Facile Synthesis of Polyaniline‐Polypyrrole Nanofibers for Application in Chemical Deposition of Metal Nanoparticles

Polyaniline‐polypyrrole (PANI‐PPy) nanofibers with high aspect ratios have been synthesized by a one‐step, surfactant‐assisted chemical oxidative polymerization from mixtures of aniline (An) and pyrrole (Py) monomers. PANI‐PPy nanofibers synthesized with an excess of either PANI or PPy show similar spectral (UV‐vis and FT‐IR) characteristics as the individual homopolymers, whereas nanofibers from an equimolar mixture of An and Py display unique spectral characteristics. PANI‐PPy nanofibers undergo a spontaneous redox reaction with metal ions to produce metal nanoparticles with various morphologies and/or sizes. These findings may open new opportunities for synthesizing functional polymer nanofibers and metal nanoparticles with controllable sizes and/or morphologies.

     

Fabrication of Highly Photoluminescent TiO2/PPV Hybrid Nanoparticle‐Polymer Fibers by Electrospinning

In this study, we have synthesized highly photoluminescent TiO₂/poly (phenylene vinylene) (PPV) hybrid nanoparticle‐polymer fibers by electrospinning a PPV precursor added to a TiO₂ sol‐gel solution. The diameters of the hybrid fibers ranged from 100–300 nm and the average size of TiO₂ nanoparticles within the fibers was 10–60 nm. FT‐IR analysis indicated that a new band around 1 632 cm⁻¹ assigned to the Ti O C vibration appeared, which resulted in the stronger luminance of the fluorescence of the TiO₂/PPV hybrid fibers compared to free standing PPV nanofibers.

     

Chemical Dual‐Responsive Wettability of Superhydrophobic PANI‐PAN Coaxial Nanofibers

PANI‐PAN coaxial nanofibers have been prepared by electro‐spinning during polymerization. The surface of the resulting nanofibers is superhydrophobic with a water contact angle up to 164.5°. Conductivity of the PANI‐PAN nanofibers is about 4.3 × 10⁻² S · cm⁻¹. The superhydrophobic nanofibers show a chemical dual‐responsive surface wettability, which can be easily triggered by changing pH value or redox properties of the solution. A reversible conversion between superhydrophobicity and superhydrophilicity can be performed in a short time. The strategy used here may provide an easy method to control the wettability of smart surfaces by using properties of low‐cost functional polymers.

     

Fabrication of Self‐Assembled PEDOT/PSS‐ZnO Nanocables with Diverse Inner Core Sizes Facilitated by Vacuum Conditions

Summary: In this paper, PEDOT/PSS‐ZnO coaxial nanocables with diverse inner core sizes are prepared by a new and facile method that involves two‐steps: the synthesis of ZnO nanoparticles through a sol‐gel process, followed by dewetting‐controlled self‐assembly of the nanoparticles and charged polymers to generate a cable‐like nanostructure with the aid of a vacuum. The nanocables have an outer diameter of ca. 100 nm with a polycrystalline ZnO inner core of 7–25 nm in diameter. The length and morphology of the nanocables are determined by external vacuum conditions as well as the ZnO concentration in the composite. A photoluminescence study shows an enhanced green light emission arising from ZnO with a size‐dependence feature.

TEM image of a PEDOT/PSS‐ZnO nanocable at high magnification.     

Oriented Synthesis of One‐Dimensional Polypyrrole Molecule Chains in a Metal‐Organic Framework

We report for the first time the preparation of single polypyrrole (PPy) molecule chains using a “metal‐organic framework” with 1 nm channels as a template. The obtained one‐dimensional (1‐D) PPy has highly structure order and excellent conductivity, which has improved by as much as five orders of magnitude in comparison with that of 2‐D PPy.

     

Nanofibers Self‐assembled from Structural Complementary Borono‐decapeptides

A series of structural complementary decapeptides with phenyl boronic acid tails or borono‐decapeptides (BPs) were designed and synthesized for supramolecular self‐assembly. After dissolving these borono‐decapeptides in deionized (DI) water, well‐defined nanofibers were formed in BP1 (B(OH)₂VEKELVKEKL‐OH) and BP3 (B(OH)₂AELELARARL‐OH). It was found that the self‐assembled borono‐decapeptide BP1 and BP3 have a parallel β‐sheet conformation in the formed nanofibers. The strategy demonstrated here shows a great prospect in preparation of well‐ordered nanofibers via rationally designing the molecular structures of peptides.

     

Photodissociation Rate Constants of New Light Sensitive Alkoxyamines

The photochemical properties of two new photocleavable alkoxyamines bearing a benzophenone‐derived chromophore were studied by electron spin resonance (ESR). The C O bond cleavage has been demonstrated and the photolysis rate constants (k_d) determined over a large range of light intensity through the monitoring of the nitroxide concentration in aerated conditions. The obtained kinetic data highlight for the first time the linear dependence of k_d on the light intensity for alkoxyamines: this should be a driving factor for nitroxide mediated radical photopolymerization (NMP²).

     

Nonaggregated Zinc Phthalocyanine in Mesoporous Nanocrystalline TiO2 Thin Films

Summary: A simple sonochemical approach has been successfully developed to deposit poorly dissolved phthalocyanine dyes onto the surface of a highly‐ordered mesoporous nanostructured TiO₂ thin film. The aggregation‐free phthalocyanines are effectively encapsulated and stabilized in the nanopore arrays of the zeolite‐like mesoporous nanocrystalline TiO₂ thin film. Highly dispersed dye∥TiO₂ heterojunction arrays with a large contact area can be obtained by using this interesting approach.

The incorporation of phthalocyanine dyes into the surface of a highly‐ordered mesoporous nanostructured TiO₂ thin film, a potential photocatalyst.     

Heparin‐Controlled Growth of Polypyrrole Nanowires

Summary: Heparin, a potent anticoagulant, has been used for the first time for the synthesis of PPy nanowires serving not only as an anion dopant but also as an effective morphology‐directing agent. The obtained PPy nanowires exhibit long and fine structures with smooth surface and the average diameter of the nanowires is about 90–100 nm and lengths are several hundred nanometers to micrometers. The possible formation mechanism of PPy nanowires may be related to the chain structure of heparin with functional groups ( SO and  COO⁻) on the surface. The effect of concentrations of pyrrole monomers and heparin on the morphology and size of PPy nanowires has been investigated.

SEM image of PPy nanowires synthesized in the presence of heparin.     

“Click” Dielectrics: Use of 1,3‐Dipolar Cycloadditions to Generate Diverse Core‐Shell Nanoparticle Structures with Applications to Flexible Electronics

We have synthesized a “universal ligand” incorporating a phosphonate surface anchor and a terminal alkyne moiety which binds to TiO₂ nanoparticles and exhibits excellent dispersity in organic solvents. The alkyne functionality permits attachment of azide terminated polymer shells using “click” chemistry. Thus TiO₂ core nanoparticles have been encapsulated with both polystyrene and poly(t‐butyl acrylate) shells. The TiO₂‐poly(t‐butyl acrylate) core shell nanoparticles are amenable to further chemical transformation into TiO₂‐poly(acrylic acid) nanoparticles through ester hydrolysis. These TiO₂‐polyacrylic acid nanoparticles are dispersible in aqueous solution. The resulting core‐shell nanoparticles have been incorporated as high K dielectric films in capacitor and organic thin film transistor devices and are promising new materials for flexible electronics applications.

     

The Shielding Effect of Nano TiO2 on Collagen under UV Radiation

The shielding effect of nano TiO₂ on collagen under UV radiation was investigated using UV spectrophotometry. The results indicate that the shielding of collagen under UV radiation in the presence of nano TiO₂ is significant. For 2.5 wt.‐% of TiO₂, there is a greater shielding effect of UV radiation than that for 0.5 wt.‐% of TiO₂. In addition, this study gives hints that a novel tanning agent with a UV shielding function can be formulated by using nano TiO₂.

UV absorption of collagen under UV radiation after adding 2.5 wt.‐% TiO₂.     

Decorating Polypyrrole Nanotubes with Au Nanoparticles by an In Situ Reduction Process

Au nanoparticle‐decorated polypyrrole nanotubes (defined as PPy/Au nanocomposites) are prepared by an in situ reduction process. Polypyrrole (PPy) nanotubes are prepared by a self‐degraded template method, and Au nanoparticles are deposited in situ by the reduction of HAuCl₄. The size and uniformity of the Au nanoparticles that decorate the PPy nanotubes can be controlled by adjusting the experimental conditions, such as the stabilizers used and the reaction temperature. The morphologies and optical properties of the nanocomposites have been characterized by scanning electron microscopy, transmission electron microscopy, UV‐vis, and FT‐IR spectroscopy. Conductivity measurements show that the conductivities of the nanocomposites decrease with a decrease of temperature, and the conductivity–temperature relationship obeys the quasi‐one dimensional variable range hopping model.

     

Photoinduced Charge Separation in an Aqueous Phase Using Nanoporous TiO2 Film and a Quasi‐Solid Made of Natural Products

Solar cells comprised of nanoparticulate TiO₂ porous film photosensitized with an adsorbing dye have been utilized as photoinduced charge separation systems in aqueous media with the view to forming future artificial photosynthetic systems able to create fuels from solar energy and water. The photoinduced charge separation of the sensitized TiO₂ cell in a quasi‐solid, made from agarose or κ‐carrageenan, was investigated.

I–V curves under 98 mW · cm⁻² irradiation of ITO/TiO₂/Ru(dcbpy)₂(NCS)₂. Electrolyte: 0.1 M LiI/0.01 M I₂ in a quasi‐solid of 0.2 wt.‐% gelatin containing a large excess of water.     

Facile Synthesis of Double‐Shelled Polypyrrole Hollow Particles with a Structure Similar to That of a Thermal Bottle

Polystyrene (PS) hollow spheres containing a hole on the surface were used as templates to fabricate double‐shelled polypyrrole (PPy) hollow particles with a unique structure similar to that of a thermal bottle. Thanks to the hole on the surface, the monomer and initiator could easily and quickly diffuse into the interior of the PS hollow sphere to generate uniform PPy coatings on both the inner and outer surfaces of the hollow template. When the PS template was selectively removed with tetrahydrofuran, we obtained a double‐shelled hollow particle with a structure resembling that of a thermal bottle. We also demonstrated that the morphology and porosity of the resultant PPy coatings could be manipulated and fine‐tuned by adjusting at least three parameters: the concentration of monomer, the polymerization time, and the addition of poly(vinyl pyrrolidone).

     

Coordination‐Polymeric Nanofibers and their Field‐Emission Properties

The large‐scale fabrication of nanofibers of coordination polymers (CPs) is reported for the first time from CP gel precursors by the electrospinning method. In the absence of organic polymeric additives, viscous solutions suitable for drawing fibers have been made by diluting the gel precursors, which are obtained by mixing Ni(OAc)₂ and 4‐trifluoromethylbenzoic acid with 4,4′‐bis(pyridyl)ethylene (bpe) or 4,4′‐bipyridine (bpy) linear spacer ligands in organic solvents. One‐dimensional polymeric structures have been proposed for these gels and nanofibers based on the crystal structures of the compounds isolated. These fibers show some interesting field‐emission properties. The results described here may well be extended to other one‐dimensional polymers, thus opening the door for processing of the coordination polymers.

     

Preparation of Nanostructured Polyaniline and its Super‐Amphiphilic Behavior

PANI nanofibers are prepared electrochemically by template‐free method on a stainless steel electrode. Both the hydrophilicity and the lipophilicity of the modified SS surface are enhanced by the nanostructured PANI, and a super‐amphiphilic surface is obtained in this way. The influence of polymerization conditions, such as polymerization potentials, polymerization time, the acidity, and the dopants on the super‐amphiphilic property, has been systematically investigated. In addition, the mechanisms of obtaining a super‐amphiphilic surface are briefly discussed.

     

Fabrication of Au/Titania Composite Nanodot Arrays from Au‐Loaded Block Copolymer Micellar Films

Summary: A simple route to an ordered array of metal/semiconductor oxide composite nanodots is presented. Micellar monolayer films of polystyrene‐block‐poly(2‐vinyl pyridine) (PS‐b‐P2VP) loaded with HAuCl₄ in the P2VP nanodomains are used as templates. TiO₂ is generated selectively within the polar P2VP domains of PS‐b‐P2VP/HAuCl₄ films by chemical vapor deposition of TiCl₄. Subsequent removal of the organic matrix by oxygen plasma or UV light leads to an array of Au/TiO₂ composite nanoparticles on the substrate surface.

Schematic illustration of the process to fabricate an array of Au/titania composite nanodots.     

Facile Fabrication of Functional Polypyrrole Nanotubes via a Reactive Self‐Degraded Template

Summary: Polypyrrole nanotubes with high electric conductivity and azo function have been fabricated in high yield via an in‐situ polymerization. During the process fibrillar complex of FeCl₃ and methyl orange (MO), acting as a reactive self‐degraded template, directed the growth of polypyrrole on its surface and promoted the assembly into hollow nanotubular structures.

TEM image of uncompleted PPy nanotubes synthesized in MO solutions after reaction for 40 min.     

Synthesis of Poly(ethylene oxide)s Bearing Functional Groups along the Chain

Well‐defined poly(ethylene oxide)s (PEOs) bearing reactive sites regularly distributed along the chain have been synthesized by the polycondensation of PEO containing a central tertiary amino group with dichloromethane, followed by quaternization with suitable reagents to obtain polyzwitterionic or cationic PEOs with alkyl, allyl, or fluorocarbon pendant groups. The pendant allyl groups have been converted into primary amino groups by reaction with 2‐aminoethanethiol hydrochloride to obtain polyamino‐functionalized PEO.

Polyfunctional PEOs bearing different pendant groups.