对苯二酚在碳纳米管修饰玻碳电极的电化学行为及电化学动力学研究

碳纳米管(Carbon Nanotubes,CNT)自1991年发现以来,因其结构所具有的高比表面,高电导率,稳定的化学性质与超常的机械强度已成为世界范围内的研究热点,并应用于催化、气体储藏和电极材料等领域。用CNT修饰的电极具有良好的电化学性能并且已经取得了很好的实验结果[1],因此研究碳     

细胞色素C在离子液体修饰电极上的电化学行为

分别合成了疏水和亲水性咪唑类离子液体,并制备了相应的两种离子液体修饰的玻碳电极。循环伏安法测量结果显示,细胞色素C在离子液体修饰的玻碳电极上的电子传递过程为一扩散控制的准可逆反应,表明咪唑类离子液体也可用作细胞色素C电子传递的有效促进剂。电化学交流阻抗谱的测量结果得到了与循环伏安相同的结论。     

Copper hexacyanoferrate multilayer films on glassy carbon electrode modified with 4-aminobenzoic acid in aqueous solution

4-Aminobenzoic acid (4-ABA) was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation during the electrooxidation process in 0.1 M KCl aqueous solution. X-ray photoelectron spectroscopy (XPS) measurement proves the presence of 4-carboxylphenylamine on the GCE. Electron transfer processes of Fe(CN)₆³⁻ in solutions of various pHs at the modified electrode are studied by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Changing the solution pH would result in the variation of the terminal group's charge state, based on which the surface pK_a values were estimated. The copper hexacyanoferrate (CuHCF) multilayer films were formed on 4-ABA/GCE prepared in aqueous solution, and which exhibit good electrochemical behavior with high stability.     

胡椒碱在碳纳米管修饰电极上的电化学行为研究

研究了胡椒碱在碳纳米管修饰电极上的电化学行为,在pH为6.4的磷酸盐缓冲溶液中,胡椒碱在-1.12V(vs.SCE)处有一灵敏的还原峰.与裸电极相比,还原峰电位明显正移,峰电流显著增加,表明该修饰电极对胡椒碱的还原反应具有明显的催化作用.峰电流与胡椒碱的浓度在10-6～10-5mol/L范围内呈良好的线性关系(r=0.995),检出限为2.0×10-7mol/L.同时,计算了电荷转移数和扩散系数,考查了修饰电极的重现性,7次平行测量的RSD为4.96%.     

The electrochemical reaction mechanism of selenocystine on selenium-gold film modified glassy carbon electrode

A simple and selective voltammetric method based on selenium-gold film modified glassy carbon electrode has been developed for investigating electrochemical reaction mechanism of selenocystine. With N₂ saturated, redox reactions between selenocystine (SeC) and selenocysteine (SeCys) were judged to be two simple electron-transfer processes. With air saturated, the reduction reaction was diagnosed to be EC catalytic reaction (the chemical oxidation reaction of the SeCys by O₂ (C) following the electron-transfer reaction (E)) and oxidation reaction is a simple electron-transfer process. With pure O₂ saturated, only reduction peak was observed and the reaction was judged to be EC catalytic reaction. The electron-transfer numbers of redox reaction were calculated to be 2 by chronocoulometry and rotating disk electrode.     

对氯酚在碳纳米管修饰玻碳电极上的电化学行为研究

研究了对氯酚在多壁碳纳米管修饰玻碳电极（MWNTs/GC）上的电化学行为。MWNTs/GC电极对对氯酚具有良好的电催化作用,相比玻碳电极对氯酚的氧化峰电位负移76 mV,峰电流达到玻碳电极上的8倍。通过线性扫描伏安法研究了富集时间、溶液pH和扫描速率对对氯酚氧化的影响。并采用计时电流法研究了氧化峰电流与对氯酚的浓度关系,结果显示峰电流与对氯酚的浓度在2.0×10^-7-2.0×10^-4mol/L范围内呈良好线性关系,检出限为8.8×10-8mol/L（S/N=3）。放置7 d后,对氯酚在碳纳米管上的峰电流仍能达到最初电流的96.2%,表明电极的稳定性较好。     

盐酸阿霉素在玻碳电极上的电化学行为研究及分析应用

采用线性扫描伏安法和循环伏安法研究了盐酸阿霉素在玻碳电极上的电化学行为及电极反应机理,优化了测定盐酸阿霉素的各实验参数。结果表明,在0.01 mol/L的HCl溶液中,盐酸阿霉素在-0.40 V处出现(vs.SCE)一灵敏的还原峰,峰电流与其溶液浓度在5.0×10-8~1.0×10-6mol/L(r=0.999)和1.0×10-6~1.0×10-5mol/L(r=0.998)范围内呈良好的线性关系,检出限为1.0×10-8mol/L。并用循环伏安法研究了盐酸阿霉素的峰电流性质,发现电极反应属于准可逆过程,出现一对灵敏的氧化还原峰,体系属准可逆吸附波。利用盐酸阿霉素在玻碳电极的电化学行为建立的分析方法可用于盐酸阿霉素的质量监控及药代动力学研究。     

单层碳纳米管修饰电极上盐酸曲普利啶的电化学行为及其应用研究

应用循环伏安法研究了盐酸曲普利啶在碳纳米管修饰电极上的电化学行为.结果表明:在0.1 mol/L磷酸盐缓冲溶液(pH 6.9)中,盐酸曲普利啶产生一灵敏的氧化峰,其峰电位为0.81 V(vs.Ag/AgCl),峰电流与盐酸曲普利啶在1.0×10-6～1.3×10-4 mol/L浓度范围内呈线性关系,检出限为5.0×10-7mol/L,已用于片剂中盐酸曲普利啶的测定.     

Chemically modified glassy carbon electrode for electrochemical sensing paracetamol in acidic solution

Different organic molecules were covalently grafted on glassy carbon electrodes (GCEs) by an electrochemical reduction or potentiostatic process of several in situ-generated diazonium cations in acidic aqueous solution containing NaNO₂. The cyclic voltammetry implemented in 0.1?M KCl aqueous solution containing 5?mM Fe(CN) ₆ ^3? or Ru(NH₃) ₆ ³⁺ confirmed the blocking properties of the modified GCEs. The electrochemical impedance spectroscopy (EIS) performed in 0.1?M KCl aqueous solution containing 5?mM Fe(CN) ₆ ^3?/4? was used to measure the surface coverage of the modifiers on GCE; the results showed that the modified layers on GCEs are very compact. The linear sweep voltammetry (LSV) was employed to investigate the electrochemical sensing properties of the bare and modified GCEs toward paracetamol (PCT) in sulfuric acid solution of pH?1.02, and the corresponding calibration plots were obtained, respectively. The results indicated there is an oxidation peak of PCT in the linear sweep voltammograms on the bare and modified GCEs with the active terminal groups such as ?OPO₃H₂, ?SO₃H, ?COOH, and so on, but do not appear on GCEs modified with the inert terminal groups such as ?NO₂ and ?Br. These imply that the GCEs modified with the active terminal groups display an electrochemical behavior like bulk GCE; however, those with the inert terminal groups present an electrochemical behavior like microelectrode. The varying electrochemical sensitivity of all the electrodes toward PCT was explained according to electronegativity and pK _a of the terminal groups of the modifiers on the electrodes and hydrogen bond between the modifiers and PCT. Apparent standard rate constants of PCT oxidation reaction on the bare and modified GCEs were obtained from the Laviron’s approach.     

Electrochemical reduction of nitroprusside on a glassy carbon electrode modified by poly-l-lysine films

The present work describes the preparation and characterization of polyelectrolyte coatings of poly-l-lysine (PLL) to modify a glassy carbon electrode and its application to the pre-accumulation of nitroprusside (NP). The effects of the coating on the electrochemical reduction of NP were investigated. The performance of the modified electrode indicates that the drug can be immobilized by electrostatic interaction and the voltammetric signal monitored at all pH values in the range of 2–12. The strong interaction between NP and PLL stabilizes the complex on the electrode surface and minimizes the chemical reaction of lost CN⁻ ions as a subsequent reaction of electron transfer, which could improve the action mechanism of NP.     

Hydrazine sensors development based on a glassy carbon electrode modified with a nanostructured TiO2 films by electrochemical approach

Microchimica Acta - The authors describe a selective hydrazine sensor that is based on the use of a film of TiO2 nanoparticles faceted predominantly at the 101 and 001 sides. The hydrazine (Hyd)...     

Enhanced electrochemical detection of ketorolac tromethamine at polypyrrole modified glassy carbon electrode.

A glassy carbon electrode modified with a coating of polypyrrole (Ppy) exhibited an attractive performance for the detection and determination of a non-steroidal and non-narcotic analgesic compound, ketorolac tromethamine (KT). Cyclic voltammetry, differential pulse and square wave voltammetry were used in a combined way to identify the electrochemical characteristics and to optimize the conditions for detection. For calibrating and estimating KT, square-wave voltammetry was mainly used. The drug shows a well-defined peak at -1.40 V vs. Ag/AgCl in the acetate buffer (pH 5.5). The existence of Ppy on the surface of the electrode gives higher electrochemical active sites at the electrode for the detection of KT and preconcentrate KT by adsorption. The square-wave stripping voltammetric response depends on the excitation signal and the accumulation time. The calibration curve is linear in the range 1 x 10(-11) to 1 x 10(-7) M with a detection limit of 1.0 x 10(-12) M. Applicability to serum samples was also demonstrated. A detection limit of 1.0 ng ml for serum was observed. Square-wave voltammetry shows superior performance over UV spectroscopy and other techniques.     

The electrochemical behavior of dopamine at glassy carbon electrode modified by Nafion multiwalled carbon nanotubes

DFT (B3LY/6-31G (d, p) and B3LYP/cc-PVDZ) calculations are performed for deoxidized dopamine (DA_(R)) and its oxidized form (DA_(O)). The electrochemistry of dopamine (DA) was studied by cyclic voltammetry (CV) at a glassy carbon electrode modified by Nafion multiwalled carbon nanotubes (MWNTs) in phosphate buffers at pH 5.4, showing that the standard electrode potential of a half reaction for DA_(O), H⁺/DA_(R) is 0.74 V. This experimental standard electrode potential of the half reaction is consistent with those of 0.65 and 0.69 V calculated using the energies of solvation and the sum of the electronic and thermal free energies of DA_(R) and DA_(O). The frontier orbital theory and Mulliken charges of molecules explain the electrochemical behavior of CV at a modified electrode well. The effects of oxygen on DA_(R) in blood and drug are also discussed according to equilibrium theory. The modified electrode was successful for determination of the content of pharmaceutical DA. The text was submitted by the authors in English.     

羟胺在碳纳米管修饰玻碳电极上的电催化还原及电化学动力学性质研究

研究了羟胺在碳纳米管修饰玻碳电极(CNT/GC)上的电化学行为。研究结果表明,碳纳米管对羟胺的电化学行为有良好的电催化作用,在-0.62 V有一还原峰,是羟胺获得2个电子还原为铵所形成,同时测定了该电化学过程的动力学参数:电子转移数n为2,电子转移系数α为0.287,电极反应速率常数k为1.35×10-3cm/s。     

Characterization of modified glassy carbon films

The composition and structure of the thin conversion films at pre- and breakdown state are investigated. The breakdown leads to a modified structure and composition. Raman spectra of modified films show the formation of glassy carbon with a defined size of crystallites. A typical morphology characterized by a strong structured surface indicates this breakdown state. Electron diffraction patterns of the pre-breakdown state show the presence of titanium nitride, titanium carbide and titanium oxide.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Electrochemical behavior and determination of clozapine on a glassy carbon electrode modified by electrochemical oxidation.

The adsorptive and electrochemical behaviors of clozapine (CLZ) were investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to 1.0 V vs. Ag/AgCl reference electrode. Based on the obtained electrochemical results, an electrochemical-chemical (EC) mechanism was proposed to explain the electrochemical oxidation of CLZ. The resulting electrochemically pretreated glassy carbon electrode (EPGCE) showed good activity to improve the electrochemical response of the drug. CLZ was accumulated in a phosphate buffer (pH 6) at a certain time, and then determined by differential pulse voltammetry. The anodic and cathodic peak currents showed a linear function in the concentration ranges of 0.1 - 1, 1 - 10 and 10 - 100 microM with various accumulation times. The proposed method was successfully used for the determination of CLZ in pharmaceutical preparations. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine samples with satisfactory results. The recovery levels of the method reached 96% (RSD, 1.8%) and 90% (RSD, 2.8%) for urine and plasma samples, respectively.     

苦参碱在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电分析方法

研究了苦参碱(Matrine, MT) 在多壁碳纳米管修饰玻碳电极(MWCNT/GCE)上的电化学行为. 与GCE相比, MT在MWCNT/GCE上峰电位负移120 mV, 峰电流增大约2.5倍, 表明MWCNT/GCE对MT的电化学氧化具有良好的催化作用. 同时测定并计算了MT在MWCNT/GCE上的电极过程动力学参数: 电子转移系数α、电极反应速率常数ks、扩散系数D. 运用差分脉冲伏安法对苦参碱样品含量进行测定, 相对标准偏差为0.12%～2.9%, 加标回收率为98.4%～99.0%. 该方法可用于MT的电化学定量测定.