槲皮素在分子印迹聚合物修饰碳糊电极上的电化学行为及测定

建立分子印迹聚合物修饰碳糊电极测定药物中槲皮素含量的新方法。以槲皮素为模板分子,甲基丙烯酸为功能单体,偶氮二异丁腈为引发剂,乙二醇二甲基丙烯酸酯为交联剂,通过沉淀聚合法制得槲皮素分子印迹聚合物,以m(石墨+聚合物):m(石蜡)=4∶1比例混合制成的印迹聚合物修饰碳糊电极作为工作电极。在0 V富集150 s,然后从0~0.6 V以100 m V/s扫速线性扫描,记录其在0.338 V的峰电流。槲皮素物质量浓度在1.25×10-6~4.0×10-5 mol/L与峰电流呈良好的线性关系(r=0.995 0),检出限为4.72×10-8mol/L,应用该方法测定胶囊中槲皮素的含量,测得回收率为96.7%~105.6%。该修饰电极具有较高的选择性和灵敏度,可用于槲皮素的测定。     

Voltammetric determination of the synthetic pyrethroid insecticide tetramethrin in acetonitrile

The synthetic pyrethroid insecticide tetramethrin may be reduced reversibly (E°' = -1.650 V vs Ag/Ag(+)) in acetonitrile at hanging mercury drop electrodes (HMDE) and glassy carbon electrodes. On the voltammetric time scale, the initial electron-transfer process involves the reversible formation of a radical anion. Data obtained from electron paramagnetic resonance spectroscopy indicate that the unpaired electron of the radical is located within the phthalimide system of the molecule. The radical anion may be further reduced at very negative applied potentials with the number of processes being dependent on the nature of the voltammetric technique. The detection limit (3σ) for the determination of tetramethrin in acetonitrile at a glassy carbon electrode, using differential pulse voltammetry, was found to be 2.1 × 10(-6) M. At a HMDE the detection limit is lower, having a value of 9.6 × 10(-7) M. The limit of determination (10σ) at a glassy carbon electrode is 3.5 × 10(-6) M and at a HMDE is 3.0 × 10(-6) M. Tetramethrin was selectively determined in an insecticide formulation, at a glassy carbon electrode using differential pulse voltammetry, at a concentration (w/v) of 0.34 ± 0.02%. The determined concentration is in good agreement with the stated value of 0.350 ± 0.018% (w/v).     

Electrochemical behavior of vanadium in EDTA

The use of chelating agents as cleaning chemicals to remove metal deposits is gaining interest. In this study the Electrochemical behavior of vanadium in EDTA, EA and EAC solutions was studied using AC impedance technique at different immersion time. The results indicate that the values of R_ct for EA solution are higher than that for EDTA and EAC. This may be due to the presence of ascorbic acid as reducing agent. The presence of surface film is confirmed by capacitance measurements. It is shown that the capacitance is time‐dependent. Generally, the capacitance decreases with immersion time and this can be discussed on the basis that the concentration of vanadium ions at the interface increases with immersion time.     

块体非晶合金及其涂层的电化学行为

采用铜模吸铸法制备了直径为2mm的Fe58Cr12Mo7C15B6Y2和直径为4mm的Fe55Cr12Mo10Cu2C13B6Y2两种块体非晶合金.利用电弧喷涂方法将相同成分的粉芯丝材喷涂在Q235基板上.对涂层进行的结构分析表明,涂层由非晶相和晶化相共同组成,涂层中含有＜2%的孔隙.涂层和块体非晶合金电化学腐蚀研究结果表明,块体非晶合金在极化过程中发生了多次钝化现象,涂层在电化学反应过程中钝化现象比较短暂.非晶样品和涂层之间电化学性能的差异与涂层成分和结构的不均匀性有关.     

Zn-Al涂层腐蚀电化学行为研究

通过电化学交流阻抗谱(EIS)研究了Zn-Al涂层在铜加速醋酸盐雾试验中的腐蚀行为,建立了等效电路模型并分析了相关电化学参数随时间的变化规律。采用扫描电镜及能谱仪分析了涂层腐蚀后的形貌及成分组成,阐释了电化学参数的演变规律。结果表明,盐雾试验中Zn-Al涂层的腐蚀由电化学反应控制逐渐转变为扩散控制,最后进入基体腐蚀阶段。     

Electrochemical deposition and superhydrophobic behavior of ZnO nanorod arrays

Vertically aligned ZnO nanorod arrays with different heights are grown on the ZnO seeded indium tin oxide substrate by cathodic electrochemical deposition from zinc nitrate at two temperatures of 60 °C and 80 °C. As-grown ZnO nanorods exhibit wurzite crystal structure and their heights can be well controlled by different deposition times. The fluorination coating tends to induce a superhydrophobicity of ZnO nanorods, i.e., the maximal value of contact angle: 166.9°. The super water repellency can be attributed to the fact that an air layer is confined in the nanorod arrays, and thus leads to water droplets sitting on the ZnO surfaces, referring as Cassie state. Interestingly, their water contact angles are found to vary with the heights of ZnO nanorods, ranged from 99.8 to 746 nm. The superhydrophobicity of ZnO surfaces can be well predicted by a proposed model that is capable of determining the wetted fraction of ZnO pillars. This satisfactory result would shed one light on how the variation of rod height would induce the superhydrophobic behavior of ZnO nanorod arrays.     

Electrochemical determination of pharmaceuticals in spiked water samples

The electrochemical behaviour of acidic and neutral pharmaceutical active compounds (PhACs) was studied by cyclic voltammetry and pulse voltammetric techniques on mercury, carbon nanotube paste, carbon paste and gold electrodes. The best results, in terms of sensitivity, linearity range and detection limits, were obtained by differential pulse voltammetry (DPV) for ofloxacin (LOD 5.2 microM), differential pulse polarography (DPP) for clofibric acid (LOD 4.7 microM) and normal pulse voltammetry (NPV) for diclofenac (LOD 0.8 microM) and propranolol (LOD 0.5 microM). An enrichment step of approximately two orders of magnitude was performed by a solid-phase extraction procedure (SPE) in order to concentrate the samples. The developed method was optimized and tested on spiked river water samples.     

Electrochemical determination of the corrosion resistance of noble dental casting alloys

Forty-four dental casting alloys and pure metals have been evaluated for corrosion resistance in an artificial saliva. The electrochemical tests included measurement of the rest potential and tracing of polarization curves. Qualitative comparisons of the normalized polarization curves, and quantitative determination of corrosion resistance, and of corrosion and breakdown potentials, provided complementary means of evaluation. Alloys were assigned two families: alloys for crowns and bridges (C&B alloys), and alloys for ceramic veneering (PFM alloys). Among these two families, groups were based on the gold-content (high and low), and on the main non-gold component: silver for C&B alloys, and palladium for PFM alloys. Pure metals and some non-noble alloys have been included as references. From this study, it clearly appears that the PFM alloys, having a higher content of noble metals, are more corrosion resistant than the C&B alloys containing copper and silver. Some relationships between noble-metal content and electrochemical parameters such as rest potential and corrosion resistance, have been identified, but the strength of the correlations is somewhat lowered by the influence of additional parameters, such as the presence of non-noble components or the nature of the microstructure. The present investigation is part of a larger study including other electrochemical parameters as well as various biocompatiblity tests on the same set of 44 alloys.     

Electrochemical behavior of nitinol alloy in Ringer's solution

Corrosion behavior of Nitinol (nickel titanium) alloy has been examined in physiological Ringer's solution by means of electrochemical techniques (open-circuit potential measurement, potentiodynamic and potentiostatic polarizations) and capacitance measurements. The results show that the passive film is stable at open-circuit condition, but many of anodic current transients are observed at potentiodynamic and potentiostatic polarizations. The thickness of passive film decreased because of the occurrence of dissolution.     

Electrochemical behavior of Portland cement pastes containing phosphonates

An impedance measurement technique was used to investigate the effects of aminotri(methylenephosphonic acid) (ATMP), 1-hydroxyethylidene-1, 1-diphosphonic acid (HEDP), and diethylenetriaminepenta (methylenephosphonic acid) (DTPMP) on the hydration process and setting behavior of portland cement pastes. It was demonstrated that the impedance and capacitive responses can be used to characterize setting behavior and microstructural development of the hydrating pastes containing these chemical admixtures.The presence of a long induction period of up to 20 and more than 75 hours is revealed by the impedance curves of pastes containing ATMP, HEDP, and DTPMP at dosages of 0.05% and 0.2%, respectively. This confirms that phosphonates are efficient retarders. These compounds appear to have strong chelating or complexing capability, potentially poisoning CH and C-S-H nucleation. Stabilization of the C-S-H (metastable) film on the surface of cement grains appears to cause retarding effect.     

Electrochemical behavior of Mg-Al-Zn-Ga-In alloy as the anode for seawater-activated battery

The effect of indium alloying on the corrosion and discharge behaviors of Mg-Al-Zn-Ga alloys is investigated via materials characterization, immersion test and electrochemical methods. The results indicate that indium alloying can effectively modify the distribution of intermetallic phases in Mg matrix via promoting the segregation of Al in the form of Mg_(17)Al_(12) in matrix. The addition of indium can effectively activate Mg-Al-Zn-Ga alloy evidenced by increased hydrogen evolution volume and weight loss, negative shift of corrosion and discharge potentials, increase of corrosion current density, decrease of polarization resistance and promoted Faradic efficiency. Nonetheless, excessive indium alloying(2.0 wt.%) would strikingly deteriorate the electrochemical performance of Mg-Al-Zn-Ga anode due to the exorbitant active effect. The Mg-6 wt.%Al-3 wt.%Zn-1 wt.%Ga-1 wt.%In in as-cast state with acceptable corrosion rate and desirable discharge performance is a low cost, non-toxic and well-performance magnesium alloy, which is a promising anode materials for seawater-activated batteries.     

Electrochemical determination of dopamine based on self-assembled peptide nanostructure

Self-assembled peptide nanostructures are electronically insulating as are most biomaterials derived from natural amino acids. To obtain additional properties and increase the applicability of peptide nanomaterials, some chemical modifications can be performed and materials can be functionalized to form hybrid compounds. In this work, we described the formation of L-diphenylalanine nanotubes (PNTs) with cyclic-tetrameric copper(II) species containing the ligand (4-imidazolyl)ethylene-2-amino-1-ethylpyridine [Cu(4)(apyhist)(4)](4+) in the Nafion membrane on a vitreous carbon electrode surface. This copper complex has been studied as structural and functional models for the active centers of copper containing redox enzymes. Scanning electron microscopy was used to confirm the formation of the nanostructures. The electrochemical properties of the PNT-[Cu(4)(apyhist)(4)](4+)/Nafion film on a glassy carbon electrode were characterized using cyclic voltammetry and square-wave voltammetry and showed high electrocatalytic activity toward the oxidation of dopamine (DA). The detection sensitivity was found to be enhanced by the use of copper(II) complex in the PNTs/Nafion films. Under the optimum conditions, the square-wave voltammetry peak height was linearly related to the DA concentration over two concentration intervals, viz., 5.0-40 μmol L(-1) and 40-1000 μmol L(-1). The detection limit was 2.80 μmol L(-1) (S/N = 3), and ascorbic acid did not interfere with the DA detection. These results suggested that this hybrid bioinorganic system provides an attractive advantage for a new type of electrochemical sensors. The detection sensitivity was found to be enhanced by use of PNTs.     

Electrochemical behavior of p-Si/TiC in aqueous HF

The electrochemical behavior of p-Si in HF solution by modification of the silicon electrolyte interface is studied. For this purpose, the samples were coated with titanium carbide (TiC) deposited by RF pulverization of titanium under methane/argon atmosphere. The current-potential characteristics of TiC-coated electrodes in 5% HF are similar to the ones obtained with silicon. The scanning electron microscopy observation of the Si/CH_x surface structures shows that the coating is stable in HF environment but it can be destroyed upon flowing of an anodic current. The results presented suggest that a TiC film layer can be used as a potential tool for low-thickness masking and patterning. In addition, a promising class of optical filters is introduced, based on a p-Si/porous silicon/TiC.     

立方相碳化钛在锂空电池中的电化学行为

采用直流电弧等离子体法在甲烷和氩气混合气氛下原位合成碳化钛(TiC)纳米颗粒。X射线衍射、透射电子显微镜等物理表征结果显示TiC纳米颗粒粒径约为40～90 nm的立方体结构。循环伏安(CV)测试表明,TiC纳米颗粒兼具高效的氧还原和氧析出双效催化活性,可有效弥补炭材料氧析出催化活性较弱的缺陷。恒流充放电测试结果表明,相对于普通炭材料(导电炭黑,Super-P),TiC纳米颗粒催化剂可将锂空电池充电过电势降低280mV;在电流密度(i_sp)为50mA·g^-1时,首次放电比容量达1267mAh·g^-1;即使在较高的电流密度150mA·g^-1下,比容量仍保持在778mAh·g^-1,体现了良好的倍率性能。在电流密度为100mA·g^-1、限定比容量为500mAh·g^-1下,稳定循环10次。通过XRD、红外、扫描电镜表征可知,在TiC纳米颗粒的双效催化作用下,Li_2O_2的生成与分解具有良好的可逆性,有效避免了大量反应副产物积累的问题,进而提高锂空电池的电化学性能。     

Electrochemical corrosion behavior of amorphous carbon nitride thin films

The corrosion behavior along with biocompatibility and mechanical properties plays an important role in determining of biomedical implants feasibility. Diamond-like carbon seems to be the promising material in which all these three requirements can be achieved. In this study nitrogen doped amorphous carbon (a-C:N) films were deposited on silicon and medical CoCrMo alloy substrates by vacuum glow discharge sputtering technique using different deposition conditions from graphite target. Potentiodynamic polarization tests were employed to assess the corrosion performances of the films at room temperature in 0.89 wt. % NaCl solution. The influence of substrate bias on the electrochemical corrosion behavior was investigated. The highest value off E_corr for CoCrMo substrate was measured on the coating deposited with substrate bias around −0.6 kV. The shift of E_corr to more positive values was about 350 mV.     

气相色谱法快速测定杀虫气雾剂中五种拟除虫菊酯的含量

建立了一种杀虫气雾剂中五种拟除虫菊酯（胺菊酯,苯醚氰菊酯,炔咪菊酯,氯氰菊酯,氯菊酯）测定的气相色谱方法,以癸二酸二丁酯为内标,采用SE-30毛细管柱,以FID为检测器。结果在所考察的浓度范围内具有良好的线形关系,五种拟除虫菊酯相关系数大于0.9999,平均回收率为在99.7%～102.1%之间,变异系数小于2%。     

Electrochemical method for quantitative determination of trace amounts of lead

An ultrasensitive chronoamperometric method for quantitative determination of trace amounts of lead (down to 20 ppb) in acidic solutions is proposed in this paper. The method is based on observations that a complete underpotentially deposited (UPD) lead layer inhibits the electroreduction of nitrate on a bare Cu(111) electrode. To asses the limits of the method, both the electroreduction of nitrate and UPD of lead monolayer on copper single (111) and polycrystalline electrodes in perchloric acidic solution are studied by means of cyclic voltammetry, chronoamperometry, and rotating disk electrode (RDE) experiments. It is found that an inexpensive polycrystalline copper electrode is sensitive enough for analytical detection of lead traces in electrolytes down to 1 x 10(-8) M. Analytical results obtained by the proposed method in 2 orders of magnitude concentration range are compared to atomic absorption spectroscopy measurements to evaluate and assess the sensitivity of the employed experimental protocol. The excellent match between both analytical approaches validates the applicability of the proposed method.     

Electrochemical fabrication and modelling of mechanical behavior of a tri-layer polymer actuator

Stability and performance of electrochemically synthesized tri-layer polypyrrole based actuators were reported. Concentrations were optimized as 0.05 M pyrrole and 0.05 M tetrabutylammonium hexaflurophosphate in propylene carbonate (PC). The force output of the actuators ranged from 0.2 to 0.4 mN. Cyclic deflection tests on PC based actuators for a duration of 3 h indicated that the displacement decreased by 60%. However, actuation could be regenerated by immersing the actuator into the electrolyte solution. Surface resistivity measurements on the actuators prior to and after 3 h continuous deflection did not show any significant change in the resistivity of the PPy layer. A triple-layer model of the polymer actuator was developed based on the classic bending beam theory by considering strain continuity between PPy and PVDF. Results predicted by the model were in good agreement with the experimental data.