Indium-decorated Pd nanocubes degrade nitrate anions rapidly

Indium-decorated palladium nanoparticles (In-on-PdNPs) are active for room-temperature catalytic reduction of aqueous nitrate, where the active sites are metallic In atoms on the Pd surface. The PdNPs are pseudo-spherical in shape, and it is unclear if their faceted nature plays a role in nitrate reduction. We synthesized different-sized, cube-shaped NPs with differing In coverages (sc%), and studied the resultant In-on-Pd-nanocubes (NCs) for nitrate reduction. The NCs exhibited volcano-shape activity dependence on In sc%, with peak activity around 65–75 sc%. When rate constants were normalized to undercoordinated atoms (at edge + corners), the NCs exhibited near-identical maximum activity (20×-higher than In-on-PdNPs) at ρIn/Pd edge+corner ∼0.5 (∼5 In atoms per 10 edge and corner atoms). NCs with a higher In edge + corner density (ρIn/Pd edge+corner ∼1.5) were less active but did not generate NH4+ at nitrate conversions tested up to 36 %. Edge-decorated cubes may be the structural basis of improved bimetallic catalytic denitrification of water

Indium-decorated Pd nanocubes degrade nitrate anions rapidly

Indium-decorated palladium nanoparticles (In-on-PdNPs) are active for room-temperature catalytic reduction of aqueous nitrate, where the active sites are metallic In atoms on the Pd surface. The PdNPs are pseudo-spherical in shape, and it is unclear if their faceted nature plays a role in nitrate reduction. We synthesized different-sized, cube-shaped NPs with differing In coverages (sc%), and studied the resultant In-on-Pd-nanocubes (NCs) for nitrate reduction. The NCs exhibited volcano-shape activity dependence on In sc%, with peak activity around 65-75 sc%. When rate constants were normalized to undercoordinated atoms (at edge+corners), the NCs exhibited near-identical maximum activity (20×-higher than In-on-PdNPs) at ρIn/Pd edge+corner ~0.5 (~5 In atoms per 10 edge and corner atoms). NCs with a higher In edge+corner density (ρIn/Pd edge+corner ~1.5) were less active but did not generate NH4+ at nitrate conversions tested up to 36%. Edge-decorated cubes may be the structural basis of improved bimetallic catalytic denitrification of water

Synthesis and Catalytic Properties of Silver Nanoparticle–Linear Polyethylene Imine Colloidal Systems

The excellent catalytic properties of colloidal metal nanoparticles (M-NPs), such as good selectivity, efficiency, and recyclability, have attracted great interest in academic and industrial research. However, new M-NP stabilizers/supports still need to be developed and their performance needs to be better understood. Herein, we report an approach for effectively combining a high-throughput method using linear polyethylene imine (LPEI) with <i>in situ</i> screening and multivariate optimization of the synthesis conditions to produce highly catalytically stable Ag-NPs. Selected Ag-NP/stabilizers were able to efficiently catalyze the <i>p</i>-nitrophenol (Nip) reduction by NaBH₄ in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (<i>k</i>₁) up to 1.66 s^–1 m^–2 L. A full kinetic analysis based on the Langmuir model indicates that the Nip molecules have a much stronger adsorption affinity than BH₄^– ions for the Ag-NP surface and all species are likely adsorbed and accommodated on the surface before they take part in any reaction

Mechanism of a Suzuki-Type Homocoupling Reaction Catalyzed by Palladium Nanocubes

The <i>trans</i>-2-phenylvinylboronic acid homocoupling reaction catalyzed by palladium nanocubes (Pd-NCs) was investigated by kinetics, spectroscopy, and poisoning experiments. The reaction was evidenced to be sensitive to the presence of the base, which acts synergistically with the substrate molecules and assists the leaching of Pd oxide (PdO_<i>x</i>) species to the reaction medium. This species catalyzes the homocoupling reaction through the formation of Pd–O_<i>x</i>–B­(OH)₂R pretransmetalation intermediates, via coordination with the vinylboronic acid molecules, involving an <i>oxo-palladium</i>-type interaction. The reaction rate was not enhanced by the saturation of the reaction medium with O₂, which is due to the oxidized nature of the Pd-NC surface

Screening the Formation of Silver Nanoparticles Using a New Reaction Kinetics Multivariate Analysis and Assessing Their Catalytic Activity in the Reduction of Nitroaromatic Compounds

On the basis of <i>in situ</i> selection utilizing a reaction kinetics parameter, a new and straightforward method for screening the formation of catalytically active silver-PVP nanoparticles is reported. The method utilizes a multivariate analysis for the optimization of the reactant concentrations in the synthesis of nanoparticles with an analytical response based on the ability of the nanoparticles formed to catalyze the reduction of <i>p</i>-nitrofenol <i>in situ</i>. The best synthetic conditions were selected, the nanoparticles fully characterized, and their catalytic properties with regard to the reduction of five nitroaromatic compounds, possessing different substituents at the <i>para</i> position, were determined. The kinetics analysis was based on the Langmuir–Hinshelwood semi-heterogeneous model. The results showed the greater ability of substrates to adsorb onto the nanoparticle surface compared with that of borohydride ions and that the substrates possessing an electron-withdrawing substituent are more catalytically favored. These differences are discussed in terms of substrate adsorption and of a linear free-energy relationship based on the Hammett plot

Catalytic Antioxidant Activity of Bis-Aniline-Derived Diselenides as GPx Mimics

Herein, we describe a simple and efficient route to access aniline-derived diselenides and evaluate their antioxidant/GPx-mimetic properties. The diselenides were obtained in good yields via ipso-substitution/reduction from the readily available 2-nitroaromatic halides (Cl, Br, I). These diselenides present GPx-mimetic properties, showing better antioxidant activity than the standard GPx-mimetic compounds, ebselen and diphenyl diselenide. DFT analysis demonstrated that the electronic properties of the substituents determine the charge delocalization and the partial charge on selenium, which correlate with the catalytic performances. The amino group concurs in the stabilization of the selenolate intermediate through a hydrogen bond with the selenium

Synthesis of Silver Glyconanoparticles from New Sugar-based amphiphiles and their catalytic application

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