The electrocatalytic oxidation of ascorbic acid on polyaniline film synthesized in the presence of camphorsulfonic acid

Polyaniline-camphorsulfonic acid (PAN-CSA) composite film on platinum electrode surface has been synthesized via the electrochemical polymerization of aniline in the presence of camphorsulfonic acid (CSA). It was found that the doping of polyaniline (PAN) with CSA extends the electroactivity of PAN in neutral and even in alkaline media. The PAN-CSA composite film coated platinum electrodes are shown to be good electrocatalytic surfaces for the oxidation of ascorbic acid (AA) in phosphate buffer solution (PBS) of pH 7.0. The anodic peak potential of AA shifts from 0.63 V at the bare platinum electrode to 0.34 V at the PAN-CSA composite modified platinum electrode with a greatly enhanced current response. A linear calibration graph is obtained over the AA concentration range of 5-50 mM using cyclic voltammetry. The kinetics of the catalytic reaction are investigated using rotating disk electrode voltammetry and chronoamperometry. The results are explained using the theory of electrocatalytic reactions at chemically modified electrodes. The PAN-CSA composite on the electrode surface shows good reproducibility and stability.

Poly(vinylidene fluoride-hexafluoropropylene)/organo-montmorillonite clays nanocomposite lithium polymer electrolytes

Polymer-clay nanocomposite (PCN) materials were prepared by intercalation of an alkyl-ammonium ion spacing/coupling agent and a polymer between the planar layers of a swellable-layered material, such as montmorillonite (MMT). The nanocomposite lithium polymer electrolytes comprising such PCN materials and/or a dielectric solution (propylene carbonate) were prepared and discussed. The chemical composition of the nanocomposite materials was determined with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy, which revealed that the alkyl-ammonium ion successfully intercalated the layer of MMT clay, and thus copolymer poly(vinylidene fluoride-hexafluoropropylene) entered the galleries of montmorillonite clay. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical properties of the lithium polymer electrolyte. Equivalent circuits were proposed to fit the EIS data successfully, and the significant contribution from MMT was thus identified. The resulting polymer electrolytes show high ionic conductivity up to 10(-3) S cm(-1) after felling with propylene carbonate.

The morphology and thermal properties of multi-walled carbon nanotube and poly(hydroxybutyrate-co-hydroxyvalerate) composite

Nanocomposites based on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and multi-walled carbon nanotubes (MWNTs) were prepared by solution processing. Ultrasonic energy was used to uniformly disperse MWNTs in solutions and to incorporate them into composites. Microscopic observation reveals that polymer-coated MWNTs dispersed homogenously in the PHBV matrix. The thermal properties and the crystallization behavior of the composites were characterized by thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction, the nucleant effect of MWNTs on the crystallization of PHBV was confirmed, and carbon nanotubes were found to enhanced the thermal stability of PHBV in nitrogen.

New proton exchange membranes based on poly (vinyl alcohol) for DMFCs

A series of new composite proton exchange membranes for direct methanol fuel cells (DMFCs) based on poly (vinyl alcohol) (PVA), phosphotungstic acid (PWA) and silica were prepared. The highest proton conductivity (a) of these membranes is 0.017 S/cm at ambient temperature. The methanol permeability (D) of these composite membranes ranges from 10(-7) to 10(-8) cm(2)/S. From the ratios of sigma/D, it was found that the optimal weight composition of the PVA/PWA/SiO2 membrane is PVA/PWA/SiO2=0.40:0.40:0.20 wt. Infrared (IR) spectrographic measurements indicate that the Keggin structure characteristics of the PW12O403- anion is present in the composite membranes. Cyclic voltammetry shows that the electrochemical stability window of the complex membrane is from -0.5 to 1.5 V vs. Ag/AgCl electrode. The results of differential scanning calorimetry (DSC) show that silica can improve the thermal stability of the complexes and the single Tg of the membrane indicates that the membrane is homogeneous. The complexes behave as X-ray amorphous.

In situ synthesis and characterization of multiwalled carbon nanotube/Au nanoparticle composite materials

An effective and facile in Situ reduction approach for the fabrication of carbon nanotube-supported Au nanoparticle (CNT/Au NP) composite nanomaterials is demonstrated in this article. Linear polyethyleneimine (PEI) is ingeniously used as both a functionalizing agent for the multiwalled carbon nanotubes (MWNTs) and a reducing agent for the formation of An NPs. This method involves a simple mixing process followed by a mild heating process. This approach does not need the exhaustive surface oxidation process of CNTs. The coverage of Au NPs on CNTs is tunable by varying the experimental parameters, such as the initial molar ratio of PEI to HAuCl4, the relative concentration of PEI and HAUCl(4) to MWNTs, and the temperature and duration of the heat treatment. More importantly, even the heterogeneous CNT/Au composite nanowires are obtainable through this method. TEM, XPS, and XRD are all used to characterize the CNT/Au composite materials. In addition, the optical and electrocatalytic properties are investigated.

Facile preparation of amperometric laccase biosensor with multifunction based on the matrix of carbon nanotubes-chitosan composite

The carbon nanotubes-chitosan (CNTs-CS) composite provides a suitable biosensing matrix due to its good conductivity, high stability, and good biocompatibility. Enzymes can be firmly incorporated into the matrix without the aid of other cross-linking reagents. The composite is easy to form insoluble film in solution above pH 6.3. Based on this, a facilely fabricated amperometric biosensor by entrapping laccase into the CNTs-CS composite film has been developed. At pH 6.0, the fungi laccase incorporated into the composite film remains better catalytic activity than that dissolved in solution. The system is in favor of the accessibility of substrate to the active site of laccase, thus the affinity to substrates is improved greatly, such as 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS), catechol, and 0, with K. values of 19.86 mu M, 9.43 mu M, and 3.22 mM, respectively. The major advantages of the as-prepared biosensor are: detecting different substrates (ABTS, catechol, and 02), possessing high affinity and sensitivity, durable long-term stability, and facile preparation procedure. On the other hand, the system can be applied in fabrication of biofuel cells as the cathodic catalysts based on its good electrocatalysis for oxygen reduction.

A polymer composite film with reversible responsive behaviors

A responsive polymer composite film was generated by the use of reversibly switchable Surface morphology of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) films in response to different block selective solvents on the rough isotactic poly(propylene) (i-PP) substrate. The Maximum difference of the water contact angle of the composite films increased from 22.6 degrees of PS-b-PMMA films on the smooth substrate to 42.6 degrees when they were treated by PS and PMMA selective solvents, respectively. The mechanisms of the responsive extent enhanced and the superhydrophobicity of the composite films were discussed in detail.

A composite polymer film with both superhydrophobicity and superoleophilicity

A composite film composed of porous polyurethane (PU) and polystyrene (PS) microspheres with both superhydrophobicity and superoleophilicity has been prepared. In this film, the dual-scale structure enhances both the hydrophobicity and oleophilicity of the surface material. The composite film with such an 'intelligent' wettability property can be utilized to separate oil and water systems efficiently.

Preparation of core-sheath composite nanofibers by emulsion electrospinning

Uniform core-sheath nanofibers are prepared by electrospinning a water-in-oil emulsion in which the aqueous phase consists of a poly(ethylene oxide) (PEO) solution in water and the oily phase is a chloroform solution of an amphiphilic poly(ethylene glycol)-poly(L-lactic acid) (PEGPLA) diblock copolymer. The obtained fibers are composed of a PEO core and a PEG-PLA sheath with a sharp boundary in between. By adjusting the emulsion composition and the emulsification parameters, the overall fiber size and the relative diameters of the core and the sheath can be changed. A mechanism is proposed to explain the process of transformation from the emulsion to the core-sheath fibers, i.e., the stretching and evaporation induced de-emulsification. In principle, this process can be applied to other systems to prepare core-sheath fibers in place of concentric electrospinning and it is especially suitable for fabricating composite nanofibers that contain water-soluble drugs.

Preparation and properties of sulfonated poly(ether ether ketone)s (SPEEK)/polypyrrole composite membranes for direct methanol fuel cells

Polypyrrole (Ppy) was successfully introduced into methyl substituted sulfonated poly(ether ether ketone) (SPEEK) membranes by polymerization in SPEEK solutions to improve their methanol resistance. Uniform polypyrrole (Ppy) distributed composite membranes were formed by this method by the interaction between SPEEK and Ppy. The properties of the composite membranes were characterized in detail. The composite membranes show very good proton conductive capability (25 degrees C: 0.05-0.06s cm(-1)) and good methanol resistance (25 degrees C: 5.3 x 10(-7) 1.1 x 10(-6) cm(2) s(-1)). The methanol diffusion coefficients of composite membranes are much lower than that of pure SPEEK membranes (1.5 x 10(-6) cm(2) s(-1)). The composite membranes show very good potential usage in direct methanol fuel cells (DMFCs).

Electrogenerated chemiluminescence biosensor based on Ru(bpy)(3)(2+) and dehydrogenase immobilized in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bPY)(3)(2+) and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)(3)(2+) by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 x 10(-6) M for alcohol (S/N = 3) with a linear range from 2.79 x 10(-5) to 5.78 x 10(-2) M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.

Glassy carbon ceramic composite electrodes

A new carbon composite electrode material, based on dispersing glassy carbon (GC) microparticles into methyltrimethoxysilane-derived sol, is described in the present paper. The resulting glassy carbon ceramic composite electrodes (GCCEs) combine the electrochemical properties of GC with the advantages of composite electrodes, and thus offer high electrochemical reactivity, low background current and are easy to prepare, modify and renew. The new material has a low double-layer capacitance and a wide potential window. Scanning electron microscopy (SEM) images indicate significant difference in the structure of GCCE and carbon ceramic composite electrode (CCE). The electrochemical properties and advantages of GCCE should find broad utility in electroanalysis.

Composite film of carbon nanotubes and chitosan for preparation of amperometric hydrogen peroxide biosensor

A new amperometric biosensor for hydrogen peroxide was developed based on cross-linking horseradish peroxidase (HRP) by glutaraldehyde with multiwall carbon nanotubes/chitosan (MWNTs/chitosan) composite film coated on a glassy carbon electrode. MWNTs were firstly dissolved in a chitosan solution. Then the morphology of MWNTs/chitosan composite film was characterized by field-emission scanning electron microscopy. The results showed that MWNTs were well soluble in chitosan and robust films could be formed on the surface. HRP was cross-linked by glutaraldehyde with MWNTs/chitosan film to prepare a hydrogen peroxide biosensor. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for H2O2 in the absence of a mediator. The linear range of detection towards H2O2 (applied potential: -0.2 V) was from 1.67 x 10(-5) to 7.40 x 10(-4) M with correction coefficient of 0.998. The biosensor had good repeatability and stability for the determination of H2O2. There were no interferences from ascorbic acid, glucose, citrate acid and lactic acid.

Highly sensitive electrogenerated chemiluminescence produced at Ru(bpy)(3)(2+) in Eastman-AQ55D-carbon nanotube composite film electrode

The electrochemistry and electrogenerated chemilurninescence (ECL) of tris(2,2-bipyridyl)ruthenium(II) ion-exchanged in Eastman-AQ-carbon nanotube (CNT) composite films were investigated at a glassy carbon (GC) electrode. Eastman-AQ55D is a poly (ester sulfonic acid) cation exchanger available in a commercial dissolved form. It is much more hydrophilic than Nafion due to its unique structure, so Ru(bpy)(3)(2+) does not diffuse into the hydrophobic region where it may lose its electroactivity as that in Nafion. The interfused CNT could act as electronic wires that connect the electrode with Ru(bpy)(3)(2+), which made the composite film much more electronically which finally led to the increasing of Ru(bpy)(3)(2+) conductive. Besides, the negatively charged CNT could also absorb some Ru(bpy)(3)(2+). Moreover, the strong electrostatic interaction between AQ and Ru(bpy)(3)(2+) made the composite films much more stable. The combination of AQ and CNT brings excellent sensitivity with the detection limit as low as 3 x 10(-11) M for TPA.

Electropolyrnerization of polypyrrole on PFIL-PSS-modified electrodes without added support electrolytes

A novel polyelectrolyte-functionalized ionic liquid (PFIL)/poly(4-styrene sulfonate sodium) (PSS) modified electrode composed of the coaxial and coplanar working, reference and counter electrodes, was used to electropolymerize the polypyrrole. The PFIL/PSS was modified on the integrated electrode (IE) and connected by the working, reference and counter electrodes, resulting in an available charge transfer and lower Ohmic potential drop between the working and counter electrodes. Then polypyrrole (PPy) film was successfully prepared electrochemically without any participation of supporting electrolytes, only in a pyrrole monomer solution. The resulting PPy film in PFIL/PSS matrix exhibited a preferable electroactivity. Subsequently, influence of the modifications on the formation of PPy was further discussed. The results indicated that the synergetic cooperation of PFIL and PSS components accomplished such a successful electropolymerization of PPy.