Reactivity in Aqueous Droplets
Chemical reactions have been demonstrated to proceed faster when confined to very small volumes. Using stochastic nanoelectrochemistry, we study reactivity in nanodroplets (radii ~100-1000 nm) that are suspended in an immiscible liquid phase. When a droplet collides with a microelectrode (radius ~5 micrometers), we track the reaction rate (current), and can rigorously account for the size of each nanodroplet. With this technique we operate with the ultimate analytical sensitivity, measuring one nanodroplet-at-a-time.
Chemistry in confined volumes, such as aqueous droplets, is different from bulk, continuous water. However, few techniques are available to probe interfacial reactivity in complex, multiphase environments. One multiphase environment we can probe through electrochemistry is the oil|water|conductor (three-phase) interface. Electrodeposition of cobalt and nickel at this multiphase interface results in ringlike structures that can be characterized with tens of nanometers precision in scanning electron microscopy and energy dispersive X-ray spectroscopy.