Thin films of synthetic melanin

We have developed a new synthetic route to melanin, using different organic solvents, namely dimethyl sulfoxide and N,N-dimethyl formamide. Contrary to conventional water based melanin thin films can be made with organic solvents. Thin films were made either by room temperature solvent evaporation (casting) or using spin coating. X-ray diffraction, thermogravimetry, infrared transmission spectroscopy, UV–VIS transmission spectroscopy, electron spin resonance, atomic force microscopy (AFM) and temperature dependent conductivity have been used to characterize the material obtained. The new synthetic material is found to be similar to melanin made in water, however with an increase in thermal stability. AFM results shows that the thin films are made of graphitic-like planar structures, with root mean square roughness of ∼0.3 nm, separated by steps ranging from 1 to 3 nm in height. These sheets have lateral extensions of several microns, which make this new material potentially interesting as a 2D organic polymer.