A simple and an efficient strategy to synthesize multi-component nanocomposites for biosensor applications

We demonstrate that core–shell multi-component nanocomposites can be grown in situ at room temperature by a novel one-step approach without adding any reductant and stabilizer. We have presented a one-step method for the synthesis of multi-component nanocomposites in water solution, the multi-component nanocomposites could be produced directly and quickly in an in situ wet-chemical reaction. Here, Au–polypyrrole (PPy)/Prussian blue (PB) nanocomposites have been synthesized successfully under the same circumstance. With the addition of pyrrole monomers into mixture solutions, the autopolymerization of pyrrole into PPy and AuCl₄⁻ was reduced to elemental Au instantaneously as well as simultaneously. At the same time, PB produced along with elemental Au serving as a catalyst. Furthermore, we investigated the performance of Au–PPy/PB nanocomposites as amperometric sensor toward the reduction of H₂O₂, which displayed high sensitivity, fast response and good stability. The peak current of H₂O₂ increased linearly with the concentration of H₂O₂ in the range from 2.5 × 10⁻⁹ to 1.2 × 10⁻⁶ M, and the low detection limit of 8.3 × 10⁻¹⁰ M (S/N = 3) was obtained. Therefore, this work provides a new pathway to design and fabricate novel multi-component nanocomposites, which have unique characteristics and hold great applications in the fields of sensors, electrocatalysis and others.     

聚吡咯/还原氧化石墨烯复合物的合成及电容性能

通过原位聚合方法制备不同配比的聚吡咯/氧化石墨（PPy/GO）复合物,将其用NaBH4还原得到聚吡咯/还原氧化石墨烯(PPy/RGO)复合物,采用X射线衍射、红外光谱和场发射扫描电子显微镜（FESEM）对其结构和形貌进行物理表征。 采用循环伏安、恒电流充放电和交流阻抗等电化学方法系统研究了所制备样品的电化学性能。 实验结果表明,在电流密度为0.5 A/g、吡咯（Py）与GO质量比为95∶5时,得到的复合物还原前后比电容分别可达401.5和314.5 F/g,远高于单纯的GO（34.8 F/g）和PPy（267.5 F/g）。 经过1200圈循环稳定性测试后,PPy/RGO复合物比电容保持了原来的62.5%,与PPy和PPy/GO（电容保持率分别为16.8%和46.4%）相比,PPy/RGO表现出更好的循环稳定性能,有望成为超级电容器电极材料。     

Fabrication of Tiron Doped Poly-Pyrrole/Carbon Nanotubes on Low Resistance Monolayer-Modified Glassy Carbon Electrode for Selective Determination of Dopamine

In this paper, we described a novel sensor based on tiron-doped polypyrrole and carbon nanotubes (CNTs) fabricated on low resistance monolayer-modified glassy carbon electrode. First, the dodecylamine monolayer was chemically modified. Second, CNTs were controllably adsorbed onto dodecylamine. Then, tiron doped polypyrrole was electro-deposited on the CNTs film. The layer-by-layer modified electrode was sensitive to dopamine, while it made no response to even high concentration of ascorbic acid. Parameters influencing the dopamine response were optimized. High performance of the sensor was obtained, such as wide concentration range, low detection limit (3 nM), low background current, high stability, and reproducibility.     

聚吡咯-碳载Pd催化剂的制备及对甲酸的电催化氧化

通过低温氧化法在活性碳表面修饰聚吡咯(PPy-C), 并以PPy-C为载体制备了纳米Pd催化剂(Pd/PPy-C). 采用X射线衍射、扫描电镜、透射电镜等手段对载体PPy-C及催化剂Pd/PPy-C进行了表征, 电化学测试结果表明, Pd/PPy-C催化剂电极不但能够增强催化剂对甲酸催化氧化的活性, 而且还能够大幅度提高催化剂的稳定性, 因此以PPy-C为载体的Pd/PPy-C催化剂是一类具有潜在应用前景的直接甲酸燃料电池阳极催化剂. 通过分析电化学比表面随循环伏安次数的变化及多电势阶跃实验结果表明, 催化剂电极活性衰减的主要原因是载体被氧化及电极表面积累强吸附物种的结果.     

Theoretical study of sorption-induced bending of polypyrrole films

Polypyrrole films containing perchlorate were electrochemically synthesized and the bending and recovery motion of the films obtained has been investigated. It was found that the thickness of the film and ambient relative humidity (RH) were crucial to the motion of film: An increase of the film thickness decreased the displacement of the bending but increased the bending stress. On the other hand, an increase of the ambient RH decreased both functions. The motion of film was caused by the difference of expansion on both sides of the film owing to anisotropic sorption of water vapor, which could be expressed by the diffusion-limited bending model. The diffusion coefficients calculated from the bending and recovery motion at 25°C, RH 50% were 12.2 × 10⁻⁸ cm² s⁻¹ and 3.5 × 10⁻⁸ cm² s⁻¹, respectively. The maximum expansion of the film surface calculated from the bending curve was about 0.36%. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2237–2246, 1998     

Preparation and characterization of electrostrictive polyurethane films with conductive polymer electrodes

All-polymer electrostrictive soft films were developed for the first time by depositing conductive polymer (polypyrrole) directly on both sides of solution-cast electrostrictive polyurethane elastomer films. The final composite films are flexible with strong adhesion between the polyurethane film and the conductive polymer electrode. The conductivity (sheet resistivity ∼1000 Ω/□), of the polymer electrode is appropriate for its intended use. The compatible interface between the polypyrrole electrode polymer and the electrostrictive polyurethane significantly improves the acoustic and optical transparency of these composite films, compared with using a metal electrode film. The all-polymer films also exhibit comparable dielectric properties to gold-electroded polyurethane films in the temperature range from −40^°C to +80^°C. The temperature range covers the soft segment glass transition temperature of the polyurethane elastomers, which is about −20^°C. The films also show large electric field induced strain responses which are dependent on film thickness and measurement frequency. The electrostrictive characteristics in the all-polymer films show similarities to those of the films with gold electrodes under identical measurement conditions. © 1998 John Wiley & Sons, Ltd.     

A chitosan–polypyrrole magnetic nanocomposite as μ-sorbent for isolation of naproxen

An extracting medium based on chitosan–polypyrrole (CS–PPy) magnetic nanocomposite was synthesized by chemical polymerization of pyrrole at the presence of chitosan magnetic nanoparticles (CS-MNPs) for micro-solid phase extraction. In this work, magnetic nanoparticles, the modified CS-MNPs and different types of CS–PPy magnetic nanocomposites were synthesized. Extraction efficiency of the CS–PPy magnetic nanocomposite was compared with the CS-MNPs and Fe₃O₄ nanoparticles for the determination of naproxen in aqueous samples, via quantification by spectrofluorimetry. The scanning electron microscopy images obtained from all the prepared nanocomposites revealed that the CS–PPy magnetic nanocomposite possess more porous structure. Among different synthesized magnetic nanocomposites, CS–PPy magnetic nanocomposite showed a prominent efficiency. Influencing parameters on the morphology of CS–PPy magnetic nanocomposite such as weight ratio of components was also assayed. In addition, effects of different parameters influencing the extraction efficiency of naproxen including desorption solvent, desorption time, amount of sorbent, ionic strength, sample pH and extraction time were investigated and optimized. Under the optimum condition, a linear calibration curve in the range of 0.04–10 μg mL⁻¹ (R² = 0.9996) was obtained. The limits of detection (3S_b) and limits of quantification (10S_b) of the method were 0.015 and 0.04 μg mL⁻¹ (n = 3), respectively. The relative standard deviation for water sample spiked with 0.1 μg mL⁻¹ of naproxen was 3% (n = 5) and the absolute recovery was 92%. The applicability of method was extended to the determination of naproxen in tap water, human urine and plasma samples. The relative recovery percentages for these samples were in the range of 56–99%.     

Trace analysis of Pt (IV) metal ions in roadside soil and water samples by Fe3O4/graphene/polypyrrole nanocomposite as a solid-phase extraction sorbent followed by atomic absorption spectrometry

A novel Fe₃O₄/graphene/polypyrrole nanocomposite has been successfully synthesised via a simple chemical method and applied as a new magnetic solid-phase extraction (MSPE) sorbent for the separation and pre-concentration of trace amounts of Pt (IV) in environmental samples followed by flame atomic absorption spectrometric (FAAS) detection. The nanocomposite has been characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. Seven important parameters, affecting the extraction efficiency of Pt (IV), including pH, adsorption time, desorption solvent type and concentration, desorption time, elution volume and sample volume, were investigated. Under the optimised conditions, the calibration graph was linear in the range of 50–1500 μg L^?1 (R = 0.993). The detection limit and pre-concentration factor (PF) for Pt (IV) were found to be 16 μg L^?1 and 112.5, respectively. Under the optimised solid-phase extraction (SPE) conditions, the adsorption isotherm and the adsorption capacity of the nanocomposite for Pt (IV) were studied. Pt (IV) adsorption equilibrium data were fitted well to the Langmuir isotherm and the maximum adsorption capacity of the magnetic sorbent was calculated from the Langmuir isotherm model as 416.7 mg g^?1. The precision of the method was studied as intraday and interday variations. A relative standard deviation percentage (RSD%) value less than 3.0 indicates that the method is precise. Also, the accuracy of the method was tested by the analysis of the standard reference material (NIST SRM 2556) and by recovery measurements on spiked real samples. It was also shown that the optimised method was suitable for the analysis of trace amounts of Pt (IV) in roadside soil, tap water and wastewater samples.     

Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes

The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g^?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g^?1 for the CNOs/Ppy bilayer (electrochemical deposition).     

Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors

Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g^?1 at a charge/discharge rate of 1 A g^?1), good rate capability (a decay of 33 % in C_sp with charge/discharge rates increasing from 1 to 20 A g^?1), and high cycle stability (only a small decrease of 4.2 % in C_sp after 1000 cycles at a scan rate of 100 mV s^?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg^?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in C_sp after 2000 and 5000 cycles, respectively).