First evidence that D. ferrophilus IS5 forms surface attached Pd(0) nanoparticles.

Unlike D. desulfuricans, IS5 rapidly forms Pd(0) coated microbial nanowires.

Nanowire production leads to enhanced attachment of IS5 to steel surfaces.

Desulfovibrio spp. can form 3D mm-sized bacteria/Pd hybrid microstructures.

Desulfovibrio spp. can form 2D nanosheets of Pd metal up to several cm in length.

A range of Desulfovibrio spp. can reduce metal ions to form metallic nanoparticles that remain attached to their surfaces. The bioreduction of palladium (Pd) has been given considerable attention due to its extensive use in areas of catalysis and electronics and other technological domains. In this study we report, for the first time, evidence for Pd(II) reduction by the highly corrosive Desulfovibrio ferrophilus IS5 strain to form surface attached Pd nanoparticles, as well as rapid formation of Pd(0) coated microbial nanowires. These filaments reached up to 8 µm in length and led to the formation of a tightly bound group of interconnected cells with enhanced ability to attach to a low carbon steel surface. Moreover, when supplied with high concentrations of Pd (≥ 100 mmol Pd(II) g−1 dry cells), both Desulfovibrio desulfuricans and D. ferrophilus IS5 formed bacteria/Pd hybrid porous microstructures comprising millions of cells. These three-dimensional structures reached up to 3 mm in diameter with a dose of 1200 mmol Pd(II) g−1 dry cells. Under suitable hydrodynamic conditions during reduction, two-dimensional nanosheets of Pd metal were formed that were up to several cm in length. Lower dosing of Pd(II) for promoting rapid synthesis of metal coated nanowires and enhanced attachment of cells onto metal surfaces could improve the efficiency of various biotechnological applications such as microbial fuel cells. Formation of biologically stimulated Pd microstructures could lead to a novel way to produce metal scaffolds or nanosheets for a wide variety of applications.

Brunauer-Emmett-Teller

Biologically produced Palladium

Inductively Coupled Plasma Triple Quadrupole Mass Spectrometer

Energy Dispersive X-ray

Powder X-ray Diffraction

Sulfate Reducing Bacteria

Scanning Electron Microscope

Thermo Gravimetric Analysis

Desulfovibrio ferrophilus IS5

Desulfovibrio desulfuricans

Palladium reduction

Palladium microstructures

Palladium nanosheets

Microbial nanowires

© 2022 Published by Elsevier B.V.