Electrochemical Determination of the Anticancer Herbal Drug Shikonin at a Nanostructured Poly(hydroxymethylated‐3,4‐ethylenedioxythiophene) Modified Electrode

A simple and sensitive method is described for the electrochemical determination of shikonin, a widely used anti‐tumoral agent, based on its electrochemical oxidation at a nanostructured poly(hydroxymethylated‐3,4‐ethylenedioxy‐thiophene) (PEDOT‐MeOH) electrode, which was fabricated by a facile electropolymerization method. Compared with bare and poly(3,4‐ethylenedioxythiophene) (PEDOT) electrodes, the PEDOT‐MeOH film exhibited a distinctly higher activity for the electrooxidation of shikonin. The PEDOT‐MeOH electrode showed a wide linear response for shikonin in the concentration range from 1.0 nM to 10.0 µM with detection limit of 0.3 nM. Furthermore, the PEDOT‐MeOH electrode displayed high stability, good reproducibility and high sensitivity for the detection of shikonin.     

Phthalocyanine-cored conductive polymer design: effect of substitution pattern and chalcogen nature on optical and electrical properties of Zn(II)-phthalocyanine–cored polycarbazoles

Phthalocyanines are one of the important candidates of tetrapyrrolic macrocycles having a π-conjugated system, and conductive polymers (CPs) have recently attracted an increasing interest as designing of new molecular materials. A smart combination of these two unique structures can produce materials with the desired properties to design various organic-molecular devices. However, fundamental principles of the design engineering for synthesis of phthalocyanine-cored CP with unique optoelectronic properties has not been investigated yet. For this purpose, tetrasubstituted peripheral or non-peripheral Zn(II)-phthalocyanine containing thioalkyl- or alkoxy-group–linked carbazoles have been synthesized. Electropolymerization of the materials under potentiodynamic conditions yielded a series of analogous donor?acceptor CPs in which the only difference was the nature of the chalcogen (O or S) and substitution pattern (peripheral or non-peripheral) on the phthalocyanine core. This was shown to have a significant impact on the optical and electrochemical properties of the CPs because of the difference in electronegativity of chalcogen and inductive effect of the substitution pattern. Here, a comprehensive investigation of the design of phthalocyanine-cored CP has been concluded to reveal structure–property relationship.     

Recent advances in electrochemical meso- and β-functionalization of porphyrins and electrografting of diazonium porphyrins

Recent studies on electrochemical meso- and β-functionalization of porphyrins and electrografting of diazonium porphyrin are presented. First, the electrochemical oxidative C–C coupling between porphyrins will be presented, followed by the intermolecular and intramolecular meso- and β-substitutions of porphyrins. Then, the latest results on diazonium porphyrin electrografting will be reviewed.     

Bilayer lipid membrane biosensor with enhanced stability for amperometric determination of hydrogen peroxide

In this paper, a polydopamine (PDA) film is electropolymerized on the surface of bilayer lipid membrane (BLM) which is immobilized with horseradish peroxidase (HRP). The coverage of the PDA film on HRP/BLM electrode is monitored by electrochemical impedance spectroscopy (EIS). The electrocatalytic reduction of H₂O₂ at the PDA/HRP/BLM electrode is studied by means of cyclic voltammetry (CV). The biosensor has a fast response to H₂O₂ of less than 5 s and an excellent linear relationship is obtained in the concentration range from 2.5 × 10⁻⁷ to 3.1 × 10⁻³ mol L⁻¹, with a detection limit of 1.0 × 10⁻⁷ mol L⁻¹ (S/N = 3). The response current of BLM/HRP/PDA biosensor retains 84% of its original response after being stored in 0.1 mol L⁻¹ pH 7.0 PBS at 4 °C for 3 weeks. The selectivity, repeatability, and storage stability of PDA/HRP/BLM biosensor are greatly enhanced by the coverage of polydopamine film on BLM.     

A disposable electrochemical sensor for the determination of indole-3-acetic acid based on poly(safranine T)-reduced graphene oxide nanocomposite

A disposable electrochemical sensor for the determination of indole-3-acetic acid (IAA) based on nanocomposites of reduced graphene oxide (rGO) and poly(safranine T) (PST) was reported. The sensor was prepared by coating a rGO film on a pre-anodized graphite electrode (AGE) through dipping-drying and electrodepositing a uniform PST layer on the rGO film. Scanning electron microscopic (SEM) and infrared spectroscopic (IR) characterizations indicated that PST-rGO formed a rough and crumpled composite film on AGE, which exhibited high sensitive response for the oxidation of IAA with 147-fold enhancement of the current signal compared with bare AGE. The voltammetric current has a good linear relationship with IAA concentration in the range 1.0 × 10⁻⁷-7.0 × 10⁻⁶ M, with a low detection limit of 5.0 × 10⁻⁸ M. This sensor has been applied to the determination of IAA in the extract samples of several plant leaves and the recoveries varied in the range of 97.71-103.43%.     

Surface‐Confined Electropolymerization of Methylene Blue on Gold Electrodes

We report on the electrochemical behaviour and electropolymerization of self‐assembled monolayers (SAMs) of methylene blue (MB) on gold electrodes. The SAMs of MB on gold electrodes were prepared by immersing the substrates into a solution of 1.0 mM MB in absolute ethanol for different times at room temperature. Cyclic voltammetry experiments exhibited that reductive desorption of MB monolayer takes place at three different potentials on polycrystalline gold electrodes, while reductive desorption of MB monolayer consists of only one peak on single crystal Au(111) substrates. Calculated charge densities for different immersion times indicated that optimal immersion time for self‐assembly of MB is 96 h. Electropolymerization of SAMs of MB on gold electrode was achieved by applying 0.95 V for 1 s in 0.1 M borate buffer solution (pH: 9.0). It was observed that poly(MB) monolayers are highly stable in acidic media. ATR‐FTIR and UV‐vis spectra exhibited differences between monomer and polymer monolayers, which are attributed to surface‐confined electropolymerization. STM image of poly(MB) monolayer on Au(111) substrate revealed a surface that is covered by well‐ordered, collateral nanowires with an average size of 3 nm.     

Synthesis and characterization of porphyrin electrochromic and photovoltaic electropolymers

New asymmetric porphyrins, with electroactive functionalities were synthesized. 5,15-Bis[4(-N,N-diphenylamino)phenyl]-10,20-bis[3-(N-ethylcarbazoyl)]porphyrin and its Zn(II) derivative allow the electrochemical formation of conjugated, conducting and stable polymeric films over semitransparent indium-tin oxide surface. The spectral changes observed upon oxidation of the films produced different colorations. The polymeric materials showed the generation of photoinduced charge separation states and charge migration upon porphyrin excitation, making them promising candidates for application in optoelectronics devices.     

苯酚苯胺共聚物在304不锈钢电极表面的电化学合成及成膜微观结构分析

Electrochemical copolymerization of phenol and aniline was achieved on 304 stainless steel anodes in neutral water solution with an electrolyte of Na₂SO₄O₄. Compared with pit corro-sion potential of different copolymer coatings, the best solution composition was 0.09 mol/L phenol and 0.01 mol/L aniline. Through infrared spectrum analysis, polyaniline structure was proved in phenol-aniline copolymer, as well as more side chains. Scanning electron mi-croscope was used to analyze microstructure of copolymer coating, taking advantage of part solubility of phenol-aniline copolymer in tetrahydrofuran, the bifurcate network structure was observed. The copolymer coating microstructure was summarized, compared with the performance of polyphenol coatings, the reasons of corrosion resistance enhancement with the addition of aniline in electropolymerization reaction was assumed as well.     

多巴胺在牛磺酸修饰玻碳电极上的电化学行为及其分析应用

采用电化学聚合法制备了牛磺酸修饰玻碳电极,研究了多巴胺在聚牛磺酸修饰电极上的电化学行为,建立了测定痕量多巴胺的新方法.在pH 7.2的磷酸盐缓冲溶液中,多巴胺在修饰电极上产生一对灵敏的氧化还原峰,采用差分脉冲伏安法测定,其氧化峰电流与多巴胺浓度在8.0×10-8～1.0×10-4 mol/L范围内呈良好的线性关系,检出限为1.0×10-8 mol/L.     

苯二胺对聚苯胺电化学合成及其降解的影响

运用循环伏安法和紫外 可见吸收光谱分别研究了邻、间、对 3种苯二胺单体对苯胺聚合及其生成膜降解过程的影响 .结果表明 ,对苯二胺在催化苯胺聚合的同时加速了膜的降解 ,而邻、间苯二胺对聚合与膜的降解均起抑制作用 .这可能是由于 3种苯二胺结构的不同影响了聚合机理 ,并在一定程度上改变了膜的化学物理性质所致 .扫描电镜显示 ,苯二胺的加入对聚合膜的形态结构也有明显影响 ,与纯聚苯胺膜相比 ,共聚膜变得更加致密、光滑 .