Charge emissions from Electrosprays in vacuum: mixtures of formamide with methylammonium formate

Abstract

The charge/mass distribution f(q/m) of nanodrops and ions electrosprayed in vacuum from mixtures of formamide (FM) and methylammonium formate (MAF) is studied by time of flight mass spectrometry at MAF/FM volumetric concentrations of 5%, 10%, 25% and 50%. Positive and negative polarities yield comparable f(q/m) curves, though the negative mode yields ~30% larger currents. On shifting from the highest to the lowest liquid flow rates, at which a cone-jet is stable, the more conducting solutions evolve from mostly drop to primarily ion emission. A purely ionic regime is not reached under any condition, but the drops achieve unusually high q/m. As a result, these sprays have excellent electrical propulsion characteristics, some being able to cover a 25-fold range of average q/m with a propulsive efficiency typically in the range of 80%. Results of formamide electrolytes with formates and nitrates of several other amines are more briefly reported.