氧离子注入纳米金刚石薄膜的微结构和电化学性能研究

在纳米金刚石薄膜中注入剂量为1012cm-2的氧离子,并进行700,800,900和1000?C的真空退火处理,系统研究薄膜的微结构和电化学性能结果表明,氧离子注入未退火(O120)和氧离子注入1000?C退火(O121000)电极的电势窗口分别为4.60 V和3.61 V,远大于其他电极的电势窗口,并且这两个样品的电极传质效率较高,说明氧离子注入和高温退火有利于提高电极的传质效率.红外光谱测试表明,样品O120和O121000的表面没有碳氢基团终止层,而其他样品均含有氢终止层,说明氧离子注入和高温退火破坏了薄膜表面含碳氢基团的氢终止层,提高了薄膜的电化学性能Raman光谱测试结果表明,金刚石含量较高、内应力较小和非晶石墨相无序化程度较大的样品具有较好的电化学性能;并且薄膜晶界处的非晶碳的团簇数量或者尺寸减小,样品的电化学性能提高.     

Synthesis,crystal structure and electrocatalytic behavior of a copper (II) complex derived from acylpyrazolone double Schiff bases

A new double Schiff base complex, Cu(PMαFP)₂en (HPMαFP = 1‐phenyl‐3‐methyl‐4‐(2‐furoyl)‐5‐pyrazolone, en = ethylenediamine), has been synthesized and characterized by elemental analysis, IR, UV, fluorescence spectra, thermal analysis, X‐ray single crystal diffraction and cyclic voltammetry (CV). Its crystal structure is monoclinic with space group Pbca and cell parameters: a = 22.263(3)Å, b = 13.671(2)Å, c = 10.0920(16)Å, Z = 4, S = 1.028, R₁ = 0.0500 and wR₂ = 0.1285. It was found that the Cu²⁺ ion is located in the coordination center. The Cu(II) has a slightly distorted plane quadrilateral coordination environment with two oxygen atoms and two nitrogen atoms of double Schiff base ligand in the equatorial plane. The complex has a one‐dimensional chain supramolecular structure, which is connected by C H…N bonding interactions. In the electrochemical experiments, the CV curve displays an oxidation peak in the presence of uric acid with Ep = 0.216V in pH = 7.0, showing that the Cu(PMαFP)₂en/glassy carbon modified electrode has an electrocatalytic activity toward uric acid.     

熔盐法制备三元层状MAX相陶瓷的研究进展

MAX相是一种兼具金属和陶瓷性能的新型三元层状过渡金属碳氮化物。传统合成MAX相的方法都有一定的局限性,如反应温度较高、合成时间过长、合成样品较少,且大部分无法直接一步制备所需MAX相。近些年来,采用熔盐法合成MAX相的报道越来越多,并且工艺持续改进。本文从传统熔盐法合成MAX相出发,分析并阐述了新熔盐法合成MAX相的研究进展。传统熔盐法利用较低熔点的熔盐作为反应溶剂,提高了反应效率;熔盐屏蔽法以熔盐作为反应溶剂的同时还可防止氧化,使得反应可以在空气中进行;路易斯酸盐法则是将熔盐作为反应原料来合成MAX新相;熔盐电化学法以电脱氧的方式,将合成原料由纯金属改为金属氧化物,降低了生产成本。熔盐法所合成MAX相产物较传统方法所合成产物的产量及纯度更高,所需要的温度、能耗以及成本更低。因此,熔盐合成法是未来大批量合成MAX相以及MAX新相合成的一个重要方法。     

退火温度对CdSe纳米薄膜的形成及光电性能影响

在室温下,采用循环伏安法在ITO上沉积CdSe纳米薄膜。利用X射线衍射仪(XRD)、场发射扫描电镜(FESEM)、原子力显微镜(AFM)、X射线光电子能谱分析(XPS)、紫外-可见(UV-VIS)分光光度计以及电化学工作站对不同温度退火后的CdSe纳米薄膜的晶体结构、形貌、光学性能、光电化学性能进行表征和测试。结果表明,退火温度对CdSe纳米薄膜的形貌和性能起到关键性作用。薄膜表面平整、厚度均匀,且由呈纳米颗粒状的立方相CdSe构成;经退火后,CdSe纳米颗粒出现不同程度的长大现象,Se含量随退火温度的升高而减少。紫外-可见吸收光谱表明随着退火温度的升高,CdSe纳米薄膜对可见光的吸收发生红移,表明禁带宽度逐渐减小,表现出量子尺寸效应。通过光电流测试表明随着退火温度的升高,CdSe薄膜的光电响应效应显著提高。     

No more conventional reference electrode: Transition time for determining chloride ion concentration

Ion selective electrodes (ISE) are used extensively for the potentiometric determination of ion concentrations in electrolytes. However, the inherent drift in these measurements and the requirement of a stable reference electrode restrict the feasibility of this method for long-term in-situ applications. This work presents a chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode for measuring chloride ion concentration. An anodic current pulse is applied to a Ag/AgCl working electrode which initiates a faradaic reaction that depletes the chloride ions near the electrode surface. The rate of change in potential at the Ag/AgCl electrode, due to chloride ion depletion, reaches an inflection point once the chloride ions deplete completely near the electrode surface. The moment of the inflection point, also known as the transition time, is a function of the chloride ion concentration and is described by the Sand equation. It is shown that the square root of the transition time is linearly proportional to the chloride ion concentration. Drift in the response over two weeks is negligible: 59 μM/day when measuring 1 mM of Cl⁻ ions using a 10 A m⁻² current pulse. The transition time at a specific ion concentration can be tuned by the applied current pulse, e.g., in a solution containing 5 mM chloride ions, the transition times with current pulses of 10 and 20 A m⁻² are 1.56 and 0.25 s, respectively. The moment of inflection determines the response, and thus is independent of the absolute potential of reference electrode. Therefore, any metal wire can act as a pseudo-reference electrode, enabling this approach for long-term and integrated-sensor applications such as measurement inside concrete structures.     

两种方法制备的磷酸铁锂/石墨烯复合材料的性能对比

以FeSO₄·7H₂O、NH₄H₂PO₄、H₂O₂、Li₂CO₃、C₆H₁₂O₆和自制的氧化石墨烯(GO)为原料, 分别采用原位包覆法和非原位包覆法制备了石墨烯磷酸铁锂样品: LiFePO₄/C/G-1和LiFePO₄/C/G-2。用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、交流阻抗(EIS)和充放电测试研究了两种包覆方法制备的样品的晶体结构、形貌和电化学性能。结果表明原位法包覆所得复合材料LiFePO₄/C/G-1具有更优秀的电性能: 在2.5~4.1 V充放电, 0.1C和1C首次放电比容量分别为158.15和150.5 mAh·g^-1, 在1C倍率下循环500次后容量保持率达到98.3%。     

Trace Analysis by ESCA-Electrochemical Measurements

Abstract

A procedure which combines electrochemical deposition and ESCA measurements for the determination of trace levels of metals in solution is described. The method is demonstrated by an experiment in which microgram quantities of Pb, Cd, and Bi are deposited on a mercury-coated platinum electrode and then detected by ESCA measurements.     

Application of Electrochemical Detection for the Quantitation of 1, 4-Dihydroxy-5, 8-Bis-[2-(2-Hydroxyethyl) Aminoethylamino]-9,10-Anthracenedione Following Liquid Chromatography

Abstract

Electrochemical monitoring of 1, 4-dihydroxy-5, 8-bis-[2-(2-hydroxyethy1) aminoethy amino]-9, 10-anthracenedione was employed for the quantitation of this cancer chemotherapy drug following high performance liquid chromatography. Detection was performed by oxidation of the compound at a glassy carbon electrode at +0.80 V vs. SCE. A rapid and convenient sample treatment procedure was developed which is suitable for determination involving physiological samples. A detection limit of 2 ng injected was obtained for urine samples.     

Direct Electrochemical Determination of Hydroxymethylfurfural (HMF) and its Application to Honey Samples

Abstract

In this work an electrochemical method is evaluated for direct hydroxymethylfurfural (HMF) content determination in untreated honey samples. The HMF presented a single, well‐defined reduction signal at ?1100 mV vs. Ag/AgCl. Borate was confirmed as being the most suitable supporting electrolyte for determining HMF content in honey because it allowed better definition and selectivity of the HMF reduction signal. The detection limit for the differential pulse polarography method was 48 ppb and it was successfully applied to three samples of Mexican honey, using the standard addition method.