Towards hybrid carbazole/pyrrole-based carboxylated monomers: chemical synthesis, characterisation and electro-oxidation properties

Six novel hybrid carbazole (Cbz)-pyrrole (Pyr)-based carboxylated monomers were synthesised and unambiguously characterised using common spectroscopic tools. Clauson-Kaas, amide coupling, LAH (lithium aluminium hydride)-mediated reduction, esterification and debenzylation reactions were used as key chemical reactions towards their multi-step synthesis. The electro-oxidation features of all these six hybrid Cbz/Pyr-monomers were investigated for the electro-deposition of corresponding polyCOOH conducting coatings. Quite interestingly, and due to the fact that such electro-oxidisable monomers contain both types of oxidisable heterocycles, that is, Pyr and Cbz species, it was found that the successful electro-polymerisation of these hybrid Cbz/Pyr-monomers was highly dependent on the relative number of Cbz versus Pyr unit(s) present in corresponding monomers. Indeed, a successful electro-deposition of the corresponding conducting polymeric films onto a working Pt electrode was observed only for hybrid monomers characterised by a Cbz/Pyr unit(s) ratio greater than or equal to 1. This result has been validated by systematically tuning the number of oxidisable Cbz and Pyr unit(s) present in monomers through proper chemical design and monomer multi-step synthesis. In that case, cyclic voltammogram analyses readily confirmed the exclusive electro-deposition of conductingpolyCbz-films.     

Polycarbazole-based electrochemical transistor

A polycarbazole conducting polymer transistor has been constructed having the dimensions 1 cm × 2 cm × 1 mm. Polycarbazole film used here has a redox potential of 1.30 V. Polymer-coated platinum plates were used as the source and drain. The inter-electrode spacing of the device is typically of the order of 200–500 μm to minimise the internal resistance. The high saturation current region of the transistor in the most positive bias voltage (1.3 V), with negligible hysteresis and greater stability, appears to give a device that is superior to other conducting polymer transistors. Received: 27 May 1997 / Accepted: 17 September 1997     

四氢呋喃/三氟化硼乙醚混合电解质中咔唑的电化学聚合

在四氢呋喃/三氟化硼乙醚混合电解质中直接阳极氧化咔唑制备聚咔唑.单体的起始氧化电位为0.92 Vversus SCE,远低于单体在含0.1 mol.L-1Bu4NBF4的乙腈溶液中的起始氧化电位(1.36 Vversus SCE).在此体系中获得的聚咔唑膜具有良好的电化学活性和稳定性,其电导率为7.0×10-3S.cm-1.聚合物可部分溶解于二甲基亚砜等强极性有机溶剂.UV-Vis,FT-IR,1H-NMR证明聚合物共轭长链的形成.该体系中获得的聚咔唑是一种蓝光发射材料,并具有良好的热稳定性.     

Ionic liquid supported on an electrodeposited polycarbazole film for the headspace solid‐phase microextraction and gas chromatography determination of aromatic esters

A polycarbazole film was electrodeposited on a stainless‐steel wire from a solution of N,N‐dimethylformamide/propylene carbonate (1:9 v/v) containing 0.10 M carbazole and 0.10 M tetrabutylammonium perchlorate. The obtained polycarbazole fiber was immersed into an ionic liquid (1‐hydroxyethyl‐3‐methyl imidazolium bis[(trifluoromethyl)sulfonyl]imide) solution (in dimethylsulfoxide) for 30 min, followed by drying under an infrared lamp. The resulting polycarbazole/ionic liquid fiber was applied to the headspace solid‐phase microextraction and determination of aromatic esters by coupling with gas chromatography and flame ionization detection. Under the optimized conditions, the limits of detection were below 61 ng/L (S/N = 3) and the linear ranges were 0.061?500 μg/L with correlation coefficients above 0.9876. The relative standard deviations were below 4.8% (n = 5) for a single fiber, and below 9.9% for multi‐fiber (n = 4). This fiber also exhibited good stability. It could be used for more than 160 times of headspace solid‐phase microextraction and could withstand a high temperature up to 350°C.     

Copper(II) ion-selective microelectrochemical transistor

A device has been developed for the measurement of copper(II) ions (Cu²⁺) in aqueous medium. The device reported here is an electrochemical transistor which consists of two platinum electrodes separated by 100 μm spacing and bridged with an anodically grown film of polycarbazole. Polycarbazole film (undoped form) is observed to be highly selective for the Cu(II) ions. In a completed device, the conductivity of the polycarbazole film changes on addition of Cu(II) ions. The change in conductivity is attributed to the conformational changes in the polymer phase on occupation of the Cu(II) ions, without affecting electron/proton transfer. The device turns on by adding 2.5 × 10⁻⁶ M Cu(II) ions and reaches a saturation region beyond 10⁻⁴ M Cu(II) ion concentrations. In the above concentration range, the device response [I _D vs. log Cu(II) ion concentration] is linear. The selectivity of the device for other metal ions such as Cu(I), Ni(II), Co(II), Fe(II), Fe(III), Zn(II) and Pb(II) is also studied. Received: 6 April 1999 / Accepted: 20 August 1999     

Electrochemical fabrication of a novel polycarbazole coating for the headspace solid‐phase microextraction and GC determination of some chlorobenzenes

A novel polycarbazole coating was prepared by cyclic voltammetry on a platinum wire. The solution for electropolymerization contained N,N‐dimethylformamide, propylene carbonate (v/v = 1:9), 0.10 M carbazole and 0.10 M tetrabutylammonium perchlorate; the cyclic scan potential range was 0.8–2.0 V (versus Ag/AgCl). The resulting polycarbazole coating showed a porous structure and had a large specific surface area. When it was used for the headspace solid‐phase microextraction of chlorobenzenes (i.e. chlorobenzene, 2‐chlorotoluene, 1,2‐dichlorobenzene, 1,3‐dichlorobenzene, 1,2,4‐trichlorobenzene) followed by GC analysis, it presented excellent analytical performance. Under the optimized conditions the linear ranges were 0.25–250 μg/L with correlation coefficients >0.985, and the low detection limits were 15–61 ng/L (S/N = 3) for different chlorobenzenes. The RSDs were 2.4–4.9% for five successive measurements with a single fiber, and for fiber‐to‐fiber they were 6.3–13.1% (n = 5). Furthermore, the polycarbazole coating displayed good thermal stability (>350°C) and durability (more than 250 times). The proposed method was successfully applied to the extraction and determination of chlorobenzenes in waste water and lake water, and the recoveries for standards added were 86–114% for different analytes.     

Influence of monomer concentration on polycarbazole–polyindole (PCz–PIn) copolymer properties: Application in Schottky diode

Copolymerization of carbazole (Cz) and indole (In) is successfully performed through potentiostatic polymerization; and the influence of the monomer concentrations ratio on copolymer formation, is investigated. It is found that 1:2 ratio of Cz to In monomer is optimum for the synthesis of a copolymer with high electroactivity. The structural, optical, thermal and morphological analysis of the copolymers are carried out with UV–vis, FT–IR spectroscopy, differential scanning coulometry (DSC) and scanning electron microscopic (SEM) technique. Electrochemical and thermal studies, further support better redox activity and thermal stability of the copolymer, respectively. We also report fabrication and characterizations of the electrochemically synthesized copolymer in organic Schottky diode with configuration metal Al/copolymer/indium tin oxide coated glass (ITO). The current density–voltage (J–V) characteristic of the Schottky diode is consequential in extracting the electronic parameters and the charge transport mechanism of the devices.     

Nanocomposite of Platinum Particles Embedded into Nanosheets of Polycarbazole for Methanol Oxidation

Nanoparticles of Pt were successfully electrodeposited onto polycarbazole (PCz) film on a stainless steel (SS‐PCz‐Pt) by chronocoulometry (0.2 C). For comparative purposes, Pt particles were deposited into stainless steel (SS‐Pt) under the same condition. Fourier transform infrared spectroscopy (FT‐IR) results confirmed PCz exists in the SS‐PCz‐Pt composite electrode. X‐ray photoelectron spectroscopy (XPS) results indicated that PCz of SS‐PCz can interact easily with Pt particles. The crystalline behavior and morphology of SS‐PCz‐Pt and SS‐Pt were determined by X‐ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and Transmission Electron Microscopy (TEM). The TEM results indicated that Pt particles disperse more uniformly into the nanosheets of polycarbazole than those of SS film. Catalytic activity and stability for the oxidation of methanol were studied by using cyclic voltammetry and chronoamperometry. A high catalytic current for methanol oxidation (8.04 mA cm^?2 mg^?1) was found for the SS‐PCz‐Pt electrode in comparison to SS‐Pt electrode (5.01 mA cm^?2 mg^?1) at about 0.6 V (vs. Ag/AgCl).     

烷基步长对聚丙烯酸修饰咔唑电聚合的影响

合成了含有不同烷基链取代的N-丙烯酰氧癸基咔唑(MACZ10)和N-丙烯酰氧十二烷基咔唑(MACZ12), 通过自由基聚合得到聚N-丙烯酰氧烷基咔唑(PMACZ). 分子量分析表明, 随着烷基链长度的增加, 聚合物分子量减小, 分布变宽. 荧光光谱表明, 随着烷基链长度的增加, 聚合物在353 nm处的发射峰逐渐减弱. 在四氢呋喃和体积分数为10%三氟化硼乙醚与四氟化硼四丁基胺的混合电解质溶液中, 直接阳极氧化PMACZ获得自支撑交联网状的聚(聚N-丙烯酰氧烷基咔唑)(PPMACZ)薄膜. PPMACZ薄膜具有良好的氧化还原活性、热稳定性和蓝色发光性能, 聚合物氧化还原可逆性随着烷基链长的增加而增加, 且发射峰变宽.