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 in situ 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 p-nitrophenol (Nip) reduction by NaBH4 in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (k 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.

We report the catalytic activity evaluation of in situ grown Pd nanoparticles on the surface of superparamagnetic Fe3O4 particles coated with the natural polymer dextran, in the reduction of p-nitrophenol (Nip), in water, by sodium borohydride.

Per- and polyfluoroalkyl substances (PFASs) comprise a group of widespread and recalcitrant contaminants that are attracting increasing concern due to their persistence and adverse health effects. This study evaluated removal of one of the most prevalent PFAS, perfluorooctanoic acid (PFOA), in H2-based membrane catalyst-film reactors (H2-MCfRs) coated with palladium nanoparticles (Pd0NPs). Batch tests documented that Pd0NPs catalyzed hydrodefluorination of PFOA to partially fluorinated and nonfluorinated octanoic acids; the first-order rate constant for PFOA removal was 0.030 h–1, and a maximum defluorination rate was 16 μM/h in our bench-scale MCfR. Continuous-flow tests achieved stable long-term depletion of PFOA to below the EPA health advisory level (70 ng/L) for up to 70 days without catalyst loss or deactivation. Two distinct mechanisms for Pd0-based PFOA removal were identified based on insights from experimental results and density functional theory (DFT) calculations: (1) nonreactive chemisorption of PFOA in a perpendicular orientation on empty metallic surface sites and (2) reactive defluorination promoted by physiosorption of PFOA in a parallel orientation above surface sites populated with activated hydrogen atoms (Hads *). Pd0-based catalytic reduction chemistry and continuous-flow treatment may be broadly applicable to the ambient-temperature destruction of other PFAS compounds.

The trans-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 x ) species to the reaction medium. This species catalyzes the homocoupling reaction through the formation of Pd–O x –B­(OH)2R pretransmetalation intermediates, via coordination with the vinylboronic acid molecules, involving an oxo-palladium-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.

PFAAs (perfluorinated alkyl acids) have become a concern because of their widespread pollution and persistence. A previous study introduced a novel approach for removing and hydrodefluorinating perfluorooctanoic acid (PFOA) using palladium nanoparticles (Pd 0 NPs) in situ synthesized on H 2 -gas-transfer membranes. This work focuses on the products, pathways, and optimal catalyst conditions. Kinetic tests tracking PFOA removal, F − release, and hydrodefluorination intermediates documented that PFOA was hydrodefluorinated by a mixture of parallel and stepwise reactions on the Pd 0 NP surfaces. Slow desorption of defluorination products lowered the catalyst's activity for hydrodefluorination. Of the platinum group metals studied, Pd was overall superior to Pt, Rh, and Ru for hydrodefluorinating PFOA. pH had a strong influence on performance: PFOA was more strongly adsorbed at higher pH, but lower pH promoted defluorination. A membrane catalyst-film reactor (MCfR), containing an optimum loading of 1.2 g/m 2 Pd 0 for a total Pd amount of 22 mg, removed 3 mg/L PFOA during continuous flow for 90 days, and the removal flux was as high as 4 mg PFOA/m 2 /d at a steady state. The EPA health advisory level (70 ng/L) also was achieved over the 90 days with the influent PFOA at an environmentally relevant concentration of 500 ng/L. The results document a sustainable catalytic method for the detoxification of PFOA-contaminated water.

On the basis of in situ 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 p-nitrofenol in situ. 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 para 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.

Oligosaccharide-based amphiphiles were readily prepared by click chemistry from ω-azido-hexanoic or dodecanoic acids with propargyl-functionalized maltoheptaose or xyloglucanoligosaccharides. These amphiphilic compounds were used as capping/stabilizer agents in order to obtain highly stable catalytic silver glyconanoparticles (Ag-GNPs) through the in situ reduction of silver nitrate with NaBH4. With a view to long-term storage, the stabilization was optimized using a multivariate approach, and the nanoparticles were characterized by UV-vis, TEM, SAXS, and DLS. In order to explore the functionality of the Ag-GNPs in catalysis, a full kinetic analysis of the reduction of p-nitrophenol by NaBH4 in water and in water/ethanol mixtures was performed under semi-heterogeneous and quasi-homogeneous conditions. A pseudomonomolecular surface reaction was performed, and the kinetic data obtained were treated according to the Langmuir model. The Ag-GNPs were very active, and both substrates adsorbed onto the surface of the nanoparticles. For comparison purposes, the reaction was also performed in the presence of silver-sodium dodecanoate nanoparticles, which showed catalytic activity similar to that of the glyconanoparticles, supporting the choice of the carboxyl group as the stabilizing agent, although it provided much lower temporal stability. Finally, by combining kinetic and water/ethanol surface tension data it was possible to observe the effect of the addition of the less polar solvent (ethanol) to the reaction medium.

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.