Poly(pyrroles) containing chiral side chains: effect of substituents on the chiral recognition in the doped as well as in the undoped state of the polymer film

The chiral discrimination of different poly(pyrroles) grafted by chiral side chains was investigated both in the doped and undoped state of the polymer films. To verify the enantioselective properties in the doped state, cyclic voltammograms were recorded in acetonitrile in the presence of the enantiomers of camphorsulfonic acid and the potentiodynamic polymerization of the appropriate monomers was performed using the same chiral electrolytes. The enantiomericrecognition in the undoped state was investigated by the application of these modified electrode surfaces in the enantioselective electroreduction of the prochiral ketones 4-methyl benzophenone and 2,5-dimethyl benzophenone. One polymer exhibits a recognition ability in the doped state; the investigation for the undoped state is in progress. A second polymer does not show enantioselective properties either in the doped nor in the undoped state. Electronic Publication     

ZnS∶Co半导体量子点的制备及其光电化学性质

采用低温水热技术,分别以柠檬酸(CA)和巯基丙酸(MPA)为稳定剂,在70℃的水相中合成了单分散的,粒子尺寸约为4 nm的ZnS∶Co半导体量子点.研究了稳定剂、Co2+掺杂剂及其掺杂量对掺杂量子点发光性能和结构的影响.XRD结果表明,Co2+离子主要掺杂在量子点表面,对主体ZnS晶格没有影响.当采用MPA为稳定剂,掺杂量为5%(摩尔分数)时,掺杂量子点的荧光发射强度最高;而同样掺杂量下采用CA为稳定剂时,量子点的荧光发射强度有所下降.循环伏安研究显示,与空白ZnS量子点相比,Co2+离子的掺杂在ZnS的禁带中形成杂质能级,相应地,ZnS∶Co量子点的吸收边发生红移.与未掺杂ZnS量子点相比,掺杂量子点具有较少的表面非辐射复合中心,因而荧光发射强度显著提高.     

Spectroelectrochemical study of poly-3,4-ethylenedioxythiophene films in the presence of different supporting electrolytes

Steady-state absorption spectra of poly-3,4-ethylenedioxythiophene (PEDOT) films at different oxidation degrees and their differential cyclic voltabsorptograms are studied in 0.1 M LiClO₄, Bu₄NBF₄, and Bu₄NPF₆ solutions in acetonitrile. Three major absorption bands are obtained in the film electronic spectra: a complex band with a pronounced maximum at λ = 600 nm that corresponds to π → π* electronic transitions in reduced fragments of a PEDOT film and two absorption bands (at λ_max = 850 nm and λ_max > 1100 nm) corresponding to two oxidized film fragments. It is shown that the position and shape of absorption bands are practically independent of the nature of dopant anions, which points to the absence of pronounced interactions with positively charged polymer fragments. An attempt is made to analyze the obtained spectroelectrochemical data qualitatively to estimate the extinction coefficients and concentrations of absorbing particles and their variation in the course of redox processes.     

Fe-N/C-TsOH催化剂应用碱性介质催化氧还原的电催化活性

通过溶剂分散热处理方法制备了一种吡咯和对甲苯磺酸(TsOH)共同修饰的碳载非贵金属复合催化剂(Fe-N/C-TsOH),并采用扫描电子显微镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)对催化剂的形貌和组成成分进行表征. 借助循环伏安法(CV)和旋转圆盘技术研究了TsOH对催化剂在0.1 mol·L^-1 KOH介质中催化氧还原性能的影响. 结果表明：TsOH的存在对催化剂催化氧还原反应(ORR)的活性影响很大. 以其制备的气体扩散电极在碱性电解质溶液中催化氧还原过程时转移的电子数为3.899,远比不含TsOH修饰的催化剂催化氧还原的电子数(3.098)高. 此外,研究发现600 ℃热处理过的Fe-N/C-TsOH催化剂表现出最佳的氧还原催化性能. 相比未经热处理过的Fe-N/C-TsOH催化剂,起峰电位和-1.5 mA·cm^-2电流密度对应的电压分别向正方向移动30 和170 mV. XPS研究结果表明吡咯氮是催化剂主要活性中心,提供氧还原活性位,而TsOH加入形成的C―S_n―C和―SO_n―有利于催化剂催化氧还原活性的提高,从而使该催化剂对氧还原表现出很好的电催化性能和选择性.     

Synthesis of alkyl and N-alkyl-substituted polyanilines: A study on their spectral properties and thermal stability

Polyaniline (PANI), N-methyl- and N-ethyl-PANI, 2- and 3-ethyl-PANI as well as 2,6-dimethyl- and 3,5-dimethyl-PANI have been synthesized using ammonium persulfate as catalyst. These polymers have been studied in the undoped and doped state by FT-IR and electronic spectroscopy in the range from the UV-VIS to the NIR portion of the spectrum. As doping agent camphorsulfonic acid was used. The chemical structures of the N-methyl- and N-ethyl-PANI have been found to contain quinoneimine units along the polymer chain. In the doped state the N-alkyl-PANIs show the polaronic band transition in the NIR part of the spectrum, at longer wavelength than doped unsubstituted PANI. A similar but less pronounced phenomenon is observed in the case of ethyl-substituted phenyl rings of PANI. Dimethyl-substitution at the phenyl ring of PANI hinders the formation of high molecular weight polymer. Only oligomers are formed.The thermal stability of unsubstituted PANI in the undoped state is very high and N-alkyl substitution and phenyl ring substitution lowers the thermal stability of PANI. Doped samples show a significantly worse thermal resistance in comparison to the corresponding undoped samples, this is due essentially to the volatility and the decomposition of the protonic acid used as dopant. Good general agreement has been found between the predicted thermal stability on the basis of increment groups calculations and the experimental results.The thermal decomposition of unsubstituted and undoped PANI has been followed by FT-IR spectroscopy.     

Vibration and X-ray photoelectron spectroscopies of FeCl3-doped poly(p-diethynylbenzene)

The doping mechanism of poly(p-diethynylbenzene), chemically doped with FeCl₃, was investigated. Absorption, infrared, far infrared, Raman, X-ray photoelectron spectroscopies were used to determine the nature of the dopant in doped polymer. The experimental results suggest that the charge transfer reaction between the polymer chain and the dopant results in the formation of FeCl₄⁻ species, the π electron charge delocalization along the polymeric chain and the reduction of π-π^* transition energy.     

低温合成樟脑磺酸掺杂聚苯胺微管的电化学电容行为

在低温条件下合成了长约为2-3 μm, 外径约为300-400 nm 的樟脑磺酸掺杂聚苯胺微管. 扫描电镜(SEM)和透射电镜(TEM)显示, 生成的聚苯胺微管管径受樟脑磺酸浓度的影响, 高浓度的掺杂剂有利于管状聚苯胺的形成. 采用交流阻抗、循环伏安、恒流充放电等测试技术对不同产物的电化学电容行为进行了研究, 结果表明, 苯胺单体与樟脑磺酸的摩尔比为1:1时所得掺杂态聚苯胺电极具有较好的循环稳定性, 单电极比电容达到522 F·g-1.     

Electron absorption spectra and voltabsorptograms of poly-3-octylthiophene films

Steady-state absorption spectra of poly-3-octylthiophene films in different oxidation states and differential cyclic voltabsorptograms of poly-3-octylthiophene films in 0.1 M LiClO₄ solutions in acetonitrile are studied. Electron spectra of films demonstrate the following three absorption bands: a complex band with a pronounced maximum at λ = 450 nm, which corresponds to π → π* electron transitions in the reduced fragments of poly-3-octylthiophene films and two absorption bands (at λ_max = 780 and λ_max > 1100 nm), which correspond to the oxidized film fragments. It is concluded that two chemically and optically distinguishable oxidation products are formed during the polymer oxidation.     

溶胶-凝胶法合成Li1-xNaxMn2O4及其作为水系锂离子电池正极材料的电化学性能

用溶胶凝胶法合成了Na⁺离子掺杂的Li_1-xNa_xMn₂O₄(x=0,0.01,0.03,0.05)。X射线衍射图表明Na⁺取代Li⁺进入Li_1-xNa_x Mn₂O₄晶格中,扫描电镜图看出产物是粒径为100~300 nm的颗粒。恒流充放电测试结果表明,Li_0.97Na_0.03Mn₂O₄在2C倍率下循环100圈后放电容量保持率比未掺杂的LiMn₂O₄从51.2%提升到84.1%。循环伏安测试表明Na⁺离子掺杂降低了材料极化且增大了锂离子扩散系数。10C倍率下Li_0.97Na_0.03Mn₂O₄仍有79.0 mAh·g^-1的放电容量,高于未掺杂样品的52.1 mAh·g^-1。Na⁺离子掺杂可以稳定材料结构并提高锂离子扩散系数,从而提高LiMn₂O₄的电化学性能,是一种可行的改性方法。     

溶胶-凝胶法合成Li_(1-x)Na_xMn_2O_4及其作为水系锂离子电池正极材料的电化学性能

用溶胶凝胶法合成了Na+离子掺杂的Li_(1-x)Na_xMn_2O_4(x=0,0.01,0.03,0.05)。X射线衍射图表明Na+取代Li+进入Li_(1-x)Na_xMn_2O_4晶格中,扫描电镜图看出产物是粒径为100~300 nm的颗粒。恒流充放电测试结果表明,Li_(0.97)Na_(0.03)Mn_2O_4在2C倍率下循环100圈后放电容量保持率比未掺杂的LiMn_2O_4从51.2%提升到84.1%。循环伏安测试表明Na+离子掺杂降低了材料极化且增大了锂离子扩散系数。10C倍率下Li0.97Na0.03Mn2O4仍有79.0 m Ah·g-1的放电容量,高于未掺杂样品的52.1 m Ah·g~(-1)。Na+离子掺杂可以稳定材料结构并提高锂离子扩散系数,从而提高LiMn_2O_4的电化学性能,是一种可行的改性方法。     

钯纳米粒子修饰的三甲氧苄啶分子印迹膜传感器的制备及其识别性能研究

采用N,N′-亚甲基双丙烯酰胺(MBA)为功能单体、钯纳米粒子为掺杂剂、马来松香丙烯酸乙二醇酯为交联剂,在玻碳电极上热聚合具有三甲氧苄啶(TMP)识别性能的钯纳米材料修饰的分子印迹传感膜.采用扫描电镜及红外光谱对合成的钯纳米材料、印迹传感膜的形貌及其结构进行了表征;采用循环伏安法(CV)、交流阻抗法(EIS)对钯纳米粒子掺杂的印迹电极与无掺杂电极的电化学性能进行了研究.结果表明,纳米粒子掺杂的印迹电极与无掺杂电极的表面形貌及电化学性能明显不同.差分脉冲伏安法(DPV)表征结果表明,TMP的浓度在5.0×10-7~4.0 ×10-3 mol/L范围内与脉冲峰电流呈良好的线性关系(R=0.9995),检出限为3.2×10-8 mol/L (S/N=3).此钯纳米粒子掺杂的印迹传感器具有较高的灵敏度.即时电流测定结果表明,新诺明(SMZ)、磺胺嘧啶(SDZ)、葡萄糖 (Glu)、尿素 (Urea)对三甲氧苄啶(TMP)的测定不产生干扰.将此印迹传感器用于实际样品中TMP的检测,加标回收率为96.8%~102.0%.     

Low energy ion implantation in polybithiophene: microstructuring and microanalysis

Low energy ion implantation in polybithiophene (thickness 200 nm) forms a 20 nm thin modified surface layer. Combining surface analysis and electrochemical methods a non destructive depth resolved investigation of the properties of the implanted layer was performed. The composition of the modified layer is dependent on the implanted species: N causes doping, O has a sputtering effect. The modified layer acts as an electronic and ionic barrier as shown by cyclic voltammetry and electron transfer reactions. The effectivity of barrier formation is dependent on the sample pretreatment and the redox state. For reduced samples the redox charge increases for repeated voltammograms (regeneration effect). The according dose dependent band scheme shows an increasing surface resistivity for low doses. At high doses the surface resistivity decreases again due to graphitization. By application of a microstructured mask the polybithiophene was structured within a m range. Laterally high resolving methods revealed sharp interfaces between implanted and pristine surface ranges. The doping pattern and the electronic properties are localized and do not alter even in an electrolyte. So conducting polymers can be microstructured to give stable structures with changed composition and modified electronic and ionic properties as required for microtechnological applications.     

Low energy ion implantation in polybithiophene: microstructuring and microanalysis

Low energy ion implantation in polybithiophene (thickness 200 nm) forms a 20 nm thin modified surface layer. Combining surface analysis and electrochemical methods a non destructive depth resolved investigation of the properties of the implanted layer was performed. The composition of the modified layer is dependent on the implanted species: N causes doping, O has a sputtering effect. The modified layer acts as an electronic and ionic barrier as shown by cyclic voltammetry and electron transfer reactions. The effectivity of barrier formation is dependent on the sample pretreatment and the redox state. For reduced samples the redox charge increases for repeated voltammograms (regeneration effect). The according dose dependent band scheme shows an increasing surface resistivity for low doses. At high doses the surface resistivity decreases again due to graphitization. By application of a microstructured mask the polybithiophene was structured within a microm range. Laterally high resolving methods revealed sharp interfaces between implanted and pristine surface ranges. The doping pattern and the electronic properties are localized and do not alter even in an electrolyte. So conducting polymers can be microstructured to give stable structures with changed composition and modified electronic and ionic properties as required for microtechnological applications.     

Fluoride Substitution on Polypyrrole during Electrochemical Synthesis in the Presence of N(Bu)4BF4

Strong evidence of fluoride substitution on the pyrrole ring during electrolysis has been observed in a systematic structural and thermal analyses of polypyrrole doped with BF₄^– by direct insertion probe-mass spectrometry. To get a better understanding, not only polypyrrole samples doped with different dopant levels but also dedoped polypyrrole samples, mechanical mixtures of undoped polypyrrole and N(Bu)₄BF₄ were analyzed using pyrolysis mass and FTIR spectroscopy techniques.     

Synthesis by UV-curing and characterisation of polyurethane acrylate-lithium salts-based polymer electrolytes in lithium batteries

UV-cured caprolactone-based polyurethane acrylate (PUA) polymer blend electrolytes were prepared and characterised. To develop polymer electrolytes suited to ambient temperature, an ionically-conductive and reliable polymer electrolyte based on urethane acrylate resins synthesised from a fluorine-containing di-functional oligomer 6F ethoxylated diacrylate, a di-functional reactive diluent 1,6-hexanediol diacrylate for adjusting the viscosity, and a radical photo-initiator doped with a mixture of lithium salts were used. Free-standing flexible electrolyte films were prepared by UV-curing via free-radical photopolymerisation. The performance of the lithium polymer cell system (Li/PE(F4)/LiCoO₂) was determined by electrochemical impedance spectroscopy, cyclic voltammetry, a galvanostatic recurrent differential pulse, chronocoulometry and chronoamperometry. The electrolyte with optimal amounts of fluorine-containing oligomer and optimal salt mixture content exhibited enhanced conductivity, showing a conductivity of 1.00 × 10^?4 S cm^?1 at ambient temperature. The specific capacity, specific energy and specific power of a Li/PE(F4)/LiCoO₂ cell were also determined.     

S-, N- and C-doped titanium dioxide nanoparticles: Synthesis, characterization and redox charge transfer study

Herein we report on the synthesis and characterization of TiO₂ nanomaterials doped with anions like sulfur, carbon and nitrogen. Upon doping, the absorption extends well into the visible region. This shift in the absorption edge is accompanied by a concomitant narrowing of band gap. The resulting anion-doped TiO₂ nanomaterials were characterized by XRD, XPS, elemental analysis, EDAX, TEM, UV-DRS, DC conductivity, AC impedance and cyclic voltammetric studies. XPS confirms the presence of the dopants and the elemental analysis determined the amount of dopants in TiO₂. Electrochemical characterization was carried out by cyclic voltammetry at pHs 2, 6.5 and 10. As against the response of undoped TiO₂, the doped samples show an active electrochemical response indicating an induced charge transfer across the titania/solution interface, thus forming two anodic peaks and a cathodic peak. This interesting and significant observation was understood in terms of band bending due to anion doping as well as to the pH changes in the experimental solutions.     

Studies on Synthesis and Effect of Dopants on Conductivity and Morphology of Organically Soluble Poly(o-anisidine)

Synthesis of poly(o-anisidine) doped with various protonic acids by using ammonium persulphate as oxidizing agent were carried out in aqueous acid media. Influences of protonic acids on the physicochemical properties were investigated. The various process parameters were optimized to obtain poly(o-anisidine) in the conducting salt phase form. The results are discussed with references to different protonic acids. It was observed that poly(o-anisidine) is highly soluble in organic solvents, such as m-cresol and N-methyl pyrrolidinone (NMP). The polymers were characterized by UV-Visible, FTIR, SEM, XRD and conductivity measurements. A result shows that, different types of dopant acids HCl, H₂SO₄ and HClO₄ affect the morphology and electrical conductivity of the polymer. The electrical conductivity of the polymer follows the order HCl >H₂SO₄>HClO₄. Thus the effect of dopant ion type and the size of its negative ions influence the physico-chemical properties. UV-Vis absorption spectra shows peaks at 740–783 nm with shoulder at 380–420 nm as characteristic peaks for the emeraldine salt (ES) phase of poly(o-anisidine) POA. The FTIR spectra show a broad and intense band at ～2800–3001 cm^?1 and ～1159–1170 cm^?1 that account for the formation of ES phase of the polymer. The X-ray diffraction spectra show a characteristic peak at 20–30^o, 2θ range which reveals partial crystalline structure. The conductivity of the poly(o-anisidne) salt was found to be in the range of 10^?3 to 10^?2 S/cm. SEM studies of poly(o-anisidine) doped with HCl shows the continuous granular uniform morphology with sub-micrometer evenly distributed particles of size ～100–200 nm.     

纳米结构Ce掺杂PbO2膜电极的电化学沉积和性质

The effect of Ce(Ⅲ) on the morphology and structure of deposited film of lead dioxide was studied by cyclic voltammetry (CV), X-ray diffractometry (XRD) and scanning tunneling microscopy (STM). The results indicated that the Ce-doped PbO2 film consisted of a mixture of α- and β-phase of PbO2. Ce doping changed the size of PbO2 crystal grains and made the crystallite size on the electrode surface in the nanometer range. Owing to the formation of nanometer-structured grains, the specific surface areas and activity sites of the electrode surface were increased, hence the catalytic activity of Ce-doped PbO2 electrode was evidently higher than that of undoped PbO2 electrode.     

Electrooptical and electrochemical properties of an ionic conjugated polymer,poly(2-ethynylpyridinum-N-benzoylsulfonate)

The electrooptical and electrochemical properties of a self-dopable ionic conjugated polyacetylene, poly(2-ethynylpyridinium-N-benzoylsulfonate) (PEPBS), were studied. The photoluminescence spectra of the polymer showed that the photoluminescence peak was located at 545 nm corresponding to the photon energy of 2.27 eV. The cyclic voltammograms of the polymer exhibited reversible electrochemical behaviors between the doped and undoped peaks. It was found from the dependence of the oxidation current density of the polymer on scan rate that the kinetics of the redox process was diffusion-controlled. The electrical conductivity (σ) of undoped PEPBS was 5.7 × 10⁻⁹ S/cm. The text was submitted by the authors in English.     

Poly(3,4-ethylenedioxythiophene) Heterogeneity: A Differential Cyclic Voltabsorptometry Study

A voltabsorptometry study of the redox behavior of poly(3,4-ethylenedioxythiophene) films in tetrabutylammonium tetrafluoroborate solutions in acetonitrile shows the polymer to exhibit heterogeneous properties when both reduced and oxidized. The measurements are taken at characteristic wavelengths selected on the basis of stationary absorption spectra. The reduced polymer's heterogeneity is explained under the assumption that the polymer contains simultaneously linear ( = 530 nm) and spiral ( = 660 nm) structures. The formation of two oxidized polymer states is proved experimentally. Both states presumably result from strong ( = 880 nm) and weak ( = 1050 nm) interactions between the anion and the positively charged polymer chain. The oxidized 880-nm state is shown to arise from the 660-nm state, whereas the 1050-nm state forms of the 530-nm state.