The Electrospray Ionization (ESI) technique, allows to bring large molecules as intact and isolated units in the gas phase. Its ability to generate sprays of monodisperse charged particles can be exploited to deposit thin and uniform coating films of fine particles of different materials. The ESI technique uses a low-concentration solution of the molecule of interest flowing in a small capillary toward a metallic emitter held at high voltage (typically a few kV).
At the tip of the emitter, the competition of the surface tension of the liquid and the high field results in the so-called 'Taylor cone', inside which Coulomb explosion creates a spray of charged droplets with sizes down to nanometers. As the solvent evaporates the size of the droplet deceases and at the end a gas of molecular ions is formed. This approach provides dry depositions at ambient pressure or in controlled atmosphere and can be easily automatized and applied on a large scale. The system is available in the DepEST lab of the Montelibretti Section.
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