Preparation of Well-Defined Dendrimer Encapsulated Ruthenium Nanoparticles and Their Evaluation in the Reduction of 4-Nitrophenol According to the Langmuir–Hinshelwood Approach

Abstract

This study discusses the preparation of various sized dendrimer encapsulated ruthenium nanoparticles (RuDEN) with the use of the generation 4 (G4), generation 5 (G5), and generation 6 (G6) hydroxyl-terminated poly(amidoamine) (PAMAM-OH) dendrimers as templating agents. The size of the nanoparticles ranges from 1.1 to 2.2 nm. These catalysts were fully characterized using UV/vis spectrophotometry, infrared (IR) spectroscopy, and transmission electron microscopy (TEM). The RuDEN catalysts were evaluated in the reduction of 4-nitrophenol (4NP) in the presence of sodium borohydride (BH4(-)) for various concentrations of either. The kinetic data obtained were modeled to the Langmuir-Hinshelwood equation. The model allows the relation of the apparent rate constant to the total surface area S of the nanoparticle, the kinetic constant k which is related to the rate-determining step, and the adsorption constants K(4NP) and K(BH4) for 4NP and borohydride, respectively. These parameters were calculated for each of the RuDENs, proving the Langmuir-Hinshelwood model to be suitable for the kinetic evaluation of RuDENs in the catalytic reduction of 4NP.

Kinetic studies of catalytic reduction of 4-nitrophenol with NaBH4 by means of Au nanoparticles dispersed in a conducting polymer matrix

“…The zeroorder kinetics of 4-NPh reduction was also reported for catalytic process performed on Fe@Au nanoparticles supported on graphene oxide (with k = 8.21 × 10 −6 mol dm −3 min −1 ) [2] and on Au nanoparticles grown on calcium alginate beads (k in the range 1.4-2 × 10 −6 mol dm −3 min −1 ) [20]. Since these results are in contradiction with other literature data indicating the first-order kinetics [19,31,[33][34][35][36][37][38], we performed the Fig. 3b).…”

“…The catalytic reduction of 4-NPh on Au nanoparticles in the concentration range up to 2.4× 10 −4 M is usually reported in the literature as the pseudo-first-order reaction with respect to 4-NPh, at excessive concentration of NaBH 4 [19,31,[33][34][35][36][37][38]. If so, the experimental data should follow a linear dependence of ln(c/c o ) on time.…”

The preparation of well-defined dendrimer-encapsulated palladium and platinum nanoparticles and their catalytic evaluation in the oxidation of morin

“…The Freundlich exponents n and m which describe the heterogeneity of the catalyst are expected to be unity for a perfectly homogenous surface. However from the values of n and m obtained in our fitting (ca 0.8-1.0), it can be concluded that there is some surface heterogeneities of our catalysts, an observation reported for ruthenium dendrimerencapsulated nanoparticles [43] as well as for gold nanoparticles [44].…”

Kinetics of the catalytic oxidation of morin on γ-Al 2 O 3 supported gold nanoparticles and determination of gold nanoparticles surface area and sizes by quantitative ligand adsorption

“…The analysis of the kinetic data was performed in terms of the Langmuir-Hinshelwood model [60,61], in which both reactants must be adsorbed on the surface of the nanoparticles. Similar approach has been used in many reactions [54,62,63]. A schematic representation of this model is displayed in Fig.…”