSV)表征了CS/uhp-SWCNT纳米复合材料修饰玻碳电极的电化学行为。结果发现,CS和uhp-SWCNT具有良好的协同作用,能显著提电流响应。在优化的实验条件下,采用DPSV法检测Pb~(2+),溶出峰电流与其浓度在0.5～30μg·L~(-1)和30～60μg·L~(-1)范围内呈良好线性关系,检出限为0.1μg·L~(-1)(S/N=3)。构建的传感器成功用于检测水样中Pb~(2+),测定结果与石墨炉原子吸收光谱法几乎一致。     

基于固体酶催化反应电化学测定酶含量

提出了以固体辣根过氧化物酶(HRP)对过氧化氢氧化邻苯二胺的催化作用为基础的测定HRP及其标记物的电化学方法.测定中以Au-Pt/PAN/GCE为工作电极,并详细叙述其制备过程.将一定浓度的HRP按规定方法固定在上述修饰电极上制得HRP/Au-Pt/PAN/GCE修饰电极,将此电极浸入含5.0×10-3mol·L-1邻苯二胺及2.5×10-3mol·L-1过氧化氢的磷酸盐缓冲溶液(pH 5.0)中,反应10 min后将电极取出,记录溶液中酶催化反应产物的方波伏安峰及峰电流.结果表明:酶催化反应前,底物在工作电极上于-0.488 V(vs.SCE)处有明显的还原峰,在酶催化反应后,在-0.584 V处出现一个更大的还原峰,电位负移160 mV,且峰电流明显增大.峰电流值(Ip)与修饰在Au-Pt/PAN/GCE电极上的HRP的含量在1.0×10-2～2.0×102μg·L-1之间呈线性关系,方法的检出限(3S/N)为3.0 ng·L-1.     

聚苯胺纳米管/壳聚糖修饰玻碳电极循环伏安法测定阿米卡星

将1.0g·L~(-1)聚苯胺纳米管-N,N-二甲基甲酰胺(DMF)溶液和1.0g·L~(-1)壳聚糖乙酸溶液以1比50的比例混合,并超声处理1h后滴涂在玻碳电极表面,制得聚苯胺纳米管/壳聚糖修饰电极(记为PANT′s/CTS/GCE)。采用循环伏安法研究了阿米卡星在聚苯胺纳米管/壳聚糖修饰电极上的电化学行为。试验结果表明:在pH5.0磷酸盐缓冲溶液中,阿米卡星在聚苯胺纳米管/壳聚糖修饰电极于-0.2V处出现一个不可逆的还原峰,且还原峰电流与阿米卡星的质量浓度在10.0～80.0mg·L~(-1)范围内呈线性关系,检出限(3S/N)为8.0mg·L~(-1)。应用此法测定注射液中阿米卡星的含量,测定结果与分光光度法测定值相一致。     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

The preparation of NbH5(Me2PCH2CH2Me2)2 and NbHL2(Me2PCH2CH2PMe2)2 (L = CO or C2H4)

MMe₅(dmpe) (M = Nb or Ta, dmpe = Me₂PCH₂CH₂PMe₂) reacts with H₂ (500 atm) and dmpe in THF at 60°C to give MH₅(dmpe)_2? NbH₅(dmpe)₂ readily reacts with two mol of CO or ethylene (L) to give NbHL₂(dmpe)₂. The exchange of the hydride ligand with the ethylene protons in NbH(C₂H₄)₂(dmpe)₂ is not rapid on the ¹H NMR time scale (60 MHz) at 95°C.     

Formation of [Cp2TiSbMe2]2, [Cp2TiSb(SiMe3)2]2 and [Cp2TiCl]2·2Mes4Sb2

Reactions of [Cp₂Ti(btmsa)] (btmsa = bis(trimethylsilyl)acetylene) with R₄Sb₂ (R = Me, Me₃Si) give [Cp₂TiSbMe₂]₂ (1) or [Cp₂TiSb(SiMe₃)₂]₂ (2) respectively. [Cp₂TiCl]₂·2Mes₄Sb₂ (3) is serendipitously formed from [Cp₂Ti(btmsa)] and Mes₂SbH containing NH₄Cl traces.     

Conversion of NO in NO/N2, NO/O2/N2, NO/C2H4/N2 and NO/C2H4/O2/N2 Systems by Dielectric Barrier Discharge Plasmas

An experimental study on the conversion of NO in the NO/N₂, NO/O₂/N₂, NO/C₂H₄/N₂ and NO/C₂H₄/O₂/N₂ systems has been carried out using dielectric barrier discharge (DBD) plasmas at atmospheric pressure. In the NO/N₂ system, NO decomposition to N₂ and O₂ is the dominating reaction; NO conversion to NO₂ is less significant. O₂ produced from NO decomposition was detected by an on-line mass spectrometer. With the increase of NO initial concentration, the concentration of O₂ produced decreases at 298 K, but slightly increases at 523 K. In the NO/O₂/N₂ system, NO is mainly oxidized to NO₂, but NO conversion becomes very low at 523 K and over 1.6% of O₂. In the NO/C₂H₄/N₂ system, NO is reduced to N₂ with about the same NO conversion as that in the NO/N₂ system but without NO₂ formation. In the NO/C₂H₄/O₂/N₂ system, the oxidation of NO to NO₂ is dramatically promoted. At 523 K, with the increase of the energy density, NO conversion increases rapidly first, and then almost stabilizes at 93–91% of NO conversion with 61–55% of NO₂ selectivity in the energy density range of 317–550 J L⁻¹. It finally decreases gradually at high energy density. A negligible amount of N₂O is formed in the above four systems. Of the four systems studied, NO conversion and NO₂ selectivity of the NO/C₂H₄/O₂/N₂ system are the highest, and NO/O₂/C₂H₄/N₂ system has the lowest electrical energy consumption per NO molecule converted.     

KCl-KBO2-K2CO3, K2MoO4-KBO2-K2CO3, and K2WO4-KBO2-K2CO3 ternary systems

phase diagrams of KCl-KBO₂-K₂CO₃, K₂MoO₄-KBO₂-K₂CO₃, and K₂WO₄-KBO₂-K₂CO₃ ternary systems were studied by a calculation-experimental method and differential thermal analysis (DTA). The coordinates of ternary eutectics were determined to be E ₁: 622°C, 8.5 mol % KBO₂, 56.5 mol % KCl, and 35 mol % K₂CO₃; E ₂: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂MoO₄; E ₃: 710°C, 23 mol % KBO₂, 43 mol % K₂CO₃, and 34 mol % K₂WO₄. The specific heats of melting of the eutectics were determined.     

Cu-MOF催化过氧化氢应用于多巴胺的检测

本文利用一种具有H_2O_2催化活性的Cu-MOF[Cu_3(BTC)_2(H_2O)_3,简称HKUST-1],构建了以邻苯二胺(OPD)为颜色指示分子的比色传感体系,实现了对H_2O_2和多巴胺(DA)的快速灵敏检测。HKUST-1起到催化H_2O_2氧化OPD的作用,反应体系能够呈现出显著的颜色变化。在优化条件下,415nm处的吸收峰强度与H_2O_2浓度呈双线性关系,线性范围分别为10~50 mmol/L和50~100 mmol/L,相对标准偏差分别为0.9947和0.9995,最低检出限为1.29mmol/L。由于DA能抑制H_2O_2氧化OPD,因此比色传感体系还可以用于快速检测DA,线性范围分别为0.25~5μmol/L和2.5~25μmol/L,相对标准偏差分别为0.9783和0.9705,最低检出限为0.262μmol/L。该项工作拓展了Cu-MOFs材料在生物分子催化和生物传感方面的应用。     

Formation of nano-crystalline quartz crystals from ZnO/MgO/Al2O3/TiO2/ZrO2/SiO2 glasses

Glasses with the compositions 50.9 SiO₂ · 20.8 Al₂O₃ · (20.8 ? x) MgO· × ZnO · 3.7 TiO₂ · 3.7 ZrO₂ with x = 0, 2.3, 4.6 and 9.3 were annealed at temperatures in the range from 850 to 1100 °C. Depending on temperature, high- or low-quartz solid solutions, magnesium aluminosilicate, mullit and spinel precipitated. These glass–ceramics exhibit excellent mechanical properties and are potential candidates for applications in micromechanics or as hard disc substrate.The larger the ZnO concentration, the lower is the glass transition temperature. Also microhardnesses and Young’s moduli increased with increasing ZnO concentration. The nucleation temperature was of minor importance. To achieve good mechanical properties, the initially formed high-quartz phase must transform to the corresponding low-quartz phase. This occurs if the quartz phase contains only minor MgO or ZnO concentrations, which can be achieved by increasing the annealing times or temperature. Then MgO, ZnO and Al₂O₃ occur as separate spinel or gahnite phase.     

Synthesis and characterization of inorganic solid electrolytes of Li2O-SiO2-P2O5 and Li2O-TiO2-SiO2-P2O5 systems

The lithium-ion-conducting inorganic solid electrolytes in the oxide systems Li₂O-SiO₂-P₂O₅ and Li₂O-TiO₂-SiO₂-P₂O₅ were prepared by the solid-state reaction, and the electrolyte pellet made by cold-pressing method had diameter of 13 mm and was about 1 mm thick. Phase identification and surface morphology of the products were carried out by X-ray diffraction and scanning electron microscopy. Ionic conductivity of the pellets was investigated through ac impedance. The results show that the adding of other cations can improve the ionic conductivity of the solid electrolyte, and the sintering temperature and duration can influence the ionic conductivity. The maximum ionic conductivity in the samples is 9.9 × 10⁻⁴ S/cm in the Li₂O-TiO₂-SiO₂-P₂O₅ system. Original Russian Text ? W. Li, M. Wang, Z.H. Li, X.F. Shang, H. Wang, Y.W. Wang, Y.B. Xu, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 11, pp. 1341–1345.     

Reaction Mechanisms in Both a CCl2F2/O2/Ar and a CCl2F2/H2/Ar RF Plasma Environment

Decomposition of dichlorodifluoromethane (CCl₂F₂ or CFC-12) in aradiofrequency (RF) plasma system is demonstrated. The CCl₂F₂decomposition fractions _{CCl 2 F 2} and mole fractionsof detected products in the effluent gas stream of CCl₂F₂/O₂/Ar andCCl₂F₂/H₂/Ar plasma, respectively, have been determined. The experimentalparameters including input power wattage, O₂/CCl₂F₂ or H₂/CCl₂F₂ ratio,operational pressure, and CCl₂F₂ feeding concentration wereinvestigated. The main carbonaceous product in the CCl₂F₂/O₂/Arplasma system was CO₂, while that in the CCl₂F₂/H₂/Ar plasma systemwas CH₄ and C₂H₂. Furthermore, the possible reaction pathways werebuilt-up and elucidated in this study. The results of the experimentsshowed that the highly electronegative chlorine and fluorine wouldeasily separate from the CCl₂F₂ molecule and combine with the addedreaction gas. This led to the reactions terminated with the CO₂,CH₄, and C₂H₂ formation, because of their high bonding strength. Theaddition of hydrogen would form a preferential pathway for the HCland HF formations, which were thermodynamically stable diatomicspecies that would limit the production of CCl₃F, CClF₃, CF₄, andCCl₄. In addition, the HCl and HF could be removed by neutral orscrubber method. Hence, a hydrogen-based RF plasma system provideda better alternative to decompose CCl₂F₂.     

Removal of NO in NO/N2, NO/N2/O2, NO/CH4/N2, and NO/CH4/O2/N2 systems by flowing microwave discharges

In this paper, continuing previous work, we report on experiments carried out to investigate the removal of NO from simulated flue gas in nonthermal plasmas. The plasma-induced decomposition of small concentrations of NO in N2 used as the carrier gas and O2 and CH4 as minority components has been studied in a surface wave discharge induced with a surfatron launcher. The reaction products and efficiency have been monitored by mass spectrometry as a function of the composition of the mixture. NO is effectively decomposed into N2 and O2 even in the presence of O2, provided always that enough CH4 is also present in the mixture. Other majority products of the plasma reactions under these conditions are NH3, CO, and H2. In the absence of O2, decomposition of NO also occurs, although in that case HCN accompanies the other reaction products as a majority component. The plasma for the different reaction mixtures has been characterized by optical emission spectroscopy. Intermediate excited species of NO*, C*, CN*, NH*, and CH* have been monitored depending on the gas mixture. The type of species detected and their evolution with the gas composition are in agreement with the reaction products detected in each case. The observations by mass spectrometry and optical emission spectroscopy are in agreement with the kinetic reaction models available in literature for simple plasma reactions in simple reaction mixtures.