Effect of Copper and Phosphate on the Biosynthesis of Palladium Nanoparticles by Shewanella oneidensis MR‐1

Abstract

The biosynthesis of metallic nanomaterials, especially noble metal nanomaterials, has attracted extensive attention due to the multifarious potential applications of these materials. In this study we have explored the effects of Cu(II) on Pd(II) removal, and of Cu(II) as well as phosphate on the morphologies and composition of biogenic nanoparticles (NPs) from aqueous Pd (II) systems by Shewanella oneidensis MR-1 (MR-1). Cu(II) causes a slight efficiency decrease of Pd(II) removal by MR-1, but a high removal efficiency of 89.8 % is still achieved, which contrasts sharply with the significant Cu(II) inhibition to other microbes. Without phosphate buffer in the medium, 5-nm PdNPs densely envelop MR-1 and accumulate significantly in the periplasm in the absence of Cu(II), while 4-nm PdNPs are evenly distributed in the periplasm, and the cellular surface is smooth in the presence of Cu(II). The following effect of Cu(II) on PdNP synthesis by MR-1 is therefore proposed: Cu(II) significantly affects PdNPs morphologies by inhibiting Pd(0) transfer across the outer membrane and PdNP crystal growth in the periplasm, but not the sorption of Pd(II). Phosphate addition only slightly increases Pd harvest but also precipitates Cu(II) and poses difficulties for the biosynthesis. The study highlights the effect of co-existing metals during the biosynthesis of metallic nanomaterials and offers new insight into the mechanism of PdNP formation and the electron transfer during Pd(II) reduction by MR-1.

Utilizing a divalent metal ion transporter to control biogenic nanoparticle synthesis

“…There are several naturally occurring biomolecules that facilitate nanoparticle formation (Venegas et al., 2017 ), including peptides and proteins that nucleate CdS and silver nanoparticles (Dameron et al., 1989 ; Klaus et al., 1999 ). The redox activity of many bacteria has also been implemented for metal reduction and subsequent nanoparticle formation (Chellamuthu et al., 2019 ; Dunleavy et al., 2016 ; Dundas et al., 2018 ; McFarlane et al., 2015 ; Zheng et al., 2020 ). In addition to these naturally occurring pathways, directed evolution has been used to identify peptide sequences capable of nucleating a variety of inorganic nanomaterials (Flynn et al., 2003 ; Krajina et al., 2018 ; Sweeney et al., 2004 ; Thai et al., 2004 ).…”

Synthesis and Structure of a Two-Dimensional Palladium Oxide Network on Reduced Graphene Oxide

“…We therefore attribute the square network to PdO. It is well-known that MR-1 can reduce Pd(II) and produce Pd nanoparticles (PdNPs), 14,18,32,33 the HRTEM structure of which matches Pd(0) (Figure S3). 34 Hence, the nanoparticles are concluded to be PdNPs.…”

“…The dissolved state of Pd(0) atoms or clusters is evidenced by the extracellular presence of PdNPs from Pd(II) reduction by MR-1 in the periplasm at ambient temperature. 32,37 The Pd(0) membrane permeability was accelerated in the hydrothermal process. The presence of Pd(II) in the bulk media 2 h after GO addition is important to ensure continuous Pd(II) reduction to Pd(0).…”

“…It is known that MR-1 reduces Pd­(II) to Pd(0) in the periplasm, where the PdNPs are thus formed. ,, There are two fractions of Pd species before GO is added in the synthesis of S–Pd–GO: one is associated with MR-1 cells, the other one is in the bulk solution. To ascertain their separate roles in the square network formation, the two Pd fractions were separated by centrifugation into supernatant and pellet before GO addition, resulting in S–Pd_CS–GO and S–Pd_CP–GO, respectively (Scheme S1b, “CS” and “CP” for centrifugation supernatant and centrifugation pellet, respectively).…”

“…Proper experimental conditions, for example, a mild temperature, are thus essential to prevent further evolution of the dissolved Pd(0) atoms to PdNPs before the hydrothermal process. The dissolved state of Pd(0) atoms or clusters is evidenced by the extracellular presence of PdNPs from Pd­(II) reduction by MR-1 in the periplasm at ambient temperature. , The Pd(0) membrane permeability was accelerated in the hydrothermal process. The presence of Pd­(II) in the bulk media 2 h after GO addition is important to ensure continuous Pd­(II) reduction to Pd(0).…”