An apparatus for producing ions can include an emitter having a first end and a second end. The emitter can be coated with an ionic liquid room-temperature molten salt. The apparatus can also include a power supply and a first electrode disposed downstream relative to the first end of the emitter and electrically connected to a first lead of the power supply. The apparatus can also include a second electrode disposed downstream relative to the second end of the emitter and electrically connected to a second lead of the power supply.