Nano-electrochemical detection of hydrogen or protons using palladium nanoparticles: distinguishing surface and bulk hydrogen.

The benefits of using nanoparticle-modified electrodes are exemplified through the electrochemical detection of protons and/or hydrogen. It is shown that a palladium-nanoparticle-modified boron-doped diamond allows voltammetric information relating to the relative roles played by the surface and the bulk metal to be obtained for the proton-hydrogen system at palladium surfaces which is not accessible using palladium macroelectrodes or microelectrodes.     

Reversible sorption of hydrogen by colloidal palladium in aqueous solutions

Colloidal palladium was prepared by -irradiation or by H₂ reduction of Pd(NH₃)₄l₂ in aqueous solutions containing sodium polyacrylate as a stabilizer. The sots contain spherical particles 2–4 nm in diameter. Their optical spectra contain a band at 230 nm ( = 6.1 · 10³ L mol^–1 cm^–1) smoothly descending toward the visible range. The sots reversibly absorb chemically from 0.35 to 0.15 g-mol of H₂ per g-atom of Pd. The spectra of ultrafine metal particles saturated with molecular hydrogen exhibit an absorption band at 265 nm ( = 4.5 · 10³ L mol^–1 cm^–1). One-electron reduction of methylviologen by hydrogen is catalyzed by the colloidal palladium prepared.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 313–316, February, 1996.     

Photoresponsive polymers and block copolymers by molecular recognition based on multiple hydrogen bonds

A new methacrylate containing a 2,6‐diacylaminopyridine (DAP) group was synthesized and polymerized via RAFT polymerization to prepare homopolymethacrylates (PDAP) and diblock copolymers combined with a poly(methyl methacrylate) block (PMMA‐b‐PDAP). These polymers can be easily complexed with azobenzene chromophores having thymine (tAZO) or carboxylic groups with a dendritic structure (dAZO), which can form either three or two hydrogen bonds with the DAP groups, respectively. The supramolecular polymers were characterized by spectroscopic techniques, optical microscopy, TGA, and DSC. The supramolecular polymers and block copolymers with dAZO exhibited mesomorphic properties meanwhile with tAZO are amorphous materials. The response of the supramolecular polymers to irradiation with linearly polarized light was also investigated founding that stable optical anisotropy can be photoinduced in all the materials although higher values of birefringence and dichroism were obtained in polymers containing the dendrimeric chromophore dAZO. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3173–3184     

Synthesis and electropolymerization of EDOT modified 1,3-bis(5-methyl-2-thiazolylimino)isoindolinato palladium(II) complex for electrochemical detection of hydrogen peroxide

1,3-Bis(5-methyl-2-thiazolylimino) isoindoline derivative (EDOT-BTI) containing an electropolymerizable group is prepared using the Linstead method. According to this two-step method phthalonitrile derivative EDOT-Pht is converted to 1,3-diiminoisoindoline EDOT-DII first then EDOT-DII is reacted with 2-amino-5-methylthiazole in ethanol during 5 day reflux. Palladium(II) complex (EDOT-PdBTI) of EDOT-BTI is synthesized in benzene using [Pd(PhCN)₂Cl₂] as the palladium(II) precursor and triethylamine as auxiliary base. In order to show the H₂O₂ sensing properties of EDOT-PdBTI, electrochemical characterizations of EDOT-BTI and EDOT-PdBTI are performed and then modified glassy carbon electrode is constructed with electropolymerization of EDOT-PdBTI. GCE/PEDOT-PdBTI shows a wave at 0.215 V. With increasing H₂O₂ concentration, this wave shifts to ?0.075 V. A linear range is observed between 0.72 and 13.6 μmol dm^?3 with a limit of detection of 0.21 μmoldm^?3 and sensitivity of 0.0153 mV μmol^?1 dm^?3. These data illustrate possible use of the electrode as a potentiometric H₂O₂ sensor.     

Adsorption of hydrogen on palladium nanoparticle surfaces

The behaviors of hydrogen (H) adsorbed on the palladium (Pd) nanoparticles (NPs) are examined with the modified analytic embedded‐atom method potentials and MORSE potentials. We study the effects of particle size and H coverage, and compare their adsorption properties of nanoparticle's facets with that of flat surfaces. We simulate the Pd truncated octahedron NPs with atoms from 38 to 2406 and the coverage of adsorbed H up to 1.0 monolayer (ML). Site preferences, adsorption geometries, adsorption energies, and bond lengths of H? Pd are calculated. We have also calculated the potential energy surface (PES). It is clear that the H atom binding to particle facets is quite stronger than that of flat surfaces when the particle size is smaller than 3.2 nm. We have found a significant variation that adsorption energies ascend gradually with increasing the particle size or surface coverage of H, and the adsorption energy varies about 0.6 eV for (111) facet and 0.3 eV for (100) facet as the coverage up to 1.0 ML. Our results are in reasonable agreement with the experimental values and other calculations. Copyright © 2009 John Wiley & Sons, Ltd.     

Multifunctional fourfold interpenetrating diamondoid network: gas separation and fabrication of palladium nanoparticles

A fourfold interpenetrating diamondoid network, [{[Ni(cyclam)]2-(mtb)}(n)].8n H2O.4n DMF (1) (MTB=methanetetrabenzoate, DMF=dimethylformamide), has been assembled from [Ni(cyclam)][ClO4]2 (cyclam=1,4,8,11-tetraazacyclotetradecane) and methanetetrabenzoic acid (H4MTB) in DMF/H2O (7:3, v/v) in the presence of triethylamine (TEA). Despite the high-fold interpenetration, 1 generates 1D channels that are occupied by water and DMF guest molecules. Solid 1, after removal of guest molecules, exhibits selective gas adsorption behavior for H2, CO2, and O2 rather than N2 and CH4, suggesting possible applications in gas separation technologies. In addition, solid 1 can be applied in the fabrication of small Pd (2.0+/-0.6 nm) nanoparticles without any extra reducing or capping agent because a Ni II macrocyclic species incorporated in 1 reduces Pd II ions to Pd 0 on immersion of 1 in the solution of Pd(NO3)2.2H2O in MeCN at room temperature.     

3D amino-induced electroless plating: a powerful toolset for localized metallization on polymer substrates

The "3D amino-induced electroless plating" (3D-AIEP) process is an easy and cost-effective way to produce metallic patterns onto flexible polymer substrates with a micrometric resolution and based on the direct printing of the mask with a commercial printer. Its effectiveness is based on the covalent grafting onto substrates of a 3D polymer layer which presents the ability to entrap Pd species. Therefore, this activated Pd-loaded and 3D polymer layer acts both as a seed layer for electroless metal growth and as an interdigital layer for enhanced mechanical properties of the metallic patterns. Consequently, flexible and transparent poly(ethylene terephtalate) (PET) sheets were selectively metalized with nickel or copper patterns. The electrical properties of the obtained metallic patterns were also studied.     

PEDOT films: multifunctional membranes for electrochemical ion sensing

Properties of electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) films were studied from the point of view of direct use as ion-sensing membranes in potentiometric or amperometric sensors. Stable and reproducible potentiometric characteristics were obtained for PEDOT doped by poly(4-styrenesulfonate) ions, PEDOT(PSS) (cationic characteristics), and PEDOT doped by hexacyanoferrate(II) anions, PEDOT(HCF) (anionic characteristics). As shown by voltammetric and EDAX results, the anion exchange properties of the latter polymer result from gradual replacement of HCF ions by Cl^– anions from solution. The zero-current potentiometric detection limit of PEDOT(PSS), equal to 3×10^–6 M, can be shifted to 7×10^–7 M by polarization using a cathodic current density of 3×10^–7 A cm^–2. PEDOT films doped by Cl^– or PSS^– ions can be used as membranes for sensing anions or cations, respectively, under pulse amperometric conditions, within the range from 10^–4 to 1 M, comparable with that accessible by zero-current potentiometry. Dissolved oxygen (redox interferent of low charge transfer rate) exerts a minor influence on the slope of the potentiometric and amperometric characteristics of PEDOT films. Although the presence of redox reactants characterized by a high rate of charge transfer [Fe(CN)₆ ^3–/4–] results in the disappearance of the potential dependence on KCl concentration, this disadvantageous effect is much less significant under pulse amperometric conditions.Contribution to the 3rd Baltic Conference on Electrochemistry, GDASK-SOBIESZEWO, 23–26 April 2003. Dedicated to the memory of Harry B. Mark, Jr. (February 28, 1934–March 3rd, 2003)     

Synthesis,spectral and thermal studies on pyrazolatebridged palladium(II) coordination polymers

Synthesis, spectroscopic characterization and thermal behavior of pyrazolate-bridged palladium complexes [Pd(μ-Pz)₂]_n (1), [Pd(μ-mPz)₂]_n (2), [Pd(μ-dmPz)₂]_n (3), [Pd(μ-IPz)₂]_n (4) {pyrazolate (Pz^–), 4-methylpyrazolate (mPz^–), 3,5-dimethylpyrazolate (dmPz^–), 4-iodopyrazolate (IPz^–)} have been described in this work. The exobidentate coordination mode of pyrazolato ligands in 1–4 was inferred on basis of IR spectroscopic evidences. TG investigations indicated that the introduction of substituents at the 4 position in the pyrazolyl moiety into coordination polymers do not affect significantly their thermal stability, whereas at the 3 and 5 position reduced the stability of the main chain. Metal palladium was the final product of the thermal decompositions, which was identified by X-ray powder diffraction.     

Experimental studies on the hydrogen isotope recovery using low-pressure palladium membrane diffuser

In this paper, we introduce a set of low-pressure palladium membrane diffuser designed to recover hydrogen isotopes from inert mixture gases. Several gaseous mixtures (D₂/Ar and D₂/He) with different deuterium concentration have been used for cleanup test of the low-pressure palladium membrane diffuser at 723 K. Effect of the composition of feed gas on the pressure of permeate side has been observed by gas chromatography (GC) and pressure sensor. With the feed flow rate of the mixture gases increasing, the D₂ permeate pressure is increasing as well. Decontamination factor (DF) of more than 1000 and recovery efficiency greater than 99.9% have been obtained by controlling the feed gas flow rate. The same palladium membrane diffuser was used to process helium-3 gas with more than 10% hydrogen isotope and about 0.3% tritium gas. The pure helium-3 (above 99.4%) with low content of hydrogen isotopes (about 0.084%) has been obtained. Recovery efficiency of all hydrogen isotopes is 99.5% above.     

Molecularly imprinted conducting polymer based electrochemical sensor for detection of atrazine

An original electrochemical sensor based on molecularly imprinted conducting polymer (MICP) is developed, which enables the recognition of a small pesticide target molecule, atrazine. The conjugated MICP, poly(3,4-ethylenedioxythiophene-co-thiophene-acetic acid), has been electrochemically synthesized onto a platinum electrode following two steps: (i) polymerization of comonomers in the presence of atrazine, already associated to the acetic acid substituent through hydrogen bonding, and (ii) removal of atrazine from the resulting polymer, which leaves the acetic acid substituents open for association with atrazine. The obtained sensing MICP is highly specific towards newly added atrazine and the recognition can be quantitatively analyzed by the variation of the cyclic voltammogram of MICP. The developed sensor shows remarkable properties: selectivity towards triazinic family, large range of detection (10⁻⁹ mol L⁻¹ to 1.5 × 10⁻² mol L⁻¹ in atrazine) and low detection threshold (10⁻⁷ mol L⁻¹).     

Three-dimensional triazenido layers attained through classical and non-classical hydrogen interactions and its coordination to palladium under prolific occurrence of bifurcated hydrogen bonding

The new ligand 1,3-bis(3-methoxy-4-methylbenzoate) triazene (1, bmmbt), and the already known ligand 1,3-bis(4-acetylphenyl)triazene (bapht), yield the two new palladium(II) complexes [(bmmbt)Pd(PPh₃)₂Cl]·DMSO (2) and [(bapht)Pd(PPh₃)₂Cl] (3) (Ph = phenyl; DMSO = dimethylsulfoxide). Compound 1 shows the existence of more than one interaction promoting the coupling between the triazene chains. Other remarkable types of interactions in 1 are bifurcated hydrogen contacts and non-classical CH···π bonding. Complexes 2 and 3 present a planar geometry, supported also through bifurcated intramolecular Cl···H-C interactions, as well as the occurrence of trifurcated Cl···H-C intermolecular interactions.