Peter Nemes, Samita Goyal, and Akos Vertes. Department of Chemistry, George Washington University, 725 21-st Street, N. W., Washington, DC 20052
Liquid ejection through an electrified capillary exhibits a wide variety of axial modes. Depending on the emitter voltage, flow rate and liquid properties, dripping, burst, pulsating, astable and cone-jet modes can be established. Due to the electrohydrodynamic and electrochemical processes at the liquid emitter interface, in the different spraying modes the ejected liquid shows variations in its composition. A simple example of reactive electrosprays is driven by the solute oxidation processes initiated at metallic emitters due to the spray current. We demonstrate that this process is less prominent in the cone-jet mode than in pulsating mode. Spraying protein solutions in different regimes can result in shifting the unfolding-refolding dynamics. For example, cone-jet mode favors unfolding, whereas the pulsating regime promotes refolding. Unfolding is driven by the pH change induced by enhanced water oxidation in the cone-jet mode. Reactive electrosprays have potential preparative (e.g., redox chemistry for nanomaterials, biocomposites and electrospinning) and analytical (e.g., ion production, protein conformation and complexation changes) applications.