Alkylated graphene nanosheet composites with polyaniline nanofibers

We demonstrate a simple method to prepare alkylated graphene/polyaniline composites (a-GR/PANI) using solution mixing of exfoliated alkyl Iodododecane treated graphene oxide sheets with polyaniline nanofiber; polyaniline nanofibers (PANI) prepared by using rapid mixing polymerization significantly improve the processibility of polyaniline and its performance in many conventional applications. Also, polyaniline nanofibers exhibit excellent water dispersibility due to their uniform nanofiber morphology. Morphological study using SEM and TEM analysis showed that the fibrous PANI in the composites a-GR/PANI mainly adsorbed onto the surface or intercalated between the graphene sheets, due especially to the good interfacial interaction between the alkylated gaphene and the polyaniline nanofibers. The existence of polyaniline nanofibers on the surface of the garphene and the alkylated graphene sheets was confirmed by using FT-IR, FT-Raman and X-ray diffraction analysis. Due to the good interfacial interaction between the alkylated graphene and the polyanilines nanofibers, the composite (a-GR/PANI) exhibited excellent dispersion stability in DMF compared to the same composite (GR/PANI) without alkylation. The electrical conductivity of the (GR/PANI) composite was 9% higher than that of pure PANI and the same weight percent for the composite after alkylation was 13% higher than that of pure PANI nanofibers.     

Nanofibrous TiO2-core/conjugated polymer-sheath composites: synthesis, structural properties and photocatalytic activity

Nanofibrous TiO2-core/conjugated polymer-sheath composite nanocables were synthesized by in-situ chemical oxidative polymerization of aniline with oxidant in the presence of TiO, nanofibers prepared through an electrospinning process. During the polymerization process, aniline molecules were adsorbed on the surface of TiO2. Upon the addition of oxidant, the polymerization of aniline takes place on the surface of the TiO2 nanofibers and polyaniline (PANI) is gradually deposited on their surface. The resulting TiO2-PANI nanocomposites have a coaxial nanocable structure. The morphological and structural properties of the composite nanocables were analyzed by using high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and UV-visible spectroscopy (UV-vis), respectively. The HRTEM images proved that PANI (20 nm thickness) covered the surface of the TiO2 nanofibers. Also, the photocatalytic activity for the degradation of organic dyes on fibrous photocatalysts under UV-light was studied. The photocatalytic experiments showed that dye could be degraded more efficiently on the TiO2-PANI composite nanocables than on pure TiO2, due to the charge transfer from PANI to TiO2. The method for the synthesis of these unique structured composite nanocables is simple, rapid and reproducible. This facile method may be developed to produce multifunctional nanocomposites of various polymers with metal oxide fibers on a large scale for various technological applications such as sensors, solar cells, and catalysts.     

Effects of synthetic conditions on the structure and electrical properties of polyaniline nanofibers

Polyaniline nanofibers were synthesized by interfacial polymerization in the presence of hydrochloric acid (HClO₄). The effects of the molar ratio of ammonium persulfate (APS) to aniline (ANI) (represented by [APS]/[ANI] ratio) and HClO₄ concentration on the morphology, chain structures, and electrical properties of the polyaniline (PANI) were investigated to understand the formation of nanofibers. The structure and properties of the resulted PANI were characterized with FTIR, UV–Vis, TEM, XRD, and conductivity in detail. The results showed that low [APS]/[ANI] ratio (≤1/4) and high HClO₄ concentration (≥1000 mol/m³) were benefit to the preparation of uniform PANI nanofibers with low content of phenazine-like units and ANI oligomers, and high conductivity.     

Synthesis of high-performance one-dimensional polyaniline nanostructures using dodecylbenzene sulfonic acid as soft template

High-performance one-dimensional polyaniline (PANI) nanostructures, i.e. nanotubes and nanofibers were synthesized in the presence of dodecylbenzene sulfonic acid (DBSA) and hydrochloric acid (HCl) aqueous solution, with ammonium peroxydisulfate (APS) as oxidant. And the resulting PANI nanotubes possessed the diameters of 350-650 nm and length up to tens of micrometers and PANI nanofibers with diameters of 120-160 nm, respectively. Especially, the PANI nanotubes had a very uniform structure (nearly 100% in nanotubes) and the reaction yield was about 110% (compared to the quantity of aniline in the reaction). The formation mechanism of 1D PANI nanostructures was also proposed. The guide effect of the initial “soft-template” formed by aniline and DBSA was greatly controlled by its content and chemical structures.     

Synthesis of highly conductive polyaniline nanofibers

Polyaniline nanofiber product synthesized by using both potassium biiodate, KH(IO₃)₂, and sodium hypochlorite oxidant shows high electrical conductivity of greater than 100 S cm^− 1. The nanofiber product also shows not only a long nano-size fibril structure with average diameter of ~ 50 nm and length of ~ 4 μm but also high crystallinity. It was observed that the nanofibers synthesized using the two oxidants give both high electrical conductivity and high crystallinity compared to polyaniline synthesized using commonly known ammonium peroxydisulfate (APS) oxidant. We also found that dimensional and morphological uniformity of PANI nanofibers were greatly improved when the two oxidants were used. The long length and high crystallinity will probably be the contributing factors to have high conductivity. Order of the oxidant addition for the synthesis has no effect on quality of the product. Characterization study was made via UV/Vis absorption spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as conductivity measurement.     

Pd/PANI纳米纤维的液相合成及其对乙醇的电化学行为

以苯胺为单体、PdCl₂为金属前驱体、过硫酸铵为氧化剂,在避光条件下液相化学氧化合成Pd/PANI纳米纤维,用XRD、FESEM、TEM、SAED、HRTEM、FT-IR和UV-vis等手段对其表征,研究了 Pd/PANI纳米纤维修饰玻碳电极对乙醇的电化学行为。结果表明,Pd/PANI纳米纤维的平均直径为20 nm,长度为500 nm;平均直径为6 nm的纳米Pd颗粒单分散分布在PANI纤维中;Pd/PANI纳米纤维修饰电极的ECSA值为54.76 m²/g_Pd,是商用Pd/C催化剂(6.08 m²/g_Pd)的9倍,其j_f/j_b值为1.192。     

Enhanced effect of dopant on polyaniline nanofiber based electrorheological response

As a potential candidate for electrorheological (ER) materials, polyaniline (PANI) nanofibers were synthesized via an interfacial polymerization route, because of their easy synthesis, high stability, controllable conductivity and good ER response. In this study, a new dopant, indole-2-carboxylic acid, was used to improve the ER performance. The synthesized PANI nanofibers were dispersed in silicone oil at 10 vol% and their rheological properties as an ER fluid were examined using a rotational rheometer under a variety of electric field strengths. In addition, their dielectric properties were studied using a LCR meter. The results showed that indole-2-carboxylic acid, which has high polarizability, enhanced the ER effect of PANI nanofibers, showing that polarizability is an important parameter affecting the ER behavior.     

High-performance asymmetric supercapacitors based on reduced graphene oxide/polyaniline composite electrodes with sandwich-like structure

The sandwich-like structure of reduced graphene oxide/polyaniline(RGO/PANI) hybrid electrode was prepared by electrochemical deposition. Both the voltage windows and electrolytes for electrochemical deposition of PANI and RGO were optimized. In the composites, PANI nanofibers were anchored on the surface of the RGO sheets, which avoids the re-stacking of neighboring sheets. The RGO/PANI composite electrode shows a high specific capacitance of 466 F/g at 2 m A/cm~2 than that of previously reported RGO/PANI composites. Asymmetric flexible supercapacitors applying RGO/PANI as positive electrode and carbon fiber cloth as negative electrode can be cycled reversibly in the high-voltage region of 0–1.6 V and displays intriguing performance with a maximum specific capacitance of 35.5 m F cm~(-2). Also, it delivers a high energy density of 45.5 m W h cm~(-2) at power density of 1250 m W cm~(-2). Furthermore, the asymmetric device exhibits an excellent long cycle life with 97.6% initial capacitance retention after 5000 cycles.Such composite electrode has a great potential for applications in flexible electronics, roll-up display,and wearable devices.     

Investigations on copper chloride doped polyaniline composites as efficient electrode materials for supercapacitor applications

In this study, we have discussed the potential of using copper chloride (CuCl₂) doped Polyaniline (PANI) as an electrode material for supercapacitor application. PANI in pure and doped forms with various doping levels of CuCl₂ (doping levels of 1, 2, 3 and 4 wt%) were synthesized by in situ polymerization method, using ammonium peroxodisulfate as oxidant in HCl medium. The morphology of the doped polymeric materials was studied by scanning electron microscope and transmission electron microscope analysis. The interaction between PANI and the metal cation (Cu²⁺) was confirmed by the fourier transform infrared spectroscopy analysis. Thermal stability of the materials was examined by thermogravimetric analysis. Electrochemical characterizations of the materials were carried out by three electrode probe method where, platinum and saturated standard calomel electrode were used as counter and reference electrode respectively. 1 M KCl solution was used as electrolyte for all the electrochemical characterizations. Among all the materials, PANI shows highest specific capacitance value at the doping level of 2 wt%.     

Free-standing TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript>/PANI composite nanofibers for ammonia sensors

Free-standing TiO₂–SiO₂/polyaniline (TS/PANI) composite nanofibers were prepared by electrospinning, in situ polymerization and calcination method. The effect of tetra-n-butyl titanate (TBT) in the electrospinning solution on the morphology and the ammonia sensing properties of TS/PANI composite nanofibers were investigated. The obtained nanofibers were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermo-gravimetric analysis and gas sensor test system. It is proved that too much TBT in the solution would make the fibrous morphology and ammonia sensing properties worse. Gas sensing tests showed that the TS/PANI composite nanofibers ammonia sensor can work at room temperature and possess ideal response values, selectivity and repeatability. With the increase in TiO₂ content in the TS nanofibers, the ammonia sensing properties were improved because of the increase in P–N heterojunctions formed between TiO₂ and PANI in the sensors.     

FeCl3/APS复合氧化剂对乳液法制备聚苯胺电化学性能及其结构的影响

首次采用三氯化铁（FeCl3）和过硫酸铵（APS）为复合氧化剂,在乳液聚合体系中制备了十二烷基苯磺酸掺杂的聚苯胺（PANI）,同时以碳纸负载PANI为工作电极,通过循环伏安（CV）和Tafel曲线测试方法,探讨了FeCl3与APS的摩尔比（n（FeCl3）/n（APS））及复合氧化剂与苯胺的摩尔比（n（compositeoxidant（cod））/n（An））对乳液法制备PANI电化学性能的影响;并通过对PANI的电导率热稳定性、X射线衍射（XRD）和热重分析（TGA）的对比分析,印证了PANI电化学性能的表征结果。实验结果表明与APS制备的PANI相比,n（FeCl3）/n（APS）=3.5∶1,n（cod）/n（An）=3∶1时,复合氧化剂制备的PANI具有更大的峰电流和更高的腐蚀电位,电导率热稳定性更佳;XRD和TGA的结果显示复合氧化剂制备的PANI具有更好的结晶性和热稳定性。     

Chemical synthesis of highly stable PVA/PANI films for supercapacitor application

Polyvinyl alcohol (PVA)/polyaniline (PANI) thin films were chemically synthesized by adopting two step process: initially a thin layer (200 nm) of PVA was spin coated by using an aqueous PVA solution onto fluorine doped tin oxide (FTO) coated glass substrate, afterwards PANI was chemically polymerized from aniline monomer and dip coated onto the precoated substrate. The thickness of PANI layer was varied from 293 nm to 2367 nm by varying deposition cycles onto the precoated PVA thin film. The resultant PVA/PANI films were characterized for their optical, morphological and electrochemical properties. The FT-IR and Raman spectra revealed characteristic features of the PANI phase. The SEM study showed porous spongy structure. Electrochemical properties were studied by electrochemical impedance measurement and cyclic voltammetry. The electrochemical performance of PVA/PANI thin films was investigated in 1 M H₂SO₄ aqueous electrolyte. The highest specific capacitance of 571 Fg⁻¹ was observed for the optimized thickness of 880 nm. The film was found to be stable for more than 20,000 cycles. The samples degraded slightly (25% decrement in specific capacitance) for the first 10,000 cycles. The degradation becomes much slower (10.8% decrement in specific capacitance) beyond 10,000 cycles. This dramatic improvement in the electrochemical stability of the PANI samples, without sacrificing specific capacitance was attributed to the optimized PVA layer.     

Comparison of the electrochemical performance of self-cross-linked and free-standing polyaniline electrodes

Cross-linked polyaniline (PANI) gel can provide rapid transfer channels for electrons and ions, and self-cross-linked PANI (SC-PANI) electrodes have been previously reported. However, there are few reports on the preparation of free-standing PANI (FS-PANI) electrodes. Hence, new preparation technologies are required for FS-PANI electrodes and their electrochemical performance must be estimated. Moreover, FS-PANI must be compared with SC-PANI to better estimate their performance. In this study, SC-PANI was prepared using p-phenylenediamine (PPD), phytic acid, aniline (An), and ammonium persulfate as the additive, doping acid, monomer, and oxidant, respectively. Then, it was hydrothermally transformed into FS-PANI. The microstructures of SC-PANI and FS-PANI were characterized using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, and their electrochemical performances were tested using cyclic voltammetry, galvanostatic charge–discharge (CD) measurement, and electrochemical impedance spectroscopy. When the molar ratio of PPD to An was 0.10, the electrochemical performance of SC-PANI was the best as it achieved the largest specific capacitance (Cs) (403 F/g) and lowest internal resistance. After 2000 CD cycles, Cs remained at 73%. However, the Cs of FS-APNI was 511 F/g and 97% of the initial Cs value was maintained after 2000 CD cycles. This study is expected to provide an effective basis for the future research on free-standing electrode materials for supercapacitors.

     

Preparation of electrospun nanofibers of star-shaped polycaprolactone and its blends with polyaniline

The electrospun nanofibers of synthetic star-shaped poly(?-caprolactone) (PCL) and its blends with polyaniline (PANI) were prepared. We utilized the advantages of star-shaped PCL and benefits of electrospinning method for obtainment of the uniform nanofibers with improved properties for tissue engineering. Biodegradable star-shaped PCL with four arms was synthesized by Sn(Oct)₂-catalyzed ring-opening polymerization (ROP) of ?-caprolactone (CL) from a pentaerythritol core. The chemical structure of star-shaped PCL was investigated by FTIR, and average molecular weight of polymer was determined by ¹HNMR (about 38000 g mol^?1). Thermal behavior of star-shaped PCL was also studied by Thermogravimetric Analysis (TGA). Moreover, the cyclic voltammetry (CV) measurement confirmed the preparation of electroactive nanofibers. The scanning electron microscopy (SEM) was also used to investigate the morphology of electrospun nanofibers produced from star-shaped PCL and its blends with PANI with different feed ratios. The presence of PANI resulted in fibers with diameters less than 100 nm and significant decrease of bead formation.     

电磁搅拌法制备导电聚苯胺纳米线的电磁屏蔽性能研究

针对低频频段(<1.5GHz)的电磁屏蔽涂层,采用快速混合法制备出导电聚苯胺纳米线,使用透射电镜(TEM)对其形貌和尺度进行表征,研究了搅拌方式对聚苯胺/聚氨酯涂层的导电性能和电磁屏蔽性能的影响。研究表明,由于磁场的作用,采用电磁搅拌法可以缩短聚苯胺聚合反应时间,合成均一的导电聚苯胺纳米线,其渗滤阈值为33.3%,含量为33.3%的聚苯胺纳米线的聚苯胺/聚氨酯涂层的电磁屏蔽性能为32.2dB,优于含量为45%的机械搅拌法制备的聚苯胺粉体,这可能是由于线性结构的导电聚苯胺在基体中能够较容易形成三维导电网络结构所致。     

A novel hierarchically carbon foam templated carbon nanotubes/polyaniline electrode for efficient electrochemical supercapacitor

In this work, a high-performance electrode material has been fabricated by the incorporation of carbon nanotubes (CNTs) and polyaniline (PANI) on a carbon foams (CF) to improve its electrochemical performance. The microstructure and performance of as-prepared material was characterized in detail. Results showed that the resultant material exhibited a high gravimetric capacitance up to 467.1?F g^?1, higher energy density of 104. 2?Wh kg^?1 and power density of 3000?W kg^?1 at a current density 3?A g^?1 when the electrochemical doping time of PANI equals to 20?min. Furthermore, it appeared a good cycling stability with capacitance retention of 94.5% after 10000 cycles. The enhanced electrochemical performance can be attributed to the unique carbon nanostructure and synergistic effects of active materials CNTs and PANI. It indicates that this novel CF/CNTs/PANI-20 composite is a promising candidate for electrochemical capacitors.     

Synthesis of oriented polyaniline flake arrays

We first report the synthesis of oriented polyaniline (PANI) flake arrays by a self-assembly method with inorganic acid as a dopant. It is found that the morphology and molecular structure depend on aniline concentration. FTIR and XRD results reveal that the oriented PANI flake arrays are in high conductive emeraldine state, which is expected to show excellent electrochemical properties. Cyclic voltammograms of I₂/I^- system measurement shows that the oriented PANI flake arrays present small charge-transfer resistance and high electrocatalytic activity. The oriented PANI flake arrays are expected to be useful in electrical, optical and electrochemical devices.     

Synthesis of polyaniline nanofibers with high electrical conductivity from CTAB–SDBS mixed surfactants

Mixed surfactant solution, containing cetyltrimethyl ammonium bromide (CTAB) and sodium dodecylbenzyl sulfonate (SDBS), is used to prepare polyaniline (PANI) with soft 1D structure and high electrical conductivity. The mixed surfactants in the reaction play double roles of soft templates and dispersion reagents. The influence of CTAB–SDBS ratio on the morphology and conductive property of PANI is investigated. Through varying the proportion of surfactants, uniformly branched nanofibers with higher aspect ratio and good dispersion are obtained, which possess the highest conductivity (0.102 S·cm^?1). Moreover, FT-IR spectra are measured to explain the change of structure and conductivity under assistance of mixed surfactants. As a result, the mixed surfactants have significant effect on the electron density of whole structure as well as the PANI molecular orientation.     

Synthesis and characterization of nanotree-like polyaniline electrode material for supercapacitors

In this work, polyamidoamine (PAMAM) dendrimers are used as templates to synthesize nanotree-like polyaniline (PANI) materials, which are further used as electrode materials for supercapacitors. Effects of PAMAM content on PANIs’ structural characteristics and electrochemical properties are investigated detailedly. SEM images show that at 0.1 % PAMAM content, the PANI presents a stable self-assembled dendritic structure composed of many nanorods. Compared with pure PANI, nanotree-like PANI has better crystallinity, higher doping degree, larger high surface area and better reactivity. At a current density of 1 A g^?1, the PANI nanotree electrode displays a high specific capacitance value of 812 F g^?1, which is 119 % higher than that of pure PANI. Even after 1000 cycles, it still maintains about 69 % of the initial capacitance, showing good electrochemical stability. Thus the PANIs with nanotree structures are promising electrode materials for high-performance electrical energy storage devices. Moreover, the possible electrochemical enhancement mechanism of PANI nanotree electrode for supercapacitor is also discussed.     

Processible polyacid doped polyaniline composites: Application for charge storage devices

Processible polyaniline (PANI) composites with a polyacid (polyacrylic acid, PAA) are synthesized and studied for their structural, electrical and electrochemical properties. The material is used for the first time for development of electrochemical capacitor. The processible conducting composites have been prepared by mixing the polyaniline and polyacrylic acid in various weight percentage from 20 wt.% to 90 wt. % (of polyaniline) under vigorous stirring and sonication conditions. Self-standing films of these electroactive and homogeneous composites were obtained by solution casting method. A significant improvement in processibility, crystallinity and stability was observed in the composites having PANI up to 90 wt.% of total content. However, the electrical conductivity decreased remarkably as the percentage of PANI decreased in the composites. The composite having 60 wt.% PANI in PAA showed very interesting structural property as it is found to be highly crystalline with orthorhombic crystal system and cell parameters as a = 5.93 Å, b = 7.57 Å and c = 10.11 Å. The composites are used for the development of electrochemical capacitors. The 60 wt.% PANI-PAA composite showed highest capacitance amongst all the composites and used as an active material for development of an electrochemical capacitor using a parallel plate assembly.