Energy conversion in nature is generally achieved by nano-scale mechanistic coupling of thermodynamic downhill with uphill processes. The most prominent example is the proton concentration gradient across the inner mitochondrial membrane, which provides the energy for the formation of ATP. The coupling of downhill proton transfer across the membrane with uphill ADP phosphorylation to ATP is achieved by the ATP synthase complex.<br/>Here we introduce a chemically very simple but conceptually similar approach, in which the downhill precipitation of barium sulphate is mechanistically coupled to an electron transfer reaction. The principle is illustrated in the figure. Our system consists of a water-in-oil emulsion that contains droplets of two different compositions. Importantly, barium and sulphate ions are initially in different droplets and cannot precipitate. The mechanism that brings them together is a transporter gold nanoparticle with a crown ether ligand shell (CE GNPs) that can complex barium ions. The particles partition between the water and oil phase and enable the transport of barium ions from one type of droplet to the other followed by the precipitation of barium sulphate. To maintain charge neutrality, it is not possible that barium ions alone are transferred. Therefore, we have added a redox couple (here Ru(II)/Ru(III)) to enable simultaneous electron transfer via the gold particle. Results are presented that show that precipitates of barium sulphate are only formed in the presence of the gold transporter particles and that the amount of the redox couple present also controls the amount of precipitate formed. The possibility of real energy conversion by driving uphill redox reactions with coupled downhill precipitations is discussed.

Bio-inspired energy conversion in non-equilibrium nano-systems: Electron-transfer coupled precipitation

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.