Strategy for the syntheses of isolated fine silver nanoparticles and polypyrrole/silver nanocomposites on gold substrates

In this work, isolated fine silver nanoparticles and polypyrrole/silver nanocomposites with diameters of about 10 nm on gold substrates were first prepared by electrochemical methods. First, an Ag substrate was cycled in a deoxygenated aqueous solution containing 0.1 M HCl from −0.30 to +0.30 V versus Ag/AgCl at 5 mV/s with 30 scans. Subsequently the Ag working electrode was immediately replaced by an Au electrode and a cathodic overpotential of 0.2 V was applied under controlled sonication to synthesize Ag nanoparticles on the Au electrode. Then pyrrole monomers were encouragingly found to be polymerized on the deposited Ag nanoparticles. This polymerization is distinguishable from the known chemical or electrochemical one, due to the electrochemical activity of unreduced species of Ag_n⁺ clusters inside the nanoparticles. Also, this polymerization may be ascribed to the oxidizing agent of AuCl₄⁻, which is present on the Au electrode.     

Catalytic electroxidation pathway for the polymerization of polypyrrole in the presence of ultrafine silver nanoparticles

In this work, we report the first electrochemical polymerization of polypyrrole (PPy) on Au substrates in aqueous solutions containing additives of prepared Ag nanoparticles with a diameter less than 2 nm. Due to the effect of Ag nanoparticles, which can provide a catalytic electroxidation pathway for the polymerization of PPy, the synthesized PPy film demonstrates some novel characteristics. It shows a finer and granular raspberry morphology with nano-scaled particles, and a rougher surface. The conductivity of PPy is significantly increased (∼8 times), which also reflects on the extremely high oxidation level of 0.35 revealed from the analysis of X-ray photoelectron spectroscopy (XPS). The mechanism of the nucleation and growth was investigated to explain the specific characteristics of PPy films.     

Facile synthesis of polypyrrole nanospheres and their carbonized products for potential application in high-performance supercapacitors

A facile method to prepare uniform polypyrrole (PPy) nanospheres is developed by using 3-chloroperbenzoic acid as oxidant, structure-induced reagent and dopant for polymerization of pyrrole without introducing extra acid, template and surfactant. The as-synthesized PPy nanospheres with an average diameter of 100–200 nm and conductivity about 10⁻² S cm⁻¹ are characterized by SEM, FTIR, UV–vis spectroscopy, XRD and elemental analysis in an effort to determine the identity of the nanospheres and the mechanism relevant to their formation and stabilization. Influences of experimental conditions on the morphology of the PPy nanospheres have been investigated. Via the high temperature pyrolyzation at 900 °C, the nitrogen-doped carbon nanospheres have been obtained from the PPy nanospheres precursors, which have a high conductivity of 10–100 S cm⁻¹, showing a good potential as the electrode materials for high-performance supercapacitors due to their excellent electrochemical performance.     

Optimization of electrochemical polymerization parameters of polypyrrole on Mg–Al alloy (AZ91D) electrodes and corrosion performance

We report on the optimum electropolymerization conditions of polypyrrole (PPy) coatings on Mg alloy AZ91D electrodes from aqueous electrolytes of sodium salicylate via cyclic voltammetry (CV). Results show that initial and end potential values during the electrochemical coating procedure play an important role on the adhesion and corrosion performance of PPy films. Corrosion tests of AZ91D electrodes coated with PPy under optimized conditions show a good corrosion performance during 10 days in Na₂SO_4, without peeling off of these thin films.     

Electrochemical synthesis of bilayer coatings of poly(N-methylaniline) and polypyrrole on mild steel and their corrosion protection performances

Homopolymer and bilayer coatings of poly(N-methylaniline) (PNMA) and polypyrrole-dodecylsulfate (PPy-DS) have been electropolymerized on a mild steel (MS) surface by the potentiodynamic method in aqueous oxalic acid solutions. In order to include dodecylsulfate ion as dopant in the polypyrrole, sodium dodecylsulfate was also added to the polymerization solution of pyrrole. Characterization of coatings was carried out by the cyclic voltammetry, Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). Corrosion behavior of the polymer coated MS electrodes was investigated in highly aggressive 0.5 M HCl solution by the Tafel test and electrochemical impedance spectroscopy (EIS) techniques. Corrosion test revealed that among the protective coatings obtained, the PNMA/PPy-DS bilayer exhibited the best corrosion resistance at all immersion times.     

Microwave-assisted synthesis of BSA-protected small gold nanoclusters and their fluorescence-enhanced sensing of silver(I) ions

A one-step microwave-assisted method is used for the synthesis of small gold nanoclusters, Au(16)NCs@BSA, which are used as a fluorescence enhanced sensor for detection of silver(I) ions with high selectivity and sensitivity.     

Research progress in the electrochemical synthesis of ferrate(VI)

There is renewed interest in the +6 oxidation state of iron, ferrate (VI) (Fe^VIO₄²⁻), because of its potential as a benign oxidant for organic synthesis, as a chemical in developing cleaner (“greener”) technology for remediation processes, and as an alternative for environment-friendly battery cathodes. This interest has led many researchers to focus their attention on the synthesis of ferrate(VI). Of the three synthesis methods, electrochemical, wet chemical and thermal, electrochemical synthesis has received the most attention due to its ease and the high purity of the product. Moreover, electrochemical processes use an electron as a so-called clean chemical, thus avoiding the use of any harmful chemicals to oxidize iron to the +6 oxidation state. This paper reviews the development of electrochemical methods to synthesize ferrate(VI). The approaches chosen by different laboratories to overcome some of the difficulties associated with the electrochemical synthesis of ferrate(VI) are summarized. Special attention is paid to parameters such as temperature, anolyte, and anode material composition. Spectroscopic work to understand the mechanism of ferrate(VI) synthesis is included. Recent advances in two new approaches, the use of an inert electrode and molten hydroxide salts, in the synthesis of ferrate(VI) are also reviewed. Progress made in the commercialization of ferrate(VI) continuous production is briefly discussed as well.     

Synthesis,characterization of Fe3O4@glycine doped polypyrrole magnetic nanocomposites and their potential performance to remove toxic Cr(VI)

Fe₃O₄ coated glycine doped polypyrrole magnetic nanocomposite (Fe₃O₄@gly-PPy NC) was prepared via coating of suspended Fe₃O₄ nanoparticles with gly-PPy. FE-SEM and HR-TEM images indicated that Fe₃O₄ nanoparticles were encapsulated by precipitating gly-PPy moieties. Chromium(VI) adsorption followed a Langmuir isotherm with maximum capacity of 238–303 mg/g for a temperature range of 25–45 °C at pH 2. The adsorption process was governed by the ionic interaction and the reduction of Cr(VI) to Cr(III) by the PPy moiety. Results showed that NCs are effective adsorbents for the removal of Cr(VI) from wastewater and can be separated by external magnetic field from the reactor.     

Influence of pH on the synthesis and properties of polypyrrole on copper from phytic acid solution for corrosion protection

Polypyrrole (PPy) films were deposited on copper from “green” inhibitor of phytic acid solution for corrosion protection of copper. The corrosion protection property of the PPy layer was studied by an immersion test in a NaCl aqueous solution. The polymerization process of PPy on copper changed with the pH values of phytic acid solution and current density applied. When one oxidized bare copper in phytic acid solution at various pHs containing pyrrole monomer, a thin layer consisting of complex compound of Cu-phytate was firstly formed, followed by the formation of the PPy layer doped with phytate anion on the complex compound layer. The complex compound layer passivated the copper surface and its thickness increased with the lower pH value of the solution and the lower current density applied. It was found that the PPy coating prepared in the phytic acid solution at pH 4 exhibit the most protective property against copper corrosion.     

Characterization of polypyrrole/piperazine-1,4-bis(2-ethane sulfonate) film and its application for the immobilization of vitamin B12

Vitamin B12 (B12) - possessing a redox active cobalt centre - is a candidate to be used as a mediator in bioelectrochemical processes. In order to exploit the possible redox activity of B12, Pt has been modified by a bio-conform conducting layer polypyrrole/piperazine-1,4-bis(2-ethane sulfonate) PPy/PIPES. The electrochemical and spectral behaviour of this film proved to be similar to PPy/dodecyl-sulfate (DS), widely considered and accepted as one of the best combinations of conducting polymer films. The capability of the PPy/PIPES film for acting as adsorbant in the accumulation of B12 has been evidenced by the electrochemical quartz crystal microbalance (EQCM) technique. B12 could also be incorporated into the polymer layer during its electrochemical deposition. The results proving the preserved redox activity of B12 within the film open new perspectives towards redox mediated bioelectrochemical applications based on the immobilization of this biomolecule.     

The electrochemical synthesis of poly(aniline-co-o-anisidine) on copper and their corrosion performances

The copolymer films PANI-co-POA and poly(aniline-co-o-anisidine) were carried out on copper (Cu) electrode, by applying two different scan rates (20 and 50 mV s⁻¹) and using two different thicknesses at high scan rate. Synthesizes were achieved under cyclic voltammetric conditions from 0.075 M aniline and 0.075 M o-anisidine containing sodium oxalate solutions. The synthesized copolymer films were strongly adherent and homogeneous in both cases. AC impedance spectroscopy (EIS), anodic polarization plots and open circuit potential–time curves were used to evaluate the corrosion performance of copolymer coated and uncoated electrodes in 3.5% NaCl. It was shown that the copolymer film coated at low scan rate exhibited a better property initially when compared with the copolymer film produced at high scan rate. However, it could not resist the attack of corrosion products, in longer time and meanwhile its barrier property significantly diminished. It was found that the thin copolymer film produced at high scan rate by its catalysing effect led to the formation of highly protective copper oxides on the surface whereby providing a better protection for long exposure times. It also emerged that the corrosion resistances of thin copolymer film produced at high scan rate and copolymer film synthesized at low scan rate were almost same and relatively higher for much longer periods when compared with the one observed for bare copper electrode.     

New soluble unsaturated polyketone derived from diarylidenecycloalketone: synthesis and optical and electrochemical properties of π-conjugated poly(diarylidenecyclohexanone) with long side chains

A new type of unsaturated polyketone having cyclohexanone moiety in a π-conjugated main chain was prepared by polycondensation between 2,6-bis(4-bromobenzylidene)cyclohexanone and 2,5-dihexyloxy-p-phenylene diboric ester in the presence of Pd(PPh₃)₄. The polymer had good solubility in common organic solvents. Analysis by gel permeation chromatography (GPC; polystyrene standards) showed that the polymer had M_n and M_w values of 7800 and 18?200, respectively. The polymer exhibited a [η] value of 0.70 dl g⁻¹ in benzene at 30 °C. The chloroform solution of the polymer showed an UV-Vis peak at 392 nm, and the PL spectrum gave a peak at 533 nm. DSC exhibited that the polymer had a T_g of 85 °C. The DSC data, observation with a polarizing microscope, X-ray diffraction data and UV-Vis data of the obtained polymer showed a phase transition above 200 °C. TGA showed that the polymer had good thermal stability with 5 wt% loss temperature of 407 °C under N₂. Electrochemical oxidation (or p-doping) of the polymer started at about 0.7 V vs. Ag/AgNO₃ and gave a peak at 1.06 V vs. Ag/AgNO₃ with a color change of the film from yellow to deep red. The color change was followed by UV-Vis spectroscopy. The corresponding p-dedoping peak appeared at 0.58 V vs. Ag/AgNO₃.     

Hydrothermal synthesis of uniform Fe-doped Gd(OH)3 nanorods and their magnetic properties: Phase conversion from paramagnetism to ferromagnetism

High quality pure and Fe-doped Gd(OH)₃ nanorods were fabricated through a template-free hydrothermal method for the first time. Analysis of XRD indicates that Fe³⁺ was incorporating in the interstitial sites rather than occupying the substitutional sites, forming pure hexagonal structure of Gd(OH)₃ without any other impurity phase. TEM characterizations show that all the samples perform uniform rod-like morphologies with similar diameter and length, which suggests that the Fe doping has little influence on the morphologies of samples. ICP and XPS spectra suggest that the dopant Fe³⁺ is incorporated into the inner body sites, not on the surface of nanorods. Magnetic studies show that the magnetic phase can be converted from paramagnetism to room-temperature ferromagnetism by doping Fe³⁺ ions into the Gd(OH)₃ nanorods. The saturation magnetization (Ms) is sensitive to the amount of Fe dopants, and the Ms for Fe_0.03Gd_0.97(OH)₃ nanorods reaches the maximum value of 0.184 emu/g. It is considered that the ferromagnetic ordering is possibly originated from the exchange interaction of Fe³⁺ through the oxygen vacancies, leading to the formation of point defect-mediated bound magnetic polarons (BMPs). Ruling out the affect of morphologies and secondary magnetic phase on the magnetic properties, the ferromagnetic ordering in uniform Fe-doped Gd(OH)₃ nanorods, in which the dopant Fe³⁺ is incorporated into the inner body sites of nanorods, are of great importance to deeply understand the rare earth-based DMS/DMD systems and have potential applications in spintronic devices.     

Recent advances in the use of tri(2-furyl)germane,triphenylgermane and their derivatives in organic synthesis

Tri(2-furyl)germane is a readily prepared, easy-to-handle, and storable triorganogermane. The three 2-furyl groups confer unique reactivity on it in a variety of reactions. Tri(2-furyl)germane is a promising alternative to tributyltin hydride in radical reaction, especially superior in radical addition to alkenes. The hydrogen of tri(2-furyl)germane is so acidic that generation of the corresponding germyl anion is achieved with the aid of weak bases, such as potassium tert-butoxide and cesium carbonate. The anion participates in nucleophilic addition to aldehydes, 1,4-addition to α,β-unsaturated carbonyl compounds, and coupling reaction with aryl and vinyl halides under palladium catalysis. Palladium-catalyzed hydrogermylation with tri(2-furyl)germane create some novel phenomena. Some chemistry of triphenylgermane will be described.     

5-(2-羟基苯基)-10,15,20-三苯基卟啉及其衍生物的新法合成

在二甲苯溶液中,以氯乙酸作催化剂,在132℃及常压下合成了5－（2－羟基苯基）－10,15,20－三苯基卟啉等3种不对称卟啉。产物经红外光谱、紫外可见光谱等进行了表征。研究了反应时间、反应物比例、温度、浓度等对收率的影响,在优选的反应条件下,产物收率可达6．3％。     

Facile synthesis of thiol-terminated poly(styrene-ran-vinyl phenol) (PSVPh) copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization and their use in the synthesis of gold nanoparticles with controllable hydrophilicity

A facile approach to prepare thiol-terminated poly(styrene-ran-vinyl phenol) (PSVPh) copolymers and PSVPh-coated gold nanoparticles is reported with the goal of creating stabilizing ligands for nanoparticles with controlled hydrophilicity. Dithioester-terminated poly(styrene-ran-acetoxystyrene) copolymers were synthesized via RAFT polymerization using cumyl dithiobenzoate as a chain transfer agent. These copolymers were converted to thiol-terminated PSVPh copolymers by a one step hydrazinolysis reaction using hydrazine hydrate to simultaneously convert dithioester-terminal and acetoxy-pendant groups to thiol-terminal and hydroxyl-pendant groups, respectively. Spectroscopic observations including NMR and IR confirm end- and pendant-group conversion. PSVPh-coated gold nanoparticles were synthesized in the presence of a mixture of thiol-terminated PSVPh and PSVPh copolymers containing disulfides as stabilizing ligands in a water/toluene, two-phase system. The size and size distribution of core gold nanoparticles were determined by TEM and image analysis. The hydrodynamic radius of PSVPh-coated gold nanoparticles was also determined by dynamic light scattering experiment, which confirms the particle analysis by TEM. This procedure provides a facile technique to control the polarity and hydrophilicity of metal nanoparticle surfaces and could prove critical in advancing the control of nanoparticle placement in biological and hierarchically ordered systems, such as diblock copolymers.     

Mechanism analysis of the PEG-participated Gilch synthesis for soluble poly(p-phenylene vinylene) derivatives

By introducing poly(ethylene glycol) (PEG) into the Gilch reaction system for the synthesis of soluble poly(p-phenylene vinylene)s (PPVs), significant changes were observed. First, with the involvement of PEG, the polymerization degree increases significantly and the molecular weight distribution becomes wider. The multimodial characteristic of the GPC curves at low conversions is quite evident. Second, at low PEG content, gelation dramatically disappears; with an increase of PEG, gelation reappears. From the above experimental results, the existence of various types of polymerization-active species and the anionic polymerization mechanism are confirmed, which are due to the dissociation of the carbanion–cation pairs by the complexing effect of PEG. At the same time, the enhanced dissociation of the base (t-BuO⁻K⁺) ion pairs by PEG may be responsible for the dramatic disappearance of gelation. Free t-BuO⁻ anions have strengthened the basicity and accelerated the conjugation-formation process which competes with the interchain by-reactions. Gelation is therefore avoided. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 263–268, 2001     

Electrochemical fabrication and electrocatalytic characteristics studies of gold nanopillar array electrode (AuNPE) for development of a novel electrochemical sensor

Gold nanopillar array electrodes were prepared by electrochemical deposition of gold into the nanopores of anodic aluminum oxide membrane placed onto the gold thin film electrode surface, which was in advance modified with cysteamine self-assembled monolayer as an anchoring layer. The Au nanopillar electrode is electrochemically stable and consists of highly dense, upstanding pillars assembled on the cysteamine monolayer. The structural morphology and chemical composition of the nanoarray electrode was characterized by field emission scanning electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Electrochemical measurements indicate that the Au nanopillar electrode possesses high electrocatalytic activities in the reduction of hydrogen peroxide and molecular oxygen, especially in glucose oxidation due to its higher electroactive surface area. The electro-oxidation studies of several electroactive neurotransmitters demonstrate that the nanopillar electrode can be utilized as a promising material for the construction of novel electrochemical sensor.     

Effect of synthesis routes on the performance of hydrated Mn(IV) oxide-exfoliated graphite composites for electrochemical capacitors

MnO₂ · nH₂O-EG composites for electrochemical capacitors were prepared using commercially available low cost exfoliated graphite (EG) as a conductive substrate, and (a) potassium permanganate and (b) manganese(II) acetate solutions by two different routes. Method (1) was addition of EG to (a), followed by 1 h stirring and then slow addition of (b), and in Method (2) the solutions (a) and (b) were swapped. Using Method (1) submicron or smaller sized MnO₂ · nH₂O particles having mesopores were formed, whereas Method (2) produced lumps of aggregated particles of several tens microns without mesopores, though specific surface areas were not very different and both were similar by XRD. Although EG alone showed only about 2 F g⁻¹, the capacitance per net amount of MnO₂ in 1 mol L⁻¹ Na₂SO₄ solution increased proportionally with EG content and was always larger by Method (1) than Method (2), that is, the utilization ratio of MnO₂ increased with EG content and the effect was more prominent in the case of Method (1). The results indicated that EG is a good conductive material for MnO₂ · nH₂O electrochemical capacitors if appropriate synthesis processes are used. The performance of the composites strongly depends on synthesis method, even using the same raw materials. It was suggested that the morphology of the products was a primary factor leading to different performance rather than composition.     

New and convenient synthesis of (R)-(+)-4, 5-Dihydro-4-methyl-2(3H)-furanone and (R)-(-)-4-Bromo-3-methyl-1-O-tert-butyldimethyl-silylbutan-1-ol

A convenient partial synthesis of the lactone (+)- 10 is reported starting from the readily available methyl (S)-(+)-3-hydroxy-2-methylpropanoate (+)- 1 . Furthermore, an efficient three step route to the optically active saturated isoprene unit (-)- 13 in high yield starting from the lactone (+)- 10 is reported for the first time.