One-step Electrochemical Synthesis Research Articles

Direct and Freely Switchable Detection of Target Genes Engineered by Reduced Graphene Oxide-Poly(m-Aminobenzenesulfonic Acid) Nanocomposite via Synchronous Pulse Electrosynthesis

A novel one-step electrochemical synthesis of the reduced graphene oxide and poly(m-aminobenzenesulfonic acid, ABSA) nanocomposite (PABSA-rGNO) via pulse potentiostatic method (PPM) for direct and freely switchable detection of target genes is presented. Unlike most electrochemical preparation of hybrids based on rGNO and polymer, electrochemical synthesis of PABSA (during the pulse electropolymerization period of PPM) and electrochemical reduction of rGNO (during the resting period of PPM), in this paper, were alternately performed. The total progress synchronously resulted in PABSA-rGNO nanocomposite. This nanocomposite was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The PABSA-rGNO nanocomposite integrated graphene (a single-atom thick, two-dimensional sheet of sp(2) bonded conjugated carbon) with PABSA (owning rich-conjugated structures, functional groups, and excellent electrochemical activity), which could serve as an ideal electrode material for biosensing and electrochemical cell, etc. As an example, the immobilization of the specific probe DNA was successfully conducted via the noncovalent method due to the π-π* interaction between conjugated nanocomposite and DNA bases. The hybridization between the probe DNA and target DNA induced the product dsDNA to be released from conjugated nanocomposite, accompanied with the self-signal regeneration of nanocomposite ("signal-on"). The self-signal changes served as a powerful tool for direct and freely switchable detection of different target genes, and the synergistic effect of PABSA-rGNO nanocomposite effectively improved the sensitivity for the target DNA detection.

3D hierarchically porous Cu–BiOCl nanocomposite films: one-step electrochemical synthesis, structural characterization and nanomechanical and photoluminescent properties

Three-dimensional (3D) hierarchically porous composite Cu-BiOCl films have been prepared by a facile one-step galvanostatic electrodeposition process from acidic electrolytic solutions containing Cu(ii) and Bi(iii) chloride salts and Triton X-100. The films show spherical, micron-sized pores that spread over the whole film thickness. In turn, the pore walls are made of randomly packed BiOCl nanoplates that are assembled leaving micro-nanopore voids beneath. It is believed that Cu grows within the interstitial spaces between the hydrogen bubbles produced from the reduction of H(+) ions. Then, the BiOCl sheets accommodate in the porous network defined by the Cu building blocks. The presence of Cu tends to enhance the mechanical stability of the composite material. The resulting porous Cu-BiOCl films exhibit homogeneous and stable-in-time photoluminescent response arising from the BiOCl component that spreads over the entire 3D porous structure, as demonstrated by confocal scanning laser microscopy. A broad-band emission covering the entire visible range, in the wavelength interval 450-750 nm, is obtained. The present work paves the way for the facile and controlled preparation of a new generation of photoluminescent membranes.

Effects of sodium hydroxide on the yield and electrochemical performance of sulfonated poly(ether-ether-ketone) functionalized graphene

An environmentally friendly method for the one-step electrochemical synthesis of water dispersible graphene directly from graphite is reported. Sulfonated poly(ether-ether-ketone) (SPEEK) dissolved in deionised water was used as an electrolyte and a surface modifying agent for graphene. The effects of sodium hydroxide (NaOH) on the production yield and electrochemical performance of graphene were investigated in detail. The production yield of few-layer graphene increased to above 40%, as compared to the 6% in the absence of NaOH. Fourier transform infrared and X-ray photoelectron spectroscopy (XPS) analyses suggested that the oxygen functionalities (hydroxyl and carboxyl) generated during the electrochemical exfoliation of graphite in the absence of NaOH were decreased significantly during the electrolysis experiment in an alkaline solution of SPEEK. This is attributed to the NaOH induced reduction of oxygen functionalities present on the surface of graphene sheets. XPS elemental analysis also confirmed the removal of oxygen functionalities in an alkaline medium during the graphite exfoliation experiment. Transmission electron microscopy and atomic force microscopy analyses confirmed the formation of single layer functionalized graphene. A charge–discharge experiment showed that the specific capacitance of the as-prepared graphene in the absence of NaOH was 18 F g−1 at a current density of 2.2 A g−1. In contrast, the specific capacitance was increased to 244 F g−1 for graphene prepared under alkaline condition indicating its suitability as an energy storage electrode material. The high electrochemical performance may be due to the large surface area of graphene (433 m2 g−1) prepared under alkaline condition as observed by the Brunauer–Emmett–Teller surface area analysis.

One-step electrochemical synthesis of Pt–CeO2 composite thin films on a glassy carbon electrode

A Pt–CeO2 composite thin film was prepared on a glassy carbon electrode by one-step electrochemical deposition technique. The film was constructed of Pt particles well dispersed and embedded in a porous CeO2 substrate. The prepared Pt–CeO2/GC electrode showed a better catalytic performance toward methanol electrooxidation compared with the bulk Pt electrode.

One-step electrochemical synthesis and physico-chemical characterization of CdSe nanotubes

Stoichiometric CdSe nanotubes (NTs) with a length of ∼700nm have been successfully grown by one-step electrochemical technique into anodic alumina membranes. Cyclovoltammetric method has been performed using porous anodic alumina as template electrode and an electrochemical bath containing Cd2+ ions and SeO2. The as-prepared NTs have been identified as face-centred-cubic CdSe by XRD, while micro-Raman analysis reveals the typical peaks of nanostructured CdSe. The stoichiometric deposition of CdSe NTs formation is suggested by EDX analysis, with an average atomic percentage of Cd:Se of ∼0.93. Photoelectrochemical measurements reveal that CdSe NTs are photoactive materials with direct band gap of 1.75eV and n-type semiconducting behaviour.

Electrochemical growth of hierarchical CuSn nanobrushes from an ionic liquid

One-step electrochemical synthesis of hierarchical single crystalline copper–tin nanobrushes is achieved in a room temperature 1-ethyl-3-methylimidazolium dicyanamide ionic liquid containing 0.016 M Cu(I) and 0.033 M Sn(II) at a low current density of − 0.4 mA cm − 2 . This study also shows that morphologies of the deposits can be manipulated by the Cu(I)/Sn(II) concentrations in the solution, and thus, offers a method for reproducible preparation of the nanobrushes.

Cyclopolymerization of α-methylbenzyl dipropargylamine by transition metal catalysts

π-Conjugated oligomers and polymers are intensively studied mainly because of their interesting electrical and optical properties and, more importantly, their potential utility in electronics and photonic applications. Among the π-conjugated polymers, the polyacetylene (PA) is structurally the simplest one, and it can be made freestanding thin film by using Shirakawa catalysts [Ti(OC4H9)4Al(C2H5)3]. 6 However, the drawbacks are that PA is insoluble, infusible, and unstable to air oxidation. Thus it was difficult for practrical applications to opto-electronic devices as an active material. To overcome these problems of PA itself, more stable heterocycle-based polymers such as polypyrrole and polythiophene were prepared, and these materials can be easily obtained in their oxidized conducting form by means of one-step electrochemical synthesis. And also, a number of substituted PAs has been prepared by the simple linear polymerization of the corresponding acetylene monomers by various catalyst systems. The polymers having a conjugated backbone are expected to show unique properties such as electrical conductivity, paramagnetism, migration and transfer of energy, color, and chemical reactivity and complex formation ability. Because of these properties, polyacetylene and its homologues have been promising as organic semiconductors, as membranes for gas separation and for liquid-mixture separation, as chiro-optical materials, as side-chain liquid crystals, and as materials for nonlinear optical property and for photoluminescence and electroluminescence properties. Cyclopolymerization of nonconjugated diynes is very interesting method for the synthesis of conjugated polymer system via an alternating intramolecular-intermolecular chain propagation. 1,6-Heptadiyne itself has been polymerized by various transition metal catalysts into a polyene of cyclic structure. The resulting poly(1,6-heptadiyne)s obtained were dark red or black, which indicates a high order of conjugation in the polymer. However, the poly(1,6-heptadiyne)s were also insoluble in any organic solvent and unstable to air oxidation as like with that of PA. Introduction of substituents at 4-position of 1,6-heptadiyne can help enhance the processibility and stability of the polyene systems, thus a variety of substituted poly(1,6-heptadiyne)s were designed and synthesized. In recent years, nitrogen-containing polymers have received unabated attention in the design and synthesis of multifunctional polymers. Unlike other π-conjugated polymers, they contain nitrogen heteroatom either in the main chains or in the side chains that provide facile quaternarization reaction and protonation of the nitrogen sites. Now, we report the synthesis of new conjugated cyclopolymer by the cyclopolymerization of a dipropargylamine derivative and the characterization of the resulting conjugated polymer.

Novel KOH electrolyte for one-step electrochemical synthesis of high purity solid K 2FeO 4: Comparison with NaOH

An electrosynthesis from an iron wire gauze in KOH electrolyte is first presented for the in situ direct synthesis of the solid K 2FeO 4, with a highest efficiency of 73.2%, purities of 95.3–98.1% and a highest yield of 49 g l −1 K 2FeO 4 at 65 °C, which is far better than that in NaOH electrolyte as a whole. A variety of electrolysis conditions including cell configuration, applied current density, temperature and electrolyte concentration have been explored. The in situ and ex situ electrochemically directly synthesized K 2FeO 4 powders exhibit similar IR absorption spectra and XRD patterns to the chemical synthesized K 2FeO 4 but different crystal morphologies.

One-step electrochemical synthesis of ZnO/Ru(dcbpy) 2(NCS) 2 hybrid thin films and their photoelectrochemical properties

Hybrid thin films of crystalline zinc oxide (ZnO) and Ru(dcbpy) 2(NCS) 2 (dcbpy=4,4′-dicarboxy-2,2′-bipyridine) have been synthesized by one-step cathodic electrodeposition from oxygen-saturated aqueous solutions containing zinc chloride and the Ru complex. While the pure ZnO thin films are oriented with the c-axis perpendicular to the substrate, the ZnO crystallites in the hybrid thin films are oriented with the c-axis parallel to the substrate as a consequence of the adsorption of the Ru complex onto the growing surface of ZnO. Thin hybrid films (up to about 0.5 μm) consist of grains with approximately 300 nm diameter, which are composed of ZnO crystallites of approximately 20 nm. For thicker films, the formation of an overlayer in a totally different morphology has been observed. The hybrid thin films have a composition of ZnO:Ru(dcbpy) 2(NCS) 2=30:1 in molar ratio, corresponding to a volume ratio of ZnO:Ru(dcbpy) 2(NCS) 2=1:1.7, indicating a very high amount of the Ru complex in the film. The loaded Ru complex can be mostly extracted by dipping the film in a dilute alkaline solution, indicating the porous nature of the film and the presence of the dye mainly on the surface of ZnO. The hybrid thin film electrodes exhibit sensitized photoanodic currents upon white light illumination in organic electrolyte solutions containing iodide which are analyzed in terms of wavelength dependence, I–V characteristics and by time-resolved photocurrent measurements. The thinner films performed considerably better than the thicker films in which dye aggregation seemed to decrease the electron injection efficiency.

A one-step electrochemical synthesis of polyaniline–polypyrrole composite coatings on carbon fibers

Polyaniline–polypyrrole composite coatings were formed on carbon fibers by potentiostatic electrochemical polymerization. Electropolymerization was done by varying the applied potential and molar feed ratio of monomers. The dual nature of the composite coatings was deduced from the current–time ( I– t) curves traced during polymerization. I– t curves were also used to predict the mechanism of the formation of composite coatings. UV–vis absorption spectroscopy was used to study the electronic structure of the composite coatings.

Photoelectrochemical properties of ZnO/tetrasulfophthalocyanine hybrid thin films prepared by electrochemical self-assembly

Dye-loaded zinc oxide (ZnO) thin films prepared by a one-step electrochemical synthesis from aqueous mixtures of zinc nitrate and water soluble tetrasulfonated metallophthalocyanines (TSPcMt), in which Mt = Zn(II), Al(III)[OH] or Si(IV)[OH]2 , have been studied photoelectrochemically. Visible light absorbed in the TSPcMt led to the sensitization of ZnO. A significantly higher conversion efficiency was found for monomeric as compared to aggregated TSPcMt adsorbed on the ZnO surface. The highest photocurrents were observed for TSPcSi. This could be explained by a strong interaction of the TSPcSi with the ZnO, leading to a highly ordered growth of the ZnO/TSPcSi films with a large fraction of TSPcSi monomers adsorbed to the ZnO surface. The strong adsorption also leads to a more efficient electron injection from the TSPcSi monomers into the conduction band of ZnO as compared to other TSPcMt.

One-Step Electrochemical Synthesis of α-MnO[sub 2] and α⋅γ-MnO[sub 2] Compounds for Lithium Batteries

One-Step Electrochemical Synthesis of α-MnO[sub 2] and α⋅γ-MnO[sub 2] Compounds for Lithium Batteries

Photoelectrochemical sensitisation of ZnO–tetrasulfophthalocyaninatozinc composites prepared by electrochemical self-assembly

Electrodes prepared by a one-step electrochemical synthesis of a dye-loaded ZnO thin film from an aqueous mixture of zinc nitrate and a water soluble phthalocyanine, 2,9,16,23-tetrasulfophthalocyaninatozinc(II) (TSPcZn) have been studied. Homogeneously blue transparent particulate thin films were formed. Monomeric or aggregated TSPcZn species could be obtained dependent on the deposition conditions. Visible light absorbed in TSPcZn led to sensitisation of ZnO. Negative shifts of the rest potential and anodic photocurrents were obtained in contact with an iodide-containing electrolyte in accordance with the n-type conduction of ZnO. Time-resolved measurements indicated charging and discharging of surface states, allowing discussion of the alignment of energy levels in the contact as well as of charge transfer and recombination in the cases of monomeric or aggregated TSPcZn. Electrons were injected into ZnO from the first excited singlet state of TSPcZn. Monomeric TSPcZn showed a considerably larger quantum efficiency in sensitisation of ZnO, whereas a larger rate of charge transfer to the electrolyte was derived for the aggregated form.