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Catalytic activity of palladium and gold dendrimer-encapsulated nanoparticles for methylene blue reduction: A kinetic analysis

Paper ID Volume ID Publish Year Pages File Format Full-Text
39302 45817 2015 9 PDF Available
Title
Catalytic activity of palladium and gold dendrimer-encapsulated nanoparticles for methylene blue reduction: A kinetic analysis
Abstract

•Kinetic analysis of the reduction of MB at low temperatures using dendrimer encapsulated nanoparticles.•Analysis of the experimental kinetic data using the Langmuir–Hinshelwood model.•First report on the adsorption constants of MB, KMB on Pd and Au DENs as determined by the L–H model.•Thermodynamic parameters for the reduction of MB using Pd and Au DENs.

A kinetic analysis of the catalytic reduction of methylene blue (MB) by sodium borohydride (BH4−) using colloidal dendrimer-encapsulated palladium (Pd) and gold (Au) nanoparticles (PdDENs and AuDENs) is presented. The nanoparticles were prepared by the template method using generation 4 (G4) and generation 5 (G5) hydroxyl-terminated poly (amido)amine (PAMAM-OH) dendrimers for PdDENs and amine-terminated poly (amido)amine (PAMAM-NH2) for AuDENs in aqueous solution. The catalysts were characterized by UV/vis spectrophotometry and transmission electron microscopy (TEM). The sizes of the particles obtained ranged from 1.3 to 2.3 nm with volume normalized surface areas between 0.02 and 0.06 m2 L−1. The reduction of MB by BH4− was monitored by UV/vis spectrophotometry using the stopped-flow technique and the kinetic data obtained was modeled to the Langmuir–Hinshelwood mechanism. The apparent rate constant for the reduction is related to the surface area S of the nanoparticles, the adsorption constants of MB (KMB) and BH4−(KBH4−)(KBH4−) as well as to the kinetic constant k which is related to the rate-determining step of the reaction. The kinetic constant k was largest for PdDENs with the largest volume normalized surface area of 0.06 m2 L−1. KMB values were 10 times larger than those of KBH4−KBH4− in the case of PdDENs. The activation energy was lowest for the most catalytic active PdDENs at 34.5 ± 1.5 kJ mol−1 as compared to 71.3 ± 1.6 kJ mol−1, for the least active AuDEN catalyst.

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Keywords
Palladium; Gold; Dendrimer-encapsulated nanoparticles; Catalysis; Methylene blue; Kinetics
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Catalytic activity of palladium and gold dendrimer-encapsulated nanoparticles for methylene blue reduction: A kinetic analysis
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 495, 5 April 2015, Pages 63–71
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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Price after discount Only $4.95
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