电化学法直接制备石墨烯/纳米金复合膜修饰电极及用于水中Cr(Ⅵ)检测

采用电还原氧化石墨烯(ERGO)和电沉积纳米金(AuNPs)粒子的方法修饰玻碳电极(GCE),直接制得ERGO/AuNPs/GCE复合膜修饰电极。探究了Cr(Ⅵ)在此修饰电极上的电化学行为。用扫描电子显微镜(SEM)、循环伏安法(CV)、电化学交流阻抗法(EIS)对修饰电极进行了表征。结果表明:ERGO/AuNPs/GCE复合膜修饰电极具有较大的电活性表面积和良好的电子传递能力。在最优条件下,即金的沉积电位及沉积时间分别为-0.4V和120s,1mg/mL的氧化石墨烯的滴涂量为3μL,制得的ERGO/AuNPs/GCE复合膜修饰电极,能实现对水体中Cr(Ⅵ)的高效、快速检测,检测限为0.3μmol/L,线性范围为1~100μmol/L。     

电沉积制备铁氰化镍/Nafion纳米粒子及其对葡萄糖的电化学检测

采用电沉积的方法,在玻碳电极表面快速电沉积均匀分布的铁氰化镍/Naion纳米粒子。用X射线能量色散光谱图(EDX)和扫描电镜(SEM)对样品进行了表征,然后采用循环伏安法对该修饰电极进行电化学研究。结果表明:该电极对葡萄糖具有良好的电催化氧化性能,对葡萄糖响应的线性范围为1.560×10~(-6)~10.32×10~(-3)mol/L(R~2=0.999),检出限为1.2μmol/L(S/N=3)。制得的修饰电极对葡萄糖的电催化具有灵敏度高、重现性好和选择性强的优点。     

电化学法制备铁氰化铜/Nafion及其对卡托普利的检测

为对药片中卡托普利的含量进行精确测定,采用电聚合的方法,在玻碳电极表面沉积均匀分布的铁氰化铜/Nafion复合物。用扫描电镜(SEM)和X射线能量色散光谱(EDX)分别对样品的形貌和成分进行表征。利用循环伏安法(CV)研究药物分子卡托普利在该修饰电极上的电化学行为。研究结果显示,该修饰电极对卡托普利具有非常好的电催化性能。一定条件下,卡托普利在6.62×10-5~3.80×10-3mol/L范围内,其氧化峰电流与物质量浓度呈现很好的线性关系,其相关系数是0.996,检出限为5.0×10-6mol/L。该修饰电极具有快速、灵敏和高效的特点,并且可用于卡托普利实际样品的检测。     

亚硫酸根在纳米铂-金/多壁碳纳米管修饰电极上的电化学行为及其测定

采用滴涂法和电化学共沉积法制备了纳米Pt-Au和多壁碳纳米管(MWCNTs)修饰玻碳电极(纳米Pt-Au/MWCNTs/GCE),采用循环伏安法(CV)研究了亚硫酸根在纳米Pt-Au/MWCNTs/GCE上的电化学行为。结果表明:在磷酸盐缓冲溶液(PBS)中,亚硫酸根在纳米Pt-Au/MWCNTs/GCE上产生了较明显的氧化峰。亚硫酸根的氧化峰电流与亚硫酸根的浓度在1.0×10~(-6)~2.0×10~(-3) mol/L的范围内呈现良好的线性关系(r=0.9936),检出限为1.0×10~(-7) mol/L(S/N=3)。该检测方法灵敏、简便、线性范围宽,可以用于实际样品中亚硫酸根的测定。     

纳米TiO2/还原石墨烯复合修饰电极用于食品中 柠檬黄的检测

为了检测食品中柠檬黄的含量,利用滴涂法和电化学还原法制备纳米TiO_2/还原石墨烯复合修饰玻碳电极(TiO_2-Er GO/GCE)。采用透射电子显微镜和X射线粉末衍射仪对TiO_2和TiO_2-GO两种修饰电极材料进行表征;通过循环伏安法观察了柠檬黄在不同电极上的电化学行为,并对检测条件如p H值、富集电位、富集时间进行了优化。实验结果表明:TiO_2-Er GO/GCE增大了电极的电化学活性面积,提高了柠檬黄的电化学氧化响应;最优的检测条件为p H值为3.7、富集电位为-0.20 V、富集时间为180 s;在最优的检测条件下,采用线性扫描伏安法检测柠檬黄的线性范围为2.0×10-8~2.0×10-5 mol/L,检测限为8.0×10-9 mol/L(信噪比为3)。     

基于[C_(10)-mim~+]Br~-固定HRP于Au/石墨烯复合材料电极表面的新型H_2O_2酶生物传感器

利用长链离子液体特殊的性质,用其固定HRP于Au/graphene电极表面(Nafion/HRP/[C10-mim+]Br-/Au/Gr/GCE)组装成H2O2传感器。用透射电镜来表征Au/氧化石墨烯的形貌,金纳米颗粒很均匀的分散在石墨烯表面,并不存在团聚现像。电化学技术检测Nafion/HRP/[C10-mim+]Br-/Au/Gr修饰电极对H2O2的响应情况,显示修饰电极对H2O2有很好的响应,在H2O2浓度2.0×10-6~1.2×10-3 mol/L的范围内,还原电流与浓度存在线性关系(R=0.997),检测限为3.0×10-7 mol/L;另外传感器具有很好的稳定性和选择性,为生物分子的检测提供新方法。     

掺氮石墨烯的溶剂热制备及对抗坏血酸氧化的电催化性能

以Hummers方法制备的氧化石墨烯为前驱体,在乙二胺和水的混合溶剂热条件下(150℃,8h)合成了掺氮石墨烯(NG)。通过XRD、FT-IR、XPS和电化学阻抗谱研究了掺氮石墨烯的结构和电化学性能。结果表明,通过溶剂热反应在石墨烯表面引入C—N,N—H等含氮基团。乙二胺不仅能对氧化石墨烯进行部分还原,而且还能对其进行掺氮功能修饰。电化学阻抗谱研究表明,掺氮石墨烯(NG)的电子转移阻抗明显小于相同条件下水热还原制备的石墨烯,说明功能修饰石墨烯大大改善了电子转移速率。将掺氮石墨烯修饰电极应用于对抗坏血酸的电化学检测,检出限达1.0×10-5~2.8×10-2 mol/L,最低检测限(3σ/slope)为1.7×10-7 mol/L。     

Pt-Fe(Ⅲ)/多壁碳纳米管修饰电极测定亚硫酸根

为建立一种简便、快速的亚硫酸根分析方法,采用滴涂法和电化学沉积法制备Pt-Fe(Ⅲ)/多壁碳纳米管(MWCNTs)修饰玻碳电极(Pt-Fe(Ⅲ)/MWCNTs/GCE),通过循环伏安法研究亚硫酸根在该修饰电极上的电化学行为,并优化实验条件,在此基础上建立一种伏安法测定亚硫酸根的新方法。亚硫酸根的氧化峰电流与其物质量浓度在8.0×10-6~7.0×10-3mol/L范围内呈良好的线性关系(r=0.998 9),检测限为3.0×10-6 mol/L,水样中亚硫酸根的加标回收率在98%~102%之间。该方法具有操作简便、分析速度快和线性范围宽的优点,可用于实际样品中亚硫酸根的测定。     

铁氰化物掺杂聚苯胺复合材料的制备和表征

以ITO导电玻璃为工作电极,在三电极系统中,采用循环伏安法制得聚苯胺薄膜,聚苯胺/铁氰化铜(CuHCF),聚苯胺/铁氰化钴(CoHCF),聚苯胺/铁氰化铈(CeHCF)复合材料。通过利用C-V、SEM、EDS、XRD、FT-IR等方法对导电复合物进行表征和性能研究。实验结果表明,制备复合物的最佳电解液浓度为0.02mol/L苯胺+0.002mol/L金属离子+0.01mol/L铁氰化钾+0.5mol/L H2SO4;聚苯胺与铁氰化物很好地键合在一起,聚苯胺/铁氰化钴复合材料的电化学性有进一步的提高,具有纳米粒子特性和独特的片状粒子结构;而聚苯胺/铁氰化铜和聚苯胺/铁氰化铈的电化学性能高于聚苯胺本体,粒子间有较大的空穴现象。     

基于石墨烯/金纳米棒的甲硝唑电化学行为及其检测

碱性条件下制备水中分散性良好的石墨烯,并通过一步还原法得到石墨烯/AuNRs复合材料。利用滴涂法制备石墨烯/AuNRs修饰电极,并研究了甲硝唑在该修饰电极上的电化学行为。结果表明,在pH=7.4时,甲硝唑在修饰电极上出现明显的氧化还原峰。甲硝唑在该修饰电极的还原峰峰电流与浓度在3.0×10-7～5.0×10-5 mol/L(S/N=3)范围内呈良好的线性关系,检出限为9.2×10-8 mol/L。该检测方法具有良好的灵敏度、选择性和稳定性,可用于甲硝唑药物的分析。同时也展现了这种新型的复合纳米材料在药物的检测中的应用潜力。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。