Electrocatalytic Detection of Amitrole on the Multi-Walled Carbon Nanotube – Iron (II) tetra-aminophthalocyanine Platform

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Electrochemical behaviour of thiol-derivatised zinc (II) phthalocyanine complexes and their self-immobilised films at gold electrodes

Electrochemical properties of novel, peripherally substituted zinc phthalocyanine complex, octa(4-methylphenylthio-) phthalocyaninatozinc(II) [ZnPc(SC6H4CH3)8] (1a) in DMF solution are presented. This complex showed five quasi-reversible/reversible, diffusion-controlled redox couples. Solution voltammetry of 1a showed little contrast with that of its alkythiol-derivative, octabutylthiophthalocyaninatozinc(II) [ZnPc(SC4H9)8] (1b) in that both thiol-substituents tend to show electron-withdrawing influence on the phthalocyanine ligands; complex 1a showing easier reduction and more difficult to oxidation when compared to 1b and other alkyl derivatives. The voltammetric features of the solid ultrathin films of 1a and 1b, immobilized on gold electrodes via the self-assembling technique, are also presented. Interestingly, the self-assembled films are stable and reproducible and provide good suppression to the following Faradaic processes; gold surface oxidation, solution ion species and underpotential deposition (UPD) of copper

Synthesis, spectroscopy and photochemistry of octasubstituted thiol-derivatized phthalocyaninatozinc (II) complexes

Synthesis, spectroscopic and photochemical characterization of phenylthiol-derivatized zinc phthalocyanine complex: 2,3,9,10,16,17,23,24-octa(4-methylphenylthio-)phthalocyaninatozinc(II) [ZnPc(SC6H4CH3)8] (3a) and its alkanethiol derivative, 2,3,9,10,16,17,23,24-octabutylthiophthalocyaninatozinc(II) [ZnPc(SC4H9)8] (3b) are described. Spectroscopic analyses show that 3a has a higher aggregation tendency than 3b in organic solvents. Photochemical studies indicate that 3b is more photostable and more efficient at singlet oxygen generation than 3a

Surface electrochemistry of iron phthalocyanine axially ligated to 4-mercaptopyridine self-assembled monolayers at gold electrode

Surface electrochemical behaviour of a self-immobilised iron phthalocyanine (FePc) ultrathin film, via axial ligation reaction, onto a preformed 4-mercaptopyridine self-assembled monolayer on gold electrode has been described. Electrochemical evidence for the sensor clearly suggested surface-confined, flat “umbrella”-oriented and densely-packed monolayer film structure. The proposed electrochemical sensor exhibited good catalytic activity towards the oxidation of thiocyanate in pH 4.0 medium over a linear range of three decades of concentration (ca. 10−6–10−3 mol dm−3) with a detection limit in the order of ∼10−7 mol dm−3. The sensor exhibited useful potential for the analysis of thiocyanate in human urine and saliva samples. The advantageous properties of this type of electrode as a sensor for thiocyanate lie in its ease of fabrication, excellent catalytic activity, stability, sensitivity and simplicity

Electrochemical properties of surface-confined films of single-walled carbon nanotubes functionalised with cobalt(II)tetra-aminophthalocyanine : electrocatalysis of sulfhydryl degradation products of V-type nerve agents

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Electrocatalytic oxidation and detection of hydrazine at gold electrode modified with iron phthalocyanine complex linked to mercaptopyridine self-assembled monolayer

Electrocatalytic oxidation and detection of hydrazine in pH 7.0 conditions were studied by using gold electrode modified with self-assembled monolayer (SAM) films of iron phthalocyanine (FePc) complex axially ligated to a preformed 4-mercaptopyridine SAMs. The anodic oxidation of hydrazine in neutral pH conditions with FePc-linked-mercaptopyridine-SAM-modified gold electrode occurred at low overpotential (0.35 V versus Ag|AgCl) and the treatment of the voltammetric data showed that it was a pure diffusion-controlled reaction with the involvement of one electron in the rate-determining step. The mechanism for the interaction of hydrazine with the FePc-SAM is proposed to involve the Fe(III)Pc/Fe(II)Pc redox process. Using cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV), hydrazine was detected over a linear concentration range of 1.3 × 10−5 to 9.2 × 10−5 mol/L with low limits of detection (ca. 5 and 11 μM for OSWV and CV, respectively). At concentrations higher than 1.2 × 10−4 mol/L the anodic peak potential shifted to 0.40 V (versus Ag|AgCl), and this was interpreted to be due to kinetic limitations resulting from the saturation of hydrazine and its oxidation products onto the redox-active monolayer film. This type of metallophthalocyanine-SAM-based electrode is a highly promising electrochemical sensor given its ease of fabrication, good catalytic activity, stability, sensitivity and simplicity

Comparative electrochemistry and electrocatalytic activities of cobalt, iron and manganese phthalocyanine complexes axially co-ordinated to mercaptopyridine self-assembled monolayer at gold electrodes

Comparative surface electrochemistry and electrocatalytic properties of solid ultrathin monolayer films of metallophthalocyanine (MPc) complexes of cobalt (CoPc), iron (FePc) and manganese (MnPc) self-immobilised, via axial ligation reaction, onto preformed 4-mercaptopyridine self-assembled monolayers (SAMs) on gold electrodes have been described. Surface electrochemical parameters of the modified electrodes showed that these MPc-SAMs are densely packed with flat orientations. The electrochemical, electrocatalytic and stability properties of these MPc complexes follow this order: FePc > MnPc > CoPc. This finding is remarkable as it suggests that the success of using this method of self-assembling of MPc onto gold electrode is largely dependent on the bond distance between the pyridine linker and the central metal of the MPc; the shorter the distance, the faster the co-ordination and the better the electrocatalytic properties towards L-cysteine and thiocyanate. Thus, the superiority of FePc-based SAM over those of the MnPc and CoPc, has been proposed to be the result of the more favorable axial co-ordination properties of FePc with pyridine (i.e. shorter Fe–N(pyridine) bond length

Enhanced methanol oxidation and oxygen reduction reactions on palladium-decorated FeCo@Fe/C Core-shell nanocatalysts in alkaline medium

Palladium based nano-alloys are well known for their unique electrocatalytic properties. In this work, a palladium-decorated FeCo@Fe/C core–shell nanocatalyst has been prepared by a new method called microwave-induced top-down nanostructuring and decoration (MITNAD). This simple, yet efficient technique, resulted in the generation of sub-10 nm sized FeCo@Fe@Pd nanocatalysts (mainly 3–5 nm) from a micron-sized (0.21–1.5 mm) FeCo@Fe/C. The electrocatalytic activities of the core–shell nanocatalysts were explored for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline medium. A negative shift of 300 mV in the onset potential for MOR was observed, with a current thrice that of the Pd/C catalysts. A very low resistance to electron transfer (Rct) was observed while the ratio of forward-to-backward oxidation current (If/Ib) was doubled. The overpotential of ORR was significantly reduced with a positive shift of about 250 mV and twice the reduction current density was observed in comparison with Pd/C nanocatalysts with the same mass loading. The kinetic parameters (in terms of the Tafel slope (b) = 59.7 mV dec 1 (Temkin isotherm) and high exchange current density ( jo) = 1.26 10 2 mA cm 2) provide insights into the favorable electrocatalytic performance of the catalysts in ORR in alkaline media. Importantly, the core–shell nanocatalyst exhibited excellent resistance to possible methanol cross-over during ORR, which shows excellent promise for application in direct alkaline alcohol fuel cells (DAAFCs).http://www.rsc.org/pccpam201

Electropolymerizable iron (III) and cobalt (II) dicyanophenoxy tetraphenylporphyrin complexes

Solution and solid phase electrochemical features of 5-[4-(3,4-dicyanophenoxy)phenyl],10,15,20-triphenylporphyrin complexes of iron(III) (FeCNOTPP(Cl)) and cobalt(II) (CoCNOTPP) have been described. These novel asymmetric dicyanophenoxy-derivatised cobalt and iron porphyrin complexes were electropolymerised onto glassy carbon electrodes, which in aqueous solutions, gave surface concentrations (ca. 10−10 mol cm−2) typical of monolayer coverages. The films also exhibited excellent stability and electrocatalysis towards the direct detection of important analytes as nitrite, nitric oxide, and hydrogen peroxide in aqueous solutions

Hydrogen peroxide oxidation of 2-chlorophenol and 2, 4, 5-trichlorophenol catalyzed by monomeric and aggregated cobalt tetrasulfophthalocyanine

Cobalt tetrasulfophthalocyanine (CoTSPc) was used to catalyze the oxidation of 2-chlorophenol (2-CP) and 2,4,5-trichlorophenol (TCP) using hydrogen peroxide (H2O2) as the oxidant. This CoTSPc catalyzed hydrogen peroxide oxidation of chlorophenols resulted in the formation of different types of oxidation products depending on the solvent conditions. In water/methanol conditions (where CoTSPc is mainly monomeric, and unionized forms of the phenols), phenol and hydroquinone were the main oxidation products, while in phosphate buffer solutions (pH 7 and 10 for TCP and 2-CP, respectively, where CoTSPc is mainly aggregated, and ionized forms of the phenols), benzoquinone was the main product. In contrast to CoTSPc, other MTSPc complexes studied (AlTSPc, CuTSPc and NiTSPc) exhibited no detectable catalytic effect on the oxidation of chlorophenols under the experimental conditions employed, thus proving the effect of the central metal ions on efficient catalysis of chlorophenol. Reaction pathways are proposed based on the relative time of oxidation products formation