Adsorption of organic layers over electrodeposited magnetite (Fe3O4) thin films

The formation of monolayers of two organic compounds (oleic acid and dodecanethiol) over magnetite films was studied. Magnetite films ranging from 80 nm to 3.75 μm-thick were electrodeposited on Au on glass substrates under galvanostatic control, with deposition parameters optimized for minimum surface roughness. Films were characterised by SEM and AFM, showing granular deposits with a low rms roughness of 5–40 nm measured over an area of 1 μm2. The growth rate was estimated by measuring cross-sections of the thin films. Pure magnetite with an fcc structure is observed in XRD diffractograms. The adsorption of both oleic acid and dodecanethiol on the magnetite films was tested by immersing them in ethanol solutions containing the organic molecules, for different deposition time, temperature and cleaning procedure. Monolayer formation in both cases was studied by contact angle and voltammetric measurements, as well as XPS.

Research highlights
► Adherent low roughness magnetite films ranging from 80 nm to 3.75 μm-thick were electrodeposited on Au/glass substrates under galvanostatic control.
► X-ray diffraction and magnetic measurements corroborates the purity of the electrodeposited magnetite.
► Both dodecanethiol and oleic acid are shown to adsorb on the magnetite prepared at low temperature, significantly inducing the hydrophobicity of the surface.
► Contact angle and voltammetric measurements, as well as XPS confirm the monolayers formation.