Electric-Field-Induced Alignment of Functionalized Carbon Nanotubes Inside Thermally Conductive Liquid Crystalline Polyimide Composite Films

The positive liquid crystals, 4′-heptyl-4-biphenylcarbonitrile (7CB), are used to functionalize carbon nanotubes (LC-CNT), which can be aligned in the liquid crystalline polyimide (LC-PI) matrix under an alternating electric field to fabricate the thermally conductive LC-CNT/LC-PI composite films. The efficient establishment of thermal conduction pathways in thermally conductive LC-CNT/LC-PI composite films with a low amount of LC-CNT is achieved through the oriented alignment of LC-CNT within the LC-PI matrix. When the mass fraction of LC-CNT is 15 wt %, the in-plane thermal conductivity coefficient (λ_∥) and the through-plane thermal conductivity coefficient (λ_⊥) of the LC-CNT/LC-PI composite films reach 4.02 W/(m ⋅ K) and 0.55 W/(m⋅K), which are 90.5 % and 71.9 % higher than those of the intrinsically thermally conductive LC-PI films respectively, also 28.8 % and 5.8 % higher than those of the CNT/LC-PI composite films respectively. Meanwhile, the thermally conductive LC-CNT/LC-PI composite films also possess excellent mechanical and heat resistance properties. The Young's modulus and the heat resistance index are 2.3 GPa and 297.7 °C, respectively, which are higher than the intrinsically thermally conductive LC-PI films and the thermally conductive CNT/LC-PI composite films under the same amount of CNT.     

Potentiometric Ag+ Sensors Based on Conducting Polymers: A Comparison between Poly(3,4‐ethylenedioxythiophene) and Polypyrrole Doped with Sulfonated Calixarenes

Potentiometric Ag⁺ sensors were prepared by galvanostatic electropolymerization of 3,4‐ethylenedioxythiophene (EDOT) and pyrrole (Py) on glassy carbon electrodes by using sulfonated calixarenes as doping ions. Poly(3,4‐ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) doped with p‐sulfonic calix[4]arene (C4S), p‐sulfonic calix[6]arene (C6S) and p‐sulfonic calix[8]arene (C8S) were compared. PEDOT and PPy doped with poly(styrene sulfonate) (PSS) were also included for comparison. The analytical performance of the conducting polymer‐based Ag⁺ sensors was studied by potentiometric measurements. All conducting polymer and dopant combinations showed sensitivity and selectivity to Ag⁺ compared to several alkali, alkaline‐earth, and transition‐metal cations. The type of the conducting polymer used for the fabrication of the electrodes was found to have a more significant effect on the selectivity of the electrodes to Ag⁺ than the ring size of the sulfonated calixarenes used as dopants. Selected conducting polymer‐based sensors were studied by cyclic voltammetry (CV) and energy dispersive analysis of X‐rays (EDAX) measurements. Results from the EDAX measurements show that both PEDOT‐ and PPy‐based membranes accumulate silver.     

Electrical and Sensing Properties of Single‐Walled Carbon Nanotubes Network: Effect of Alignment and Selective Breakdown

The electrical transport and NH₃ sensing properties of randomly oriented and aligned SWNT networks were presented and discussed. The results indicate that aligned SWNT‐FETs have better FET characteristics due to the reduced number of interconnected nodes. This was particularly true as the resistance of the devices increased. Gated electrical breakdown was implemented to selectively remove metallic (m‐) SWNTs, thereby reducing scattering centers. This technique provided significant improvements in FET characteristics resulting in greater on/off ratio (e.g. 10⁴). AC dielectrophoretic alignment followed by selective electrical breakdown of m‐SWNTs can significantly enhance the semiconducting properties of SWNT networks which resulted in highly sensitive sensors.     

Properties of Dendrimer‐Encapsulated Pt Nanoparticles Doped Polypyrrole Composite Films and Their Electrocatalytic Activity for Glucose Oxidation

A type of novel electroanalytical sensing nanobiocomposite material was prepared by electropolymerization of pyrrole containing poly(amidoamine) dendrimers‐encapsulated platinum nanoparticles (Pt‐PAMAM), and glucose oxidase (GOx). The Pt nanoparticles encapsulated in PAMAM are nearly monodisperse with an average diameter of 3 nm, and they provide electrical conductivity. Polypyrrole acts as a polymer backbone to give stable and homogeneous cast thin films, and it also defines the electrical conductivity. Both Polypyrrole and PAMAM can provide a favorable microenvironment to keep the bioactivity of enzymes such as glucose oxidase. The homogeneity of GOx/Pt‐PAMAM‐PPy nanobiocomposite films was characterized by atomic force microscopy (AFM). Amperometric biosensors fabricated with these materials were characterized electrochemically using cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and amperometric measurements in the presence of hydrogen peroxide or glucose. All those show the resultant biosensor sensitivity was strongly enhanced within the nanobiocomposite film. The optimized glucose biosensor displayed a sensitivity of 164 μA mM^?1 cm^?1, a linear range of 0.2 to 600 μM, a detection limit of 10 nM, and a response time of <3 s.     

Electrochemistry and Ion Sensing Properties of Conducting Hydrogel Layers Based on Polypyrrole and Alkoxysulfonated Poly(3,4‐ethylenedioxythiophene) (PEDOT‐S)

Acidic aqueous solutions containing pyrrole and alkoxysulfonated PEDOT derivative (PEDOT‐S) were found to undergo polymerization in the absence of an external oxidizing agent. The product was a nearly black‐colored conducting hydrogel that after separation could be dispersed in water or acetone. The suspensions could be used to deposit cast films on a polycrystalline gold electrode. The polymer modified electrode showed a nearly Nernstian potentiometric response to Ag⁺ cations in the concentration range of 10^?5–10^?1 M with the slope of 54 mV/decade. The response was specific to Ag⁺ compared to a series of alkali and transition‐metal cations (pK_Ag/M>3.7).     

聚吡咯/多壁碳纳米管及其聚氨酯导电复合材料的制备和性能

以羧基化多壁碳纳米管(MWCNTs)做模版剂,采用化学氧化法将吡咯(Py)在羧基化MWCNTs表面聚合制备PPy/MWCNTs导电材料,将其添加到溶剂型聚氨酯(PU)溶液中制备了PPy/MWCNTs/PU导电复合材料,研究了Py用量对PPy/MWCNTs及其PU复合材料性能的影响.研究表明,随Py用量的增加,PPy/MWCNTs的长度不变,管径增大,sp~2和sp~3杂化C含量先提高后减少,N的掺杂梯度降低,PPy/MWCNTs的导电率高于羧基化MWCNTs和PPy.当Py用量为羧基化MWCNTs的20%时,其导电率最大.PPy/MWCNTs中N元素的掺杂程度及其管径变化是引起PPy/MWCNTs/PU复合材料的性能不同的主要原因.增加Py用量,MWCNTs中亲水的羧基因对PPy掺杂而消耗,相同导电材料用量时纳米导电粒子数目相对减少,PPy/MWCNTs/PU复合材料的耐水性能提高,定向应力、储能模量和玻璃化温度降低,导电率先增加后减小.当Py用量为羧基化MWCNTs的15%时,导电率最大.     

Gas Sensing Ability of a Nanostructured Conducting Polypyrrole Film Prepared by Catalytic Electropolymerization on Cu/Au Interdigital Electrodes

Nanostructured conductive polypyrrole has been prepared electrochemically on the surfaces of Cu/Au interdigital electrodes in the presence of Fe(II) as catalyst and ClO₄^? as anion dopant by using constant potential amperometry and cyclic voltammetry. The morphology of the conducting films was examined by field emission scanning electron microscopy, indicating a dependence from the processing technique. The synthesized polymer was used to investigate the properties of the gas sensing ability. The effect of the catalyst concentration on the oxidation mechanism of pyrrole was discussed. The PPy‐ClO₄ gas sensors had demonstrated fast response time and high sensitivity to VOCs.     

Taurine‐Induced Fabrication of Nano‐Architectured Conducting Polypyrrole on Biomedical Titanium

In this article, taurine, one of the small biomolecules associated with bone metabolism, is firstly utilized to induce the fabrication of nano‐architectured conducting polypyrrole (NCPPy) on biomedical titanium in diverse pH values of phosphate buffer solution (PBS). Accordingly, the possible mechanism for the fabrication of NCPPy is proposed, which is dependent on the states of polytaurine from the polymerization of taurine, i.e., the inability of forming polytaurine and unordered restricted space results in taurine‐incorporated and polytaurine‐incorporated tightly packed nanoparticles (pH 6.2 and 8.0), respectively, and however, ordered restricted space constructed by polytaurine chains induces the fabrication of polytaurine‐incorporated nanopillars (pH 6.8) and polytaurine‐incorporated nanowire networks (pH 7.4).

     

The Catalytic Effect of Polypyrrole/Pt‐Cu on Oxygen Reduction Reaction

This paper studies the electrochemical properties of ppy/Pt‐Cu composite for oxygen reduction reaction (ORR) and compares it to the highly porous ppy/Pt‐Cu catalyst, which can be synthesized by galvanostatic method (ppy/Pt‐Cu(GS)). The results of the polarization, rotating disk electrode and electrochemical impedance tests are discussed to determine the electrochemical properties of the catalysts. According to the results, ppy/Pt‐Cu(GS) catalyst is more active toward ORR compared to ppy/Pt‐Cu catalyst. The rotating disk electrode data indicates four‐electron transfer mechanism for this catalyst.     

氧化石墨烯/聚吡咯插层复合材料的制备和电化学电容性能

以FeCl₃-甲基橙(MO)为模板, 通过化学原位聚合法成功制备出氧化石墨烯/聚吡咯(GO/PPy)插层复合材料. 采用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、扫描电镜(SEM)和透射电镜(TEM)等测试技术对复合材料进行物性表征. 此外, 利用循环伏安、恒电流充放电和交流阻抗测试方法对复合材料在两种不同水系电解液(1 mol·L^-1 Na₂SO₄和1 mol·L^-1 H₂SO₄)中的电化学性能进行了研究. 结果显示: 氧化石墨烯和聚吡咯表现出各自优势并发挥协同作用, 使得GO/PPy插层复合材料在中性和酸性电解液中都显示出可观的比电容. 电流密度为0.5 A·g^-1时, GO/PPy 插层复合材料在Na₂SO₄和H₂SO₄电解液中的比电容分别为449.1 和619.0 F·g^-1, 明显高于纯PPy的比电容. 经过800 次循环稳定性测试后, 两种不同电解液中, 复合材料初始容量的保持率分别为92%和62%. 其中酸性电解液体系中初始容量更大, 而中性溶液中具有更稳定的循环性能.     

Polyaniline/Single‐Walled Carbon Nanotubes Composite Based Triglyceride Biosensor

Nanocomposite film comprising of polyaniline (PANI) and single walled carbon nanotubes (SWCNT) has been fabricated onto indium‐tin‐oxide (ITO) coated glass plate using electrophoretic technique. Co‐immobilization of glycerol dehydrogenase (GDH) and lipase (LIP) has been done via N‐ethyl‐N′‐(3‐dimethylaminopropyl) carbodiimide and N‐hydroxysuccinimide chemistry to explore its application for triglyceride (tributyrin) sensing. Response studies have been done using linear sweep voltammetry revealing that LIP‐GDH/PANI‐SWCNT‐TB/ITO bioelectrode can detect tributyrin in the range of 50 to 400 mg dL^?1 with low Michaelis–Menten constant of 1.138 mM, improved response time of 12 s, high sensitivity as 4.28×10^?4 mA mg^?1 dL and storage stability of about 13 weeks.     

导电聚合物超薄膜的制备及性能表征

采用修饰LB膜法制备了导电聚合物聚-3,4-乙烯二氧噻吩/硬脂酸(PEDOT/SA)复合超薄膜. 将硬脂酸(SA)/FeCl3 LB膜暴露于EDOT单体气氛中, EDOT 单体在多层膜中聚合, 制备了PEDOT/SA多层复合LB膜. 紫外-可见光-近红外(UV-Vis-NIR)吸收光谱和X射线光电子能谱(XPS)分析表明EDOT单体在多层膜中发生聚合并生成PEDOT导电聚合物. 扫描电子显微镜(SEM)分析显示生成的PEDOT导电聚合物颗粒分散于硬脂酸LB膜中, 被LB 膜所包裹. 二次离子质谱(SIMS)及XPS分析还发现S元素含量随LB 膜的深度变化而变化, 表明PEDOT 较好地分散于多层膜中. 采用四探针电导率仪对复合多层膜的电导率进行了测试, 结果显示60 层复合LB 膜的电导率为2.6 S·cm-1, 比普通PEDOT薄膜的电导率高一个数量级, 且表现出较好的掺杂/脱掺杂能力. 研究还发现复合膜电导率与薄膜在EDOT 单体中处理时间有关, 处理时间至120 min 后电导率达到最大值并趋于稳定, 氧化剂浓度较低可能影响EDOT在LB膜中的聚合反应速率. 对复合LB 膜的气敏特性进行了分析, 发现在较低气体浓度范围(φ<30×10^-6), PEDOT 复合LB 膜有较快的反应速率, 气敏性与气体浓度呈非线性. 在较高浓度范围(φ=(30-120)×10^-6), 气敏性与浓度呈较好的线性关系. PEDOT复合LB膜对HCl气体表现出较好的响应恢复特性. 同时对PEDOT 复合膜相关的导电机理及气体敏感机理进行了分析.     

Sensitivity and Selectivity of Polypyrrole Based AC‐Amperometric Sensors for Electroinactive Ions – Frequency and Applied Potential Influence

Oxidation/reduction of polypyrrole films coupled with ion exchange on the polymer/solution interface can be utilized for amperometric sensing of electroinactive ions. Anion or cation exchanging films (polypyrrole doped by chloride or poly(4‐styrenesulfonate) ions, respectively) can be used to determine common anions (as Cl^?, NO , SO etc) or cations (K⁺, Na⁺, Li⁺, Ca²⁺, Mg²⁺) under conditions of alternating current (AC) amperometry in the range 10^?4–1 M. A sensitivity can be tuned by choosing appropriate electrode potential, corresponding to polypyrrole oxidation (anion‐exchanging films) or reduction (cation‐exchangers). Electrochemical impedance spectroscopy and AC‐voltammetry studies have shown that applied frequency and potential could also affect the observed dependence of the signal (admittance or AC‐current) on ion concentration. For high frequency the sensitivity is higher but selectivity lower, due to influence of solution conductivity on the response. For low frequencies the sensitivity is lower; however, a selectivity increase was observed due to diverse mobility of ions in the polymer film. Selectivity of AC‐amperometric responses was studied both in separate and mixed solutions.     

Electrocatalytic Reduction of Oxygen at Anthraquinonedisulfonate/Polypyrrole Composite Film Modified Electrodes and Its Application to the Electrochemical Oxidation of Azo Dye

We report here the electrocatalytic reduction of oxygen on thin anthraquindisulfonate (AQDS)/poplypyrrole (PPy) composite film modified electrodes and its application to the electrooxidation of azo dye‐amaranth. The polymer‐coated cathode exhibited good electrocatalytic activity towards oxygen reduction reaction (ORR), and allowed the formation of strong oxidant hydroxyl radical (^.OH) in the medium via Electro‐Fenton's reaction between cathodically generated H₂O₂ and added or regenerated Fe²⁺. The electrochemical behaviors of ORR in various pH solutions were described using cyclic voltammetry (CV), rotating disk electrode (RDE) and chronoamperometric (CA) techniques. The effect of solution pH on amaranth mineralization by the Fe²⁺/H₂O₂ and Fe³⁺/H₂O₂ electrooxidation systems was studied. In addition, the long‐term electrocatalytic activity and stability of the AQDS/PPy composite film during multiple experimental runs were also examined electrochemically.     

聚吡咯/聚苯胺复合型导电聚合物防腐蚀性能

采用循环伏安法,在含吡咯和苯胺的0.3 mol/L草酸水溶液中制备了聚吡咯/聚苯胺(PPy/Pani)的复合型导电聚合膜。采用红外光谱、极化曲线、自腐蚀电位-时间曲线、扫描电子显微镜和电化学阻抗谱研究了共聚膜的防腐蚀性能。结果表明,在1 mol/L H2SO4中,PPy、Pani与不锈钢基体发生氧化还原反应,促进不锈钢表面发生钝化;当苯胺与吡咯浓度比为1∶3时,制备得到的复合型导电聚合膜所保护的不锈钢自腐蚀电流最小,自腐蚀电位最高,保护时间最长。PPy、Pani及其共聚膜在3.5%NaCl溶液中电化学阻抗谱表明,所制备的PPy、Pani及其共聚物膜与不锈钢基体发生氧化还原反应,使其表面钝化;当Cl-到达不锈钢表面时,破坏钝化膜导致不锈钢腐蚀。     

聚苯胺/聚吡咯-纳米二氧化硅复合薄膜的合成及防腐性能

采用循环伏安法(CV)在316不锈钢(316SS)表面聚合生成聚苯胺/聚吡咯-纳米二氧化硅(PAni/PPySiO_2)共聚复合薄膜.通过电化学工作站、傅里叶变换红外光谱仪(FTIR)、X射线光电子能谱仪(XPS)和扫描电子显微镜(SEM)等考察了聚苯胺(PAni)、聚苯胺/聚吡咯(PAni/PPy)与PAni/PPy-SiO_2薄膜的电化学聚合过程、分子结构和特征形貌;在3.5%(质量分数)Na Cl水溶液中利用Tafel极化曲线和电化学阻抗谱(EIS)分别考察了PAni,PAni/PPy与PAni/PPy-SiO_2薄膜对不锈钢的防腐性能.结果表明,通过电化学法可以在316不锈钢表面生成PAni/PPy-SiO_2共聚复合薄膜;相对于PAni薄膜与PAni/PPy薄膜,PAni/PPy-SiO_2薄膜有着更密实的表面结构,其对不锈钢的保护能力优于PAni/PPy薄膜和PAni薄膜,纳米SiO_2的掺杂通过加强膜层的机械屏蔽作用并抑制腐蚀反应过程中电荷的传递,提高了薄膜的防腐能力.     

多次聚合法制备多孔聚吡咯厚膜及其电化学容量性能

为了得到高面积比容量的聚吡咯(PPy)膜超级电容器电极材料, 用多次聚合法合成了PPy厚膜, 聚合电量分别为8、10和12 mAh·cm-2, 掺杂离子分别为氯离子和对甲基苯磺酸根离子(TOS-). PPy膜的电化学性能采用恒电流充放电、循环伏安(CV)和电化学阻抗谱(EIS)等方法测试. 研究表明, 多次聚合法可以制备表面平整且内部均匀多孔的PPy厚膜. 在聚合电量为12 mAh·cm-2时, 用Cl-、TOS-两种离子掺杂的PPy厚膜的面积比容量高达5 F·cm-2, 并表现出理想的电化学容量性能. 同时PPy-Cl厚膜的质量比容量达到330 F·g-1, PPy-TOS厚膜的质量比容量略低(191 F·g-1), 但具有更快的充放电速率. 与一次聚合法合成的PPy 薄膜相比, 多次聚合法合成的PPy厚膜的质量比容量没有降低. 通过场发射扫描电镜(SEM)观察了一次聚合法和多次聚合法制备的PPy厚膜的截面形貌, 并讨论了多次聚合法的合成机理.     

氧化剂对PAn/PTFE复合导电膜结构和性能影响的研究

分别以过硫酸铵和正钒酸钠作氧化剂,应用膜相渗透原位化学聚合法制备聚苯胺(PAn)/聚四氟乙烯(PTFE)复合导电膜,比较考察了两种氧化剂条件下膜孔中苯胺的聚合生长行为.扫描电镜、孔径分布及电化学测试结果表明:选用两种氧化剂分别制备的复合膜,均具有较小的膜孔径;与过硫酸铵相比,使用正钒酸钠作氧化剂时,复合膜的结构更为致密,且在保持较高表面电导率(2.62S·cm-1)的同时,断面电导率提高了1～2个数量级,电化学活性增强.     

聚合物网络分散液晶复合膜的制备与性能研究

报道了一种新型树脂基的聚合物网络分散晶复合膜材料。研究了基体材料的组成，液晶种类，液晶含量，聚合温度，紫外光强度及聚合时间等聚合物网络分散液晶复合膜性能的影响。扫描电子显微镜观测，发现这种材料是由两个连相互穿构成了属于聚合物球型。     

聚吡咯/纳米SiO_2复合材料的制备及氧化性能

采用化学氧化法制备聚吡咯/纳米Si O2(PPy/n Si O2)复合材料,通过扫描电子显微镜和红外光谱对其进行表征,并将其应用到对苯二酚的氧化反应中.结果表明,PPy/n Si O2复合材料中,PPy较均匀地负载在纳米Si O2表面.在弱酸性介质中,PPy/n Si O2对对苯二酚具有很好的氧化性能.反应2 h内,对苯二酚的氧化过程符合表观一级反应动力学.结合紫外-可见光谱法分析表明,聚吡咯通过与对苯二酚之间的氢键相互作用形成聚吡咯活性中间体,将对苯二酚氧化为对苯醌,聚吡咯具有氧化剂和催化剂的双重功能.