Electrospray ionisation is a non-thermal route to get large, fragile and non-volatile molecules into the gas-phase, either for deposition directly onto a surface or for extraction into vacuum for further manipulation before being measured or deposited. Passing a solution of molecules (or even a suspension of nanoparticles) through a high-voltage capillary, the electric field draws the ions downstream into a Taylor cone, and at the tip of the cone the surface tension can no longer hold and a jet is emitted. Instabilities cause the jet to break up into charged droplets which undergo a cascade of fission events caused by solvent evaporation and Coulomb explosion.
The charged ions are extracted into vacuum through a grounded entrance capillary which is often heated to aid desolation, before passing through differentially-pumped molecular beam skimmers and apertures to reduce the pressure to the desired range for deposition. This non-filtered approach provides the widest possible range of molecules and nanoparticle that can be deposited on surfaces in vacuum. Even molecules that resist ionisation, such as many polymers can be deposited with our sources as the neutral species can be carried by the ionised solvent into the gas-phase.
Combining our UHV-compatible electrospray deposition sources with surface science techniques such as XPS, STM, RPES and XAS have successfully led to unprecedented insights into complex molecules including giant porphyrin nano rings, single molecule magnets, organometallic dyes, polymers and proteins.