Xn:Harmful;
7440-05-3Relevant articles and documents
Kinetically controlled synthesis of triangular and hexagonal nanoplates of palladium and their SPR/SERS properties
Xiong, Yujie,McLellan, Joseph M.,Chen, Jingyi,Yin, Yadong,Li, Zhi-Yuan,Xia, Younan
, p. 17118 - 17127 (2005)
The rapid reduction of Na2PdCl4 by ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP) has recently been demonstrated as a convenient method of generating Pd cubooctahedra and twinned nanoparticles. Here we describe a new procedure where Pd triangular or hexagonal nanoplates could be selectively synthesized by manipulating the reduction kinetics of the polyol process. More specifically, the reduction rate was substantially reduced through the introduction of Fe(III) species and the O2/Cl- pair, two wet etchants for Pd(0). The etching power of the O 2/Cl- pair could be further enhanced by adding an acid to lower the pH of the reaction solution. Unlike the previously reported synthesis of Ag and Au nanoplates, light was found to have no indispensable role in the formation of Pd nanoplates. Both triangular and hexagonal nanoplates of Pd exhibited surface plasmon resonance (SPR) peaks in the visible region, and their positions matched with the results of discrete dipole approximation (DDA) calculation. Thanks to their sharp corners and edges, these Pd nanoplates could serve as active substrates for surface-enhanced Raman scattering (SERS).
Characterisation and microstructure of Pd and bimetallic Pd-Pt catalysts during methane oxidation
Persson, Katarina,Jansson, Kjell,Jaeras, Sven G.
, p. 401 - 414 (2007)
The catalytic oxidation of methane was studied over Pd/Al2O3 and Pd-Pt/Al2O3. It was found that the activity of Pd/Al2O3 gradually decreases with time at temperatures well below that of PdO decomposition. The opposite was observed for Pd-Pt/Al2O3, of which the activity decreases slightly with time. Morphological studies of the two catalysts showed major changes during operation. The palladium particles in Pd/Al2O3 are initially composed of smaller, randomly oriented crystals of both PdO and Pd. In oxidising atmospheres, the crystals become more oxidised and form larger crystals. The activity increase of Pd-Pt/Al2O3 is probably related to more PdO being formed during operation. The particles in Pd-Pt/Al2O3 are split into two different domains: one with PdO and the other likely consisting of an alloy between Pd and Pt. The alloy is initially rich in palladium, but the composition changes to a more equalmolar Pd-Pt structure during operation. The ejected Pd is oxidised into PdO, which is more active than its metallic phase. The amount of PdO formed depends on the oxidation time and temperature.
Transformations of β-hydroxo-substituted η3-allyl Pd complexes in neutral and weakly acidic solutions
Finashina,Kramareva,Evstigneeva,Flid,Belov
, p. 685 - 694 (2005)
The oxidation of some β-hydroxo-substituted η3-allyl Pd complexes based on the simplest 1,3-dienes is studied by the 1H and 13C NMR methods in neutral and weakly acidic methods. The composition of the reaction products is
Cross-coupling versus homocoupling in the reactions of dimethyl(N,N,N′,N′-tetramethylethanediamine)palladium with organic halides
De Graaf, Wim,Boersma, Jaap,Van Koten, Gerard
, p. 1479 - 1484 (1990)
Reaction of PdMe2(tmeda) (tmeda = N,N,N′,N′-tetramethylethanediamine) with benzyl and allyl bromide at 20°C affords the homocoupled product ethane and the organometallic complexes PdBr(η1-benzyl)(tmeda) and [Pd(η3-allyl)(tmeda)]Br, respectively. The reaction of PdMe2(tmeda) with acetyl chloride did not give the acetyl complex PdCl(COMe)(tmeda). Instead, the cross-coupled product acetone and the organometallic product PdClMe(tmeda) were obtained. Acetyl complexes PdX(COMe) (tmeda) were easily obtained by reaction of PdXMe(tmeda) with carbon monoxide at ambient temperature and pressure. The reaction of PdMe2(tmeda) with ethyl iodide is not selective and gives a 3:2 mixture of PdIMe(tmeda) and PdIEt(tmeda) together with a 3:2 mixture of propane and ethane. At 0°C, the reaction of PdMe2(tmeda) with benzyl bromide and the reaction of PdMe(benzyl)(tmeda) with methyl bromide both afford the palladium(IV) species a-benzyl-b-bromo-cd-dimethyl-ef-(tmeda)palladium(IV) (4a), in which the benzyl group and the bromine atom are in a cis position. 1H NMR spectroscopy in acetone-d6 at 0°C shows that in the reaction of the platinum(IV) complex PtMe2(tmeda) with benzyl bromide a trans oxidative-addition product, a-benzyl-f-bromo-bc-dimethyl-de-(tmeda)platinum(IV) (8a), is formed initially and that this complex rapidly isomerizes to a-benzyl-b-bromo-cd-dimethyl-ef-(tmeda)platinum(IV) (8b). We believe that similar addition/isomerization sequences occur in the reactions leading to 4a. The configuration of the thermodynamically stable palladium(IV) and platinum(IV) cis oxidative-addition products (4a and 8b) seems to be controlled by steric interaction between the benzyl group and the tmeda ligand.
Energetic and entropic contributions to self-assembly of binary nanocrystal superlattices: Temperature as the structure-directing factor
Bodnarchuk, Maryna I.,Kovalenko, Maksym V.,Heiss, Wolfgang,Talapin, Dmitri V.
, p. 11967 - 11977 (2010)
We studied the effect of temperature on self-assembly of monodisperse colloidal nanocrystals into single-component and binary superlattices. Temperature, which serves as a weighting factor for the internal energy (U) and entropy (S) contributions to the Helmholtz free energy F = U - TS, allows tailoring relative weights of the interparticle interactions and free-volume entropy during the formation of nanocrystal superlattices. Temperature also provides a convenient tool for directing self-assembly of nanocrystals toward desired superlattice structures. We found that temperature strongly affects the structures of binary superlattices self-assembled from the mixtures of CdSe + PbS nanocrystals and PbSe + Pd nanocrystals. In the former case, small Hamaker constants for CdSe and PbS nanocrystals led to a relatively simple phase diagram, including only high-density NaZn13-, AlB2-, and NaCl-type binary superlattices. In contrast, binary superlattices self-assembled at different temperatures from PbSe and Pd nanocrystals showed a number of low-density complex phases stabilized by strong local van der Waals interactions between Pd nanocrystals. The structural diversity of nanoparticle superlattices is shown to be a result of the cooperative effect of the entropy-driven crystallization and the interparticle interactions. Both ΔU and TΔS terms associated with the superlattice formation should be of the same order of magnitude, with |ΔU| |TΔS| for the PbSe and Pd nanocrystals.
Formation of palladium nanoparticles in olefin oxidation with iron(III) aqua ions in the presence of the Pd/ZrO2/SO4 metallic catalyst
Potekhin,Matsura
, p. 650 - 655 (2006)
The reactions of the Pd/ZrO2/SO4-catalyzed oxidation of ethylene, propene, and but-1-ene in a 0.1-1.5 M solution of perchloric acid with iron(III) aqua ions to carbonyl compounds, viz., acetaldehyde, acetone, and methyl ethyl ketone, respectively, were studied. The formation of palladium nanoparticles (5 nm) in solution on contact of the initial heterogeneous Pd/ZrO2/SO4 catalyst with perchloric acid was proved by transmission electron microscopy. The palladium nanoparticles are assumed to play the key role in olefin oxidation with the iron(III) aqua ions.
Recovery of palladium from spent solutions for manufacture of catalysts
Belobaba,Maslii,Medvedev
, p. 1952 - 1956 (2010)
Palladium recovery from [Pd(NH3)4]Cl2 solutions (concentration in terms of the metal 1 g l-1) with flow-through porous electrodes was studied. The conditions of effective electrochemical recovery of Pd were found. Various porous cathodes were compared.
Hydrogen sorption in Pd monolayers in alkaline solution
Martin,Lasia
, p. 5292 - 5299 (2009)
Hydrogen adsorption/absorption at palladium monolayers (ML) deposited on monocrystalline Au(1 1 1) electrode was studied in 0.1 M NaOH solution. H charge isotherms demonstrated that adsorption started at potentials more positive than at thicker nanometric
Mechanism of the reaction between the aqua complexes of palladium(II) and iron(II) in a solution of HClO4
Potekhin,Matsura,Solov'eva,Potekhin
, p. 381 - 384 (2004)
The kinetics of the reaction of an aqua complex of iron(II) with a tetraaqua complex of palladium(II) in a perchloric acid solution was studied over the temperature range 2055°C, and a reaction mechanism was proposed. It was found that the reaction is autocatalytic, and it occurs by a two-step one-electron transfer mechanism with the formation of iron(III) and palladium black. Based on the kinetic data, the nature of the autocatalysis in the test reaction was hypothesized.
Electroless Deposition of Palladium at Bare and Templated Liquid/Liquid Interfaces
Dryfe, Robert A. W.,Simm, Andrew O.,Kralj, Brett
, p. 13014 - 13015 (2003)
A simple, electroless approach to metallize the liquid/liquid interface is reported. The method is illustrated with the deposition of Pd at the bare water/1,2-dichloroethane interface, and for the templated deposition of Pd within the 100 nm diameter pores of γ-alumina membranes. Copyright
