Room-temperature ionic liquids (RTILs) are liquids at room temperature and represent a new class of nonaqueous but polar solvents with high ionic conductivity. The conductivity property of carbon nanotubes/RTILs and carbon microbeads/RTILs composite materials has been studied using ac impedance technology. Enzyme coated by RTILs-modified gold and glassy carbon electrodes allow efficient electron transfer between the electrode and the protein and also catalyze the reduction of O2 and H2O2.

No abstract

Supplementary Fig. 1. Summary of previously reported elemental transformation into lower valence species via microbial reduction reactions 1-7. Products of elemental metals (valence = 0), elemental non-metals (valence = 0), metallic oxides/ions (valence ≠ 0) and metalloid (valence = 0) indicated by red, yellow, green and brown respectively, and the methylation of Hg, As, Se, Sn and Te etc are not considered in this diagram. The elements (i.e. O, S, Se and Te), which are in the same group, can be reduced to the products of valence = 0. However, no bio-produced Fe, Ni or Cu (valence = 0) particles, which elements are in the same group with the noble metals, were reported. Through microbial evolution of billions of years, there is potentially a wide diversity of electron transport pathways/mechanisms that are yet to be fully elucidated and understood e.g. what features make the microbial nano-pili electronically conductive? 1 Are there any effects of the membrane bounded metallic-nanoparticles of high electronic conductivity on microbial growth or metabolism? S3 Supplementary Scheme 1 hydrogenase and metal nanoparticles as catalysts for hydrogen oxidation and production. 1) [NiFe]-hydrogenase; 2) the structure of active site; 3) membrane bound bio-nanoparticles. The following mechanism of the nanoparticle production is proposed: Pd(II) is absorbed into the cell and then reduced by hydrogenases and/or cytochrome to elemental Pd(0); periplasmic [FeFe]-hydrogenases serve as the nucleation sites for the initial formation of the metallic nanoparticles, which are then secreted through the cell membrane and undergo size growth. The bio-nanoparticles (e.g. Pd, Pt, Rh and Au) have outstanding catalytic properties in various redox reactions. Fe or Ni (valence = 0) particles generally have little catalytic activity, but the [Fe-Ni] unit (i.e. active site) are key part of hydrogenase, which has been known as catalyst for hydrogen reactions of energy chain in membrane.