Abstract
SummaryDesulfovibrio desulfuricans reduces Pd(II) to Pd(0)‐nanoparticles (Pd‐NPs) which are catalytically active in 2‐pentyne hydrogenation. To make Pd‐NPs, resting cells are challenged with Pd(II) ions (uptake), followed by addition of electron donor to promote bioreduction of cell‐bound Pd(II) to Pd(0) (bio‐Pd). Application of radiofrequency (RF) radiation to prepared 5 wt% bio‐Pd catalyst (60 W power, 60 min) increased the hydrogenation rate by 70% with no adverse impact on selectivity to cis‐2‐pentene. Such treatment of a 5 wt% Pd/carbon commercial catalyst did not affect the conversion rate but reduced the selectivity. Lower‐dose RF radiation (2–8 W power, 20 min) was applied to the bacteria at various stages before and during synthesis of the bio‐scaffolded Pd‐NPs. The reaction rate (μ mol 2‐pentyne converted s‐1) was increased by ~threefold by treatment during bacterial catalyst synthesis. Application of RF radiation (2 or 4 W power) to resting cells prior to Pd(II) exposure affected the catalyst made subsequently, increasing the reaction rate by 50% as compared to untreated cells, while nearly doubling selectivity for cis 2‐pentene. The results are discussed with respect to published and related work which shows altered dispersion of the Pd‐NPs made following or during RF exposure.
Highlights
The goal of this study is to establish the scope for using electromagnetic intervention as a tool to produce bio-NPs with enhanced catalytic properties, as a first step towards ‘steering’ bio-NPs targeted towards specific reaction outcomes, in this case selectivity to the cis-ene product of 2-pentyne hydrogenation
At a power of 8W, a temperature increase of between 2 and 6°C was observed in the sample after 20 min. These experiments were restricted to 8W or less for a maximum of 20 min in order to avoid thermal damage or stress to the bacteria
This study reveals different outcomes of RF treatment of dried bound Pd(II) to Pd(0) (bio-Pd) catalyst and of living cells (with or without Pd(II)) with a lower RF dose and we suggest, two mechanisms of catalyst activity enhancement
Summary
Bacteria can reduce precious metals, forming metallic nanoparticles (NPs) in cell surface layers (Mikheenko et al, 2008; Deplanche et al, 2010, 2014) and intracellularly (Omajali et al, 2015; Gomez-Bolivar et al, 2019), while killed cells make negligible Pd-NPs (Mikheenko et al, 2008; Deplanche et al, 2010). An important factor for sustainability, some bio-NPs are promising heterogeneous catalysts for remediation and ‘green chemistry’ (Deplanche et al, 2011; De Corte et al, 2012; Hennebel et al, 2012; Singh, 2015). Conditions which are known to change the structure or function of the cell membrane(s) and/or associated enzymes may impact upon the size, distribution, shape or hydrophobicity of the metallic NPs. A role for bacterial hydrogenases in bio-Pd-NP synthesis was shown using mutants deficient in one or more hydrogenase enzymes; such alterations, affecting the patterning of Pd-NPs (Mikheenko et al, 2008; Deplanche et al, 2010), could enhance the catalytic activity as shown in Cr(VI) reduction (Rousset et al, 2006)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
