Formation of Catalytic Silver Nanoparticles Supported on Branched Polyethyleneimine Derivatives

Abstract

A new and straightforward method for screening highly catalytically active silver nanoparticle-polymer composites derived from branched polyethyleneimine (PEI) is reported. The one-step systematic derivatization of the PEI scaffold with alkyl (butyl or octyl) and ethanolic groups led to a structural diversity correlated to the stabilization of silver nanoparticles and catalysis. Analysis of PEI derivative libraries identified a silver nanoparticle-polymer composite that was able to efficiently catalyze the p-nitrophenol reduction by NaBH(4) in water with a rate constant normalized to the surface area of the nanoparticles per unit volume (k(1)) of 0.57 s(-1) m(-2) L. Carried out in the presence of excess NaBH(4), the catalytic reaction was observed to follow pseudo-first-order kinetics and the apparent rate constant was linearly dependent on the total surface area of the silver nanoparticles (Ag-NPs), indicating that catalysis takes place on the surface of the nanoparticles. All reaction kinetics presented induction periods, which were dependent on the concentration of substrates, the total surface of the nanoparticles, and the polymer composition. All data indicated that this induction time is related to the resistance to substrate diffusion through the polymer support. Hydrophobic effects are also assumed to play an important role in the catalysis, through an increase in the local substrate concentration.

Natural reducing agents for electroless nanoparticle deposition: Mild synthesis of metal/carbon nanostructured microspheres

“…After normalization of k app by the molar concentration of silver in our suspensions (1.210 -5 M), we obtain a specific rate coefficient k = 122  16 s -1 M -1 , which is within the range of values observed for polymer-stabilized Ag nanoparticles (~25 nm) obtained at similar NaBH 4 concentrations [60], albeit much lower than values originally reported by Pradhan et al for bare Ag nanoparticles [55]. This suggests that, although we cannot exclude the presence of a partially blocking adsorbed layer, metallic surface sites at the carbon-supported Ag aggregates are highly available to catalyse heterogeneous reactions.…”

Polymer-coated palladium nanoparticle catalysts for Suzuki coupling reactions

“…The reduction to the p-aminophenolate ion is accompanied by two main absorbance variations: a decrease at 400 nm due to the consumption of the Nip reactant and an increase at 300 nm associated with the formation of the Amf product ( Figure 3). Because the amount of PdNPs added is very small, the absorption spectra of Nip are hardly affected by the presence of palladium nanoparticles [4].…”

“…The distinct catalytic activity of PdNPs in these reaction processes stems from their electronic properties and under-coordination of the surface atoms, which are sensitive to the particle size and shape, inter-particle distance and interaction mechanism. However, the high surface energy of PdNPs requires the use of stabilizers in order to prevent aggregation and loss of activity [1,4]. The surface chemistry of these nanoparticles is commonly modified and controlled using surfactants, peptides, ionic liquids, dendrimers or copolymers [5].…”

Palladium Nanoparticles within Core-Cross-Linked Polymer Gels for Suzuki Coupling Reactions: from Monomers to Ready-to-Use Catalysts in Two-Steps

“…Linear homopolymers (1-2) and linear diblock copolymers (3)(4) were considered in this investigation in order to clarify the relationship between macromolecular architecture (linear homopolymer, linear diblock copolymer and CCS copolymers) and catalytic activity of PdNPs. Sample 1 is commercially available, and sample 3 was synthesized following the procedures described by Liu et al 22 with adaptations, as described in detail elsewhere.…”

“…2 The usually high activity of PdNPs is attributed to electronic properties and under-coordination of surface atoms, which are sensitive to particle size and shape, and inter-particle distance and interaction mechanisms. 3 The high surface energy also renders PdNPs systems prone to aggregation and loss of activity [3][4][5] whenever the surface chemistry is not properly controlled. As a consequence, a great deal of effort has been put into the development of simple and effective strategies allowing for precise engineering of surface properties.…”