Polarized vibrational spectra of Prussian Blue films: Spectroscopic evidence of columnar growth

We describe the preparation of Prussian Blue films with several thicknesses, and their characterization by means of cyclic voltammetry and polarized reflection FTIR spectroscopy. The electrochemical experiments demonstrated a direct relationship between the film thickness and its intrinsic conductivity. The vibrational spectra showed asymmetrical bands in the vicinity of the cyanide stretching band. The s-polarization bands showed a shift to higher frequencies, while the p-polarization bands showed a downshift with increasing film thickness. The presence of shifted cyanide stretching bands in the s- and p-polarizations is attributed to the columnar shape of Prussian Blue grains formed in the growth process.