富勒烯C_(60)/离子液体复合物修饰电极对苋菜红的方波伏安检测

制备了富勒烯C_(60)/离子液体复合物修饰的纳米碳糊电极,建立了一种灵敏、快速检测苋菜红的新分析方法;利用循环伏安法(CV)对修饰电极进行了表征;利用方波伏安法(SWV)研究了苋菜红的电化学行为;根据不同扫速下的峰电流与扫速的关系讨论了苋菜红在电极表面的反应过程;优化了实验条件,讨论了干扰物质的影响。结果表明,富勒烯C_(60)/离子液体复合物修饰纳米碳糊电极对苋菜红表现出较好的选择性和较高的灵敏度,在最优的实验条件下,利用方波伏安法定量检测苋菜红,苋菜红的峰电流与浓度在0.5～20μmol/L之间呈线性关系(R²=0.990 6),检测限为0.1μmol/L(S/N=3);干扰研究表明,大部分干扰物质对苋菜红的检测无明显影响(相对标准偏差<±5%)。本实验制备的电化学传感器可用于实际样品的检测,样品回收率为95.0%～103.2%。     

修饰纳米碳离子液体糊电极对双酚A的电催化氧化研究

采用组合法构建了羧基化介孔分子筛修饰纳米碳离子液体糊电极,运用循环伏安法研究了双酚A在该修饰电极上的电化学行为。通过对扫速的研究讨论了双酚A在修饰电极表面的反应过程;讨论了pH值、修饰剂含量以及富集时间对双酚A电流响应的影响。在最优的实验条件下,修饰电极对双酚A具有良好的电催化氧化活性,BPA浓度在0.1～50μM时,峰电流与浓度有很好的线性关系。当信噪比为3时,检测限为0.05μM。     

离子液体-石墨烯修饰碳纤维微电极电化学研究

实验制备了离子液体-石墨烯修饰碳纤维微电极,采用循环伏安法和差分脉冲伏安法测定对乙酰氨基酚(ACOP)在该修饰电极上的电化学行为。结果显示,修饰后电极的稳定性和重现性明显增加。ACOP在修饰电极上的氧化峰电流与扫速的平方根基本成正比,氧化过程受扩散控制。采用差分脉冲伏安法测定ACOP标准品梯度浓度溶液,在5×10-7~1×10-4mol/L浓度范围内,其氧化峰电流与其浓度呈现良好的线性关系良好。     

多巴胺在纳米金/玻碳微球/离子液体复合电极上的电化学行为及测定

通过组合法构建了纳米金/玻碳微球/离子液体复合电极(Au@GCILE),采用方波伏安法(SWV)研究多巴胺(DA)在该电极上的电化学行为,讨论多巴胺在电极表面的反应过程。结果表明,与普通碳离子液体电极相比,多巴胺在纳米金/玻碳微球/离子液体复合电极(Au@GCILE)上的峰电流显著增加,说明复合材料对多巴胺具有更好的电催化活性。在优化的条件下,DA的氧化峰电流与其溶液浓度在0. 5³00μmol/L范围内呈良好的线性关系(r2=0. 991 6),检测限为0. 1μmol/L。该电极具有良好的重现性与选择性,可用于实际样品中DA的检测。     

姜黄素在乙炔黑-离子液体复合修饰玻碳电极上的电化学行为及含量的测定

采用乙炔黑(AB)和离子液体(1-丁基-3-甲基咪唑六氟磷酸盐,[BMIM]PF₆)作为复合修饰材料,制备了AB-离子液体复合修饰电极(AB-[BMIM]PF₆/GCE)。用循环伏安法(CV)研究姜黄素在该修饰电极上的电化学行为。实验结果表明,在pH为6.5的磷酸盐缓冲液(PBS)中,姜黄素在该修饰电极上出现氧化峰。AB-离子液体分散液的最佳滴涂量为8μL,此时姜黄素检测的峰电流值最大且灵敏。在扫速为75 mV·s^-1时,峰电流变化最大,表明此为最佳扫描速率。此时,峰电流值与姜黄素浓度呈线性关系,其线性方程为I(μA)=3.121 5C(mmol·L^-1)+0.789 7,检测限为0.02 mmol·L^-1。     

核黄素(VB2)在液体石蜡碳糊电极上的伏安特性及脉冲伏安法测定

以液体石腊碳糊电极为工作电极,在0.1 mol/L NaCl(pH=2.5)底液中研究VB2的伏安特性.VB2有一对氧化还原峰,峰电位为氧化峰(I)-110 mV/还原峰(Ⅱ)-160 mV,结果表明溶液中VB2的电极过程主要受VB2表面吸附控制.VB2溶液受光照后,增加一对光色素的氧化还原峰,其峰电位为氧化峰(Ⅳ)-220mV/还原峰(Ⅲ)-280 mV.采用微分脉冲伏安法进行VB2的定量分析,线性范围为1×10-5～6.0×10-8moL/L,检测下限为2.00×10-8moL/L.测定复合VB药片中的VB2,RSD为2.1%,回收率为96.8～104%,其结果与药典中标准方法测定结果一致.     

铬(Ⅵ)的方波伏安行为和测定

在0.1mol/L的氨水缓冲溶液(pH=10.0)中,铬(VI)离子于-1.45V(vsS.C.E)出现一灵敏的方波伏安峰。峰电流Ip与Cr(Ⅵ)的质量浓度在0.1~2.0×103mg/L范围内呈现良好的线性关系,其相关系数为0.9886,检出限为0.05mg/LCr(Ⅵ),方法的标准偏差为2.8%。该法应用于实际样品电镀铬液及其废液中铬(Ⅵ)含量的测定,结果表明:与标准方法二苯碳酰二肼分光光度法比较,本法不需要加入特定的试剂而直接水样测定,简单快速。     

基于碳纳米管-离子液体复合电极的双酚A传感器研究

构建了一种基于碳纳米管-离子液体复合电极的双酚A（BPA）传感器。采用循环伏安法和线性扫描伏安法（LSV）研究了双酚A在该修饰电极上的电化学行为,并对实验条件进行了优化。在最佳条件下,BPA的氧化峰电流与其浓度在0.5-100μM范围内有良好的线性关系（r^2=0.9980）,检出限为0.1μM（S/N=3）。此方法能应用于湖水和塑料袋中BPA的测定,回收率在96.20%-105.20%之间。     

“方波脉冲伏安法检测水中铋”教学实验精密度的影响因素探究

我们对影响阳极溶出方波脉冲伏安法测量精密度的因素进行探究。结果显示：搅拌速度、抛光时间、超声时间、电化学清洗时间对结果精密度影响较大。根据正交实验,这四个因素对精密度的影响为：超声时间>搅拌速度>抛光时间>清洗时间。在选定的优化条件下,对浓度为10μmol/L,5μmol/L,1μmol/L铋标准样品分别平行测定5次的相对标准偏差为2.0%,2.5%,3.4%。优化后的实验方案操作更加精确、规范,更有利于学生掌握此项测试技术。     

离子液体季铵盐悬液电极检测碱性废水pH值新方法研究

以加入一定量的季铵盐和离子液体的4-甲基-2-戊酮(MIBK)作为有机相,研究了一种测定碱性废水pH值的液/液界面电化学分析新方法。利用循环伏安法测试了OH-在液/液界面处的反应,实验证明该过程受扩散作用控制,并阐述了可能的机理。当季铵盐浓度达到0.05 g/mL时,液/液界面处OH-的交换能够达到饱和,峰电流大小由OH-浓度控制。同时还研究了温度对该体系的影响。OH-的峰电位在0.6 VvsSCE处,并且pH值在7~12范围内与峰电流成正比。对实际酞菁蓝染料废水的pH值进行检测,能够达到较好的准确度。     

Electrochemical behaviors of thymine on a new ionic liquid modified carbon electrode and its detection

A new electrochemical method was proposed for the determination of thymine, which relied on the oxidation of thymine at a carbon ionic liquid electrode (CILE) in a pH 5.0 Britton-Robinson buffer solution. CILE was fabricated by using ionic liquid 1-(3-chloro-2-hydroxy-propyl)-3-methylimidazole acetate as the binder, which showed strong electrocatalytic ability to promote the oxidation of thymine. A single well-defined irreversible oxidation peak appeared with adsorption-controlled process and enhanced electrochemical response on the CILE, which was due to the presence of high conductive ionic liquid on the electrode. The reaction parameters of thymine were calculated with the electron transfer coefficient (α) as 0.27, the electron transfer number (n) as 1.23, the apparent heterogeneous electron transfer rate constant (k_s) as 6.87 × 10⁻⁶ s⁻¹ and the surface coverage (Г_T) as 5.71 × 10⁻⁸ mol cm⁻². Under the selected conditions the oxidation peak current was proportional to thymine concentration in the range from 3.0 to 3000.0 μM with the detection limit as 0.54 μM (3σ) by differential pulse voltammetry. The proposed method showed good selectivity to the thymine detection without the interferences of coexisting substances.     

Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode, ionic liquid modified carbon paste electrode and carbon paste electrode

Ionic liquid, 1-heptyl-3-methylimidazolium hexafluorophosphate (HMIMPF₆), has been used to fabricate two new electrodes, carbon ionic liquid electrode (CILE) and ionic liquid modified carbon paste electrode (IL/CPE), using graphite powder mixed with HMIMPF₆ or the mixture of HMIMPF₆/paraffin liquid as the binder, respectively. The electrochemical behaviors of hydroquinone at the CILE, the IL/CPE and the CPE were investigated in phosphate buffer solution. At all these electrodes, hydroquinone showed a pair of redox peaks. The order of the current response and the standard rate constant of hydroquinone at these electrodes were as follows: CILE > IL/CPE > CPE, while the peak-to-peak potential separation was in an opposite sequence: CILE < IL/CPE < CPE. The results show the superiority of CILE to IL/CPE and CPE, and IL/CPE to CPE in terms of promoting electron transfer, improving reversibility and enhancing sensitivity. The CILE was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of hydroquinone in medicated skin cosmetic cream.     

Direct electrochemistry of double strand DNA on ionic liquid modified screen-printed graphite electrode

An ionic liquid modified screen-printed graphite electrode (SPE) was used for direct electrochemistry of herring sperm double strand DNA (dsDNA) by voltammetry. Due to the high conductivity of ionic liquid n-octylpyridinum hexafluorophosphate (OPPF), this electrode exhibited excellent electrochemical activity for the oxidation of dsDNA. Two irreversible oxidation peaks were obtained at the developed electrode, which corresponded to the oxidation of guanine and adenine residues present in the dsDNA. The basic electrochemical behavior of dsDNA at the OPPF modified SPE was carefully investigated. Combined with the differential pulse voltammetry, this electrode exhibited a good linear range from 20 μg mL⁻¹ to 120 μg mL⁻¹ with a detection limit of 5 μg mL⁻¹ for the direct determination of dsDNA. Furthermore, the OPPF modified electrode displayed high reproducibility and stability for the dsDNA determination.     

Direct electrochemistry of guanosine on multi-walled carbon nanotubes modified carbon ionic liquid electrode

A multi-walled carbon nanotubes (MWCNTs) modified carbon ionic liquid electrode (CILE) was fabricated and used to investigate the electrochemical behavior of guanosine. CILE was prepared by mixing hydrophilic ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄), graphite powder and liquid paraffin together. The fabricated MWCNTs/CILE showed great electrocatalytic ability to the oxidation of guanosine and an irreversible oxidation peak appeared at 1.067 V (vs. SCE) with improved peak current. The electrochemical behavior of guanosine on the MWCNTs/CILE was carefully studied by cyclic voltammetry and the electrochemical parameters such as the charge transfer coefficient (α) and the electrode reaction standard rate constant (k_s) were calculated with the result as 0.66 and 2.94 × 10⁻⁴ s⁻¹, respectively. By using differential pulse voltammetry (DPV) as the detection method, a linear relationship was obtained between the oxidation peak current and the guanosine concentration in the range from 1.0 × 10⁻⁷ to 4.0 × 10⁻⁵ mol/L with the detection limit as 7.8 × 10⁻⁸ mol/L (3σ). The common coexisting substances showed no interferences to the guanosine detection and the modified electrode showed good ability to distinguish the electrochemical response of guanosine and adenosine.     

Electrocatalytic oxidation of formaldehyde on nickel modified ionic liquid carbon paste electrode as a simple and efficient electrode

Ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was used to fabricate a new ionic liquid/carbon paste electrode (IL/CPE). The general behavior of this electrode was characterized by electrochemical impedance spectroscopy, cyclic voltammetry, and scanning electron microscopy. Results showed that the IL plays an important role in improving the conductivity, reversibility, and electron transfer rate of the electrode. Nickel-modified ionic liquid/carbon paste electrode (Ni/IL/CPE) was also constructed by immersion of the IL/CPE in 1.0 M nickel sulfate solution. IL showed significant effect on the accumulation of nickel species on the surface of the electrode. The Ni/IL/CPE was applied successfully to highly efficient (current density of 16.5 mA cm⁻²) electrocatalytic oxidation of formaldehyde in alkaline medium. Cyclic voltammetry and chronoamperometry techniques indicated that this electrode displays a considerable electrocatalytic activity toward the oxidation of formaldehyde. The effects of different scan rates and formaldehyde concentrations on the electrocatalytic activity of this modified electrode were investigated. Finally, the rate constant for chemical reaction between formaldehyde and redox sites of the electrode was calculated.     

Square wave voltammetric determination of methiocarb insecticide based on multiwall carbon nanotube paste electrode

Cyclic voltammogram of methiocarb in 0.1 M H₂SO₄ exhibited an irreversible anodic peak at about +1285 mV versus Ag/AgCl. Electro-oxidation and determination of methiocarb in spiked soil, river water and agrochemical formulation were realized on a newly prepared carbon-nanotube paste electrode by applying square wave voltammetry (SWV). The dE _p /dpH value indicated that the oxidation mechanism involved the coupling of H⁺ with the oxidation process. The peak signals were linearly related to methiocarb concentration in the range of 1.5–59.1 mgL^?1 with a detection limit of 0.45 mgL^?1. The accuracy and selectivity of the proposed method were shown by calculating the recoveries of methiocarb from soil, river water and pesticide formulation Mesurol^®. The calculated percent recoveries for soil and river water samples spiked with 30.0 μg g^?1 and 40.0 μg mL^?1 levels were 99.3 ± 1.2 and 98.5 ± 0.3 at 95 % confidence limit, respectively.     

Simultaneous determination of catechol and hydroquinone based on poly(sulfosalicylic acid)/functionalized graphene modified electrode

A glassy carbon electrode (GCE) modified with poly(sulfosalicylic acid) (PSA) and poly(diallyldimethylammonium chloride)-graphene (PDDA-GN) was prepared by a simple self-assembly method. The formation of films was ascribed to the electrostatic force between negatively charged PSA and positively charged PDDA-GN as well as the π–π stacking interaction between PSA and PDDA-GN. The as prepared films were characterized by scanning electron microscopy (SEM), Raman spectroscopy and electrochemical methods. Under the optimized condition, the modified GCE showed two well-defined redox waves for catechol (CT) and hydroquinone (HQ) in cyclic voltammetry (CV) with a peak potential separation of 111 mV, which ensured the anti-interference ability of the electrochemical sensor and made simultaneous determination of dihydroxybenzene isomers possible in real samples. The corresponding oxidation currents increased remarkably compared with those obtained at the bare GCE, PSA/GCE and PDDA-GN/GCE, respectively. Differential pulse voltammetry (DPV) was used for the simultaneous determination of CT and HQ. The anodic peak current of CT was linear in the concentration from 1 × 10^?6 to 4 × 10^?4 M in the presence of 3 × 10^?5 M HQ, and the detection limit was 2.2 × 10^?7 M (S/N = 3). At the same time, the anodic peak current of HQ was linear in the concentration from 2 × 10^?6 to 4 × 10^?4 M in the presence of 2 × 10^?5 M CT, and the detection limit was 3.9 × 10^?7 M (S/N = 3). The proposed method was applied to simultaneous determination of CT and HQ in tap water with satisfactory results. These results indicated that PSA/PDDA-GN is a promising modified material with great potential in electrocatalysis and electrochemical sensing.     

Disposable screen-printed antimony film electrode modified with carbon nanotubes/ionic liquid for electrochemical stripping measurement

In this paper, two disposable screen-printed antimony film electrodes (SPSbFEs) modified with multi-walled carbon nanotubes (MWCNTs) and ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄), respectively for electrochemical stripping measurement are introduced. The modified screen-printed electrode substrate was prepared by homogeneously doping the attractive material into the graphite-based printing ink, and then an antimony film was in situ formed by simultaneously electrodepositing the antimony precursor with interesting analytes on the modified substrate. The electroanalytical performance of the modified SPSbFE for heavy metals based on the anodic stripping protocol was intensively evaluated. It was found that stripping voltammetric measurements of mercury (II) and lead (II) at the modified SPSbFEs resulted in good peaks with very low background contribution. In comparison with the bare SPSbFE, the modifications of both MWCNTs and [Bmim]BF₄ were demonstrated providing more sensitive responses. The results indicated that the SPSbFE modified with 4 wt% [Bmim]BF₄ exhibited well linear behavior in the mercury (II) concentration range from 20 to 140 μg/L (R² = 0.998) with a detection limit of 0.36 μg/L (S/N = 3) under a 120 s accumulation, and good repeatability with a relative standard deviation (RSD) of 4.16% (40 μg/L, n = 12). The proposed electrodes, as new styles of “mercury-free” electrodes, also exhibit encouraging properties for measurements of practical samples.     

Study on poly(ether ether ketone)/organically modified montmorillonite composites

Abstract

Novel poly(ether ether ketone) (PEEK)/organically modified montmorillonite (OMMT) composites containing 0–10 wt-% fractions of OMMT were prepared by melting blending method and the microstructure, thermal and mechanical properties were investigated using different characterisation techniques. X-ray diffraction and transmission electron microscopy showed that the OMMT was well dispersed with microscale in the PEEK matrix. Differential scanning calorimetry indicated that the glass transition temperature T _g and melt temperature T _m of PEEK/OMMT composites (POMCs) were hardly affected by the addition of OMMT, while the crystal temperature T _c decreased when the amount of OMMT excessed 1 wt-%. The data of thermogravimetric analysis exhibited that the thermal stability of POMCs in higher temperature region was better than that of pure PEEK. The results of mechanical properties test revealed that modulus and strength of POMCs increased with the content of OMMT, whereas the elongation at break and impact strength of POMCs decreased.