Plasma etching treatment for surface modification of boron-doped diamond electrodes

Boron-doped diamond (BDD) thin film surfaces were modified by brief plasma treatment using various source gases such as Cl₂, CF₄, Ar and CH₄, and the electrochemical properties of the surfaces were subsequently investigated. From X-ray photoelectron spectroscopy analysis, Cl and F atoms were detected on the BDD surfaces after 3 min of Cl₂ and CF₄ plasma treatments, respectively. From the results of cyclic voltammetry and electrochemical AC impedance measurements, the electron-transfer rate for Fe(CN)₆^3−/4− and Fe^2+/3+ at the BDD electrodes was found to decrease after Cl₂ and CF₄ plasma treatments. However, the electron-transfer rate for Ru(NH₃)₆^2+/3+ showed almost no change after these treatments. This may have been related to the specific interactions of surface halogen (C-Cl and C-F) moieties with the redox species because no electrical passivation was observed after the treatments. In addition, Raman spectroscopy showed that CH₄ plasma treatment of diamond surfaces formed an insulating diamond-like carbon thin layer on the surfaces. Thus, by an appropriate choice of plasma source, short-duration plasma treatments can be an effective way to functionalize diamond surfaces in various ways while maintaining a wide potential window and a low background current.     

火焰原子吸收分光光度法测定焊锡中的镉

研究了火焰原子吸收分光光度法测定焊锡中镉的方法。试样用盐酸-硝酸混合酸消解处理,在盐酸介质中测定。镉测定范围在0.00005%~0.005%之间,加标回收率为98.5%~102.6%,RSD为0.664%~5.35%。     

火焰原子吸收光谱法测定牛奶中铁和锌

先将牛奶碳化，再用酸溶解，利用TritonX-100使测定铁、锌的灵敏度分别提高8．3％、16．4％，且有效地消除了牛奶中存在的其他金属离子的干扰。该方法简单、快速、准确。     

火焰原子吸收光谱法测定人发中的微量元素

首先用H2 SO4 将头发炭化 ,再用H2 SO4 、HClO4 及H2 O2 溶解碳化物 ,利用火焰原子吸收光谱法 ,可以安全、准确、迅速地测定出人发中钙、铁、锌、铜的含量     

Atmospheric Pressure Plasma Processing for Polymer Adhesion: A Review

Atmospheric pressure plasma processing has attracted significant interests over decades due to its usefulness and a variety of applications. Adhesion improvement of polymer surfaces is among the most important applications of atmospheric pressure plasma treatment. Reflecting recent significant development of the atmospheric pressure plasma processing, this work presents its fundamental aspects, applications, and characterization techniques relevant to adhesion.     

等离子体聚合物薄膜的性质及应用进展

概述了利用低温等离子体技术制备的有机聚合物薄膜特性、主要合成方法及研究现状，简要讨论了等离子体聚合条件对薄膜结构和性质的影响；介绍了现代分析技术对聚合物薄膜结构的表征；阐述了近年来对低温等离子体聚合物薄膜的物理性质(包括表面性质、渗透性、电学和光学性质等)的研究新进展，并描述了其在工业生产上的一些应用。     

低温等离子体在高分子材料表面改性中的应用

概述了低温等离子体对高分子材料表面改性的主要方法及其低温等离子体技术在提高高分子材料表面亲疏水性、粘结性、导电性和生物相容性等性能方面的应用,特别是对低温等离子体在生物医用高分子材料领域的应用进行了分析和展望。     

Horseradish peroxidase immobilized in TiO2 nanoparticle films on pyrolytic graphite electrodes: direct electrochemistry and bioelectrocatalysis

Horseradish peroxidase (HRP)-TiO₂ film electrodes were fabricated by casting the mixture of HRP solution and aqueous titania nanoparticle dispersion onto pyrolytic graphite (PG) electrodes and letting the solvent evaporate. The HRP incorporated in TiO₂ films exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks at about −0.35 V versus saturated calomel electrode (SCE) in pH 7.0 buffers, characteristic of HRP-Fe(III)/Fe(II) redox couple. The electron exchange between the enzyme and PG electrodes was greatly enhanced in the TiO₂ nanoparticle film microenvironment. The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (k_s) and formal potential (E°′) were estimated by fitting the data of square wave voltammetry with nonlinear regression analysis. The HRP-TiO₂ film electrodes were quite stable and amenable to long-time voltammetric experiments. The UV-Vis spectroscopy showed that the position and shape of Soret absorption band of HRP in TiO₂ films kept nearly unchanged and were different from those of hemin or hemin-TiO₂ films, suggesting that HRP retains its native-like tertiary structure in TiO₂ films. The electrocatalytic activity of HRP embedded in TiO₂ films toward O₂ and H₂O₂ was studied. Possible mechanism of catalytic reduction of H₂O₂ with HRP-TiO₂ films was discussed. The HRP-TiO₂ films may have a potential perspective in fabricating the third-generation biosensors based on direct electrochemistry of enzymes.     

光学玻璃用高纯度硝酸钾中微量钠的火焰原子吸收光谱法测试

介绍了火焰原子吸收法测试智能手机触摸屏用高纯度硝酸钾中微量钠的方法,优化了仪器的灯电流、狭缝宽度、乙炔与空气流量,研究了标准曲线选择、最大称样量及消电离剂用量等条件。该方法用于智能手机触摸屏用高纯度硝酸钾中微量钠的测试,检出限为0.002%,相对标准偏差为2.88%,回收率在95.00%~101.25%。     

低温等离子体技术在超高相对分子质量聚乙烯纤维表面改性中的应用

介绍了低温等离子体的概念、分类及其在超高相对分子质量聚乙烯纤维(UHMWP E)表面改性方面的特点;阐述了国内外在低温等离子体对UHMWPE纤维表面改性前后纤维本身及其复合材料性能的影响情况;简介了用自行研制的低温等离子体设备对UHMWPE纤维进行表面改性的研究结果和低温等离子体处理UHMWPE纤维表面改性的发展前景。实验表明,UHMWPE纤维经过等离子体处理后表面产生刻蚀和交联,其与树脂间的粘结性能改善;该低温等离子体设备能满足UHMWPE纤维表面改性连续化生产需要。     

Physicochemical and Adhesion Characteristics of High-Density Polyethylene when Treated in a Low-Pressure Plasma under Different Electrodes

The present investigation studys the effects of different electrodes such as copper, nickel, and stainless steel under low-pressure plasma on physicochemical and adhesion characteristics of high-density polyethylene (HDPE). To estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to low-pressure plasmas have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that the surface energy and its polar component increase with increasing exposure time, attain a maximum, and then decrease. The increase in surface energy and its polar component is relatively more important when the polymer is exposed under a stainless-steel electrode followed by a nickel and then a copper electrode. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by optical microscopy and electron spectroscopy for chemical analysis (ESCA). It is observed that when the HDPE is exposed under these electrodes, single crystals of shish kebab structure form, and the extent of formation of crystals is higher under a stainless-steel electrode followed by nickel and then copper electrodes. Exposure of the polymer under low-pressure plasma has essentially incorporated oxygen functionalities on the polymer surface as detected by ESCA. Furthermore the ESCA studies strongly emphasize that higher incorporation of oxygen functionalities are obtained when the polymer is exposed to low-pressure plasma under a stainless-steel electrode followed by nickel and then copper electrodes. These oxygen functionalities have been transformed into various polar functional groups, which have been attributed to increases in the polar component of surface energy as well as the total surface energy of the polymer. Therefore, the maximum increase in surface energy results in stronger adhesion of the polymer when the polymer is exposed under a stainless-steel electrode rather than nickel and copper electrodes.     

Immobilization of horseradish peroxidase on self-assembled (3-mercaptopropyl)trimethoxysilane film: Characterization, direct electrochemistry, redox thermodynamics and biosensing

Highly organized (3-mercaptopropyl)trimethoxysilane (3-MPT) films have been prepared via self-assembled coupled with sol–gel linking technology. Horseradish peroxidase (HRP) is successfully immobilized onto the densely packed three-dimensional (3D) 3-MPT network and the direct electrochemistry of HRP is achieved without any electron mediators or promoters. Redox thermodynamics of HRP on the 3-MPT films, which is obtained from the temperature dependence of the reduction potential, suggests that the positive shift of redox potentials of HRP at the interface of 3-MPT originates from the solvent reorganization effects and conformational change of the polypeptide chain of HRP. Based on the direct electrochemistry and electrocatalytic ability of HRP, a sensitive third-generation amperometric H₂O₂ biosensor is developed with two linear dependence ranges of 5.0 × 10⁻⁷ to 1.0 × 10⁻⁴ and 1.0 × 10⁻⁴ to 2.0 × 10⁻² mol L⁻¹.     

Solvent nature effect in preparation of perovskites by flame pyrolysis: 2. Alcohols and alcohols + propionic acid mixtures

The effect of either pure alcohols or alcohols + propionic acid mixtures as solvents for the preparation by flame pyrolysis of a standard LaCoO₃ catalyst, to be employed for the catalytic flameless combustion of methane, has been investigated. All the catalysts proved very active for the mentioned reaction. Low-MW pure alcohols showed however less suitable than alcohols-propionic acid mixtures, leading to lower perovskite phase purity, less particle size homogeneity and lower specific surface area. The high volatility of the solvent seems to be the major cause, together with the improper behaviour of nitrates (forced by solubility reasons) as perovskite metals precursors. However, the addition of propionic acid to the alcohols allowed to use the acetates as precursors and hence to obtain high perovskitic phase purity, high SSA and uniform particle size. Moreover, the increase of combustion enthalpy of the solvent, through the addition of higher-MW alcohols, leading to progressively higher flame temperature, strongly improved the thermal resistance of the catalyst, without lowering catalytic performance.     

Second Harmonic Generation studies of the oxidation of metal electrodes: Compact and hydrous oxide growth at gold electrodes in acid solutions

The oxidation of gold electrodes in aqueous media has been examined using Second Harmonic Generation (SHG). Initial growth of the compact or α oxide causes a substantial drop in SH generation even when only partial coverage of oxide is attained and this is suggested to be due to the effect of the development of the oxide on a surface plasmon derived from d-electrons in gold, the involvement of these electrons in oxide formation meaning that the surface plasmon can no longer propagate. When thicker hydrous (or β) oxides are grown on top of the α oxide by holding at constant potential, the subsequent reduction of the oxide leads to unusual narrow peaks (dips) in the SHG response which occur before any significant reduction charge is passed. As the amount of hydrous oxide increases, the initial single narrow SHG peak changes to a pair of peaks and these then merge into one broad peak. The SHG peaks are suggested to be related to an order-disorder transition at the interface between α and β oxides, or perhaps due to the presence of surface traps. Second Harmonic Generation is shown again to be a sensitive and informative technique Having sub-monolayer sensitivity for α oxide growth and offering insight into the reduction process of multilayer oxides.     

Electrochemical oxidation of borohydride on platinum electrodes: The influence of thiourea in direct fuel cells

The electrochemical behaviour of sodium borohydride on a platinum electrode in the absence and presence of thiourea (TU) was investigated by cyclic voltammetry. In the absence of thiourea, several overlapping peaks associated with the hydrolysis of BH₄⁻ appear in the domain of hydrogen oxidation, i.e., in the potential range of −1.25 to −0.50 V versus Ag/AgCl. As a consequence of secondary reactions, the borohydride oxidation in 3 M NaOH solution shows a four to six-electron process, according to its concentration, in direct fuel cells. A conveyable TU/NaBH₄ concentration ratio of 0.6 inhibits the delivery of hydrogen simultaneously with catalytic hydrolysis of BH₄⁻. Thus, the coulombic efficiency in direct fuel cell discharge was increased showing an about eight-electron process for the oxidation of BH₄⁻.     

Effect of Ce dopant on upconversion and temperature sensing performances in homogeneous ultrasmall Y2O3:Yb3+/Ho3+ nanoparticles through flame aerosol synthesis

Flame aerosol synthesis (FAS) is an excellent strategy for continuous, fast, and mass production of small-size upconversion nanoparticles (UCNPs), which have high potential applications in fields like biological imaging, colour display and optical temperature sensing. However, flame-made UCNPs have received less attention, and relevant studies are limited. Herein, for the first time, we successfully fabricated cerium (Ce)-doped homogeneous ultrasmall Y₂O₃:Yb³⁺/Ho³⁺ UCNPs using a liquid-fed FAS method. Ce was doped to improve the upconversion luminescence (UCL) of the Y₂O₃:Yb³⁺/Ho³⁺ UCNPs. The overall UCL intensity was enhanced ～77.9-fold for an optimal concentration of 20 mol% Ce-doped UCNPs, compared with the UCNPs without Ce doping with a relatively homogeneous ultrasmall size of 8–10 nm. Further studies confirmed that both trivalent (Ce³⁺) and tetravalent (Ce⁴⁺) simultaneously exist in the Y₂O₃ hosts and are critical in enhancing the UCL properties. In addition, the fluorescence intensity ratio (FIR) method was used to evaluate the thermal properties of the fabricated UCNPs. Ce doping significantly improved the thermal sensitivity of Y₂O₃:Yb³⁺/Ho³⁺ UCNPs. An excellent relative sensitivity (S_R) of 0.622% K^?1 at 598 K was obtained for flame-made UCNPs doped with 20 mol% Ce.     

Electrochemical behaviour of high nitrogen bearing stainless steel in acidic chloride solution: Effects of oxygen, acid concentration and surface roughness

The effects of oxygen, H₂SO₄ concentration and surface roughness on the electrochemical behaviour of high nitrogen bearing stainless steel (HNS) in acidified 0.5 M NaCl solution were investigated using potentiodynamic polarization method. The results revealed three corrosion potentials indicating an unstable system. The number of the potentials was influenced by H₂SO₄ concentration. Three potentials existed above 0.011 M H₂SO₄, two between 0.011 and 0.0065 M H₂SO₄ and one below 0.0065 M H₂SO₄. Oxygen increased the number of corrosion potential at 0.005 M H₂SO₄ + 0.5 M NaCl solution while surface roughness had no noticeable influence on the number of potentials but increased the values of the corrosion potentials and passivation current densities with increase in the surface roughness. The corrosion mechanism has been discussed using the ideal polarization curve models.     

Electrochemical sensors for detection of hydrogen in air: model of the non-Nernstian potentiometric response of platinum gas diffusion electrodes

The potentiometric response of three different platinum gas diffusion electrodes deposited on H₃PO₄ doped polybenzimidazole (PBI) was investigated under humidified atmospheres that contained H₂ or mixtures of H₂ and O₂. Continuum modelling was used to analyse the response. It is shown that the non-Nernstian response under H₂H₂ON₂ mixtures can be explained by a difference of water activity on both sides of the membrane. Under H₂O₂N₂ mixtures, the oxygen mass transport parameters have a strong effect on the electrode sensitivity.     

放电等离子烧结技术在陶瓷材料制备中的应用

放电等离子烧结(SPS)作为一种先进的材料制备技术,与传统烧结方法相比,在材料制备效率及所制备的材料的性能方面都有明显的提高,因而引起了世界范围的关注与深入研究。基于相关文献报道,本文针对SPS技术在陶瓷材料中应用中的若干基础问题进行了评述,分别就陶瓷SPS过程中的等离子放电现象、温度与温度场分布、电流电场的促进作用、升温制度选择与设置、压力的作用与使用、模具的设计与开发等控制参数对材料烧结行为、微观结构与宏观性能的影响进行了讨论,并简要介绍了纳米陶瓷SPS过程中微观结构自发均匀化现象。