title: Microbial engineering of nanoheterostructures: biological synthesis of a magnetically recoverable palladium nanocatalyst.
abstract: Precious metals supported on ferrimagnetic particles have a diverse range of uses in catalysis. However, fabrication using synthetic methods results in potentially high environmental and economic costs. Here we show a novel biotechnological route for the synthesis of a heterogeneous catalyst consisting of reactive palladium nanoparticles arrayed on a nanoscale biomagnetite support. The magnetic support was synthesized at ambient temperature by the Fe(III)-reducing bacterium, Geobacter sulfurreducens , and facilitated ease of recovery of the catalyst with superior performance due to reduced agglomeration (versus conventional colloidal Pd nanoparticles). Surface arrays of palladium nanoparticles were deposited on the nanomagnetite using a simple one-step method without the need to modify the biomineral surface, most likely due to an organic coating priming the surface for Pd adsorption, which was produced by the bacterial culture during the formation of the nanoparticles. A combination of EXAFS and XPS showed the Pd nanoparticles on the magnetite to be predominantly metallic in nature. The Pd(0)-biomagnetite was tested for catalytic activity in the Heck reaction coupling iodobenzene to ethyl acrylate or styrene. Rates of reaction were equal to or superior to those obtained with an equimolar amount of a commercial colloidal palladium catalyst, and near complete conversion to ethyl cinnamate or stilbene was achieved within 90 and 180 min, respectively.
authors.affiliation: School of Earth, Atmospheric & Environmental Sciences and Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester M13 9PL, UK. vicky.coker@manchester.ac.uk
authors.forename: Victoria S
authors.initials: VS
authors.lastname: Coker
authors.forename: James A
authors.initials: JA
authors.lastname: Bennett
authors.forename: Neil D
authors.initials: ND
authors.lastname: Telling
authors.forename: Torsten
authors.initials: T
authors.lastname: Henkel
authors.forename: John M
authors.initials: JM
authors.lastname: Charnock
authors.forename: Gerrit
authors.initials: G
authors.lastname: van der Laan
authors.forename: Richard A D
authors.initials: RA
authors.lastname: Pattrick
authors.forename: Carolyn I
authors.initials: CI
authors.lastname: Pearce
authors.forename: Richard S
authors.initials: RS
authors.lastname: Cutting
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Shannon
authors.forename: Joe
authors.initials: J
authors.lastname: Wood
authors.forename: Elke
authors.initials: E
authors.lastname: Arenholz
authors.forename: Ian C
authors.initials: IC
authors.lastname: Lyon
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Lloyd
mesh_terms: D000179:Acrylates / Q000737:chemistry; D002384:Catalysis; D002942:Circular Dichroism; D004738:Engineering / Q000379:methods*; D052203:Ferrosoferric Oxide / Q000737:chemistry / Q000378:metabolism; D045302:Geobacter / Q000378:metabolism*; D055772:Green Chemistry Technology; D007462:Iodobenzenes / Q000737:chemistry; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D020058:Styrene / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000179:Acrylates; D007462:Iodobenzenes; D020058:Styrene; D010165:Palladium; C040833:ethyl acrylate; C031905:iodobenzene; D052203:Ferrosoferric Oxide