Anisotropic behavior of layer-by-layer films using highly disordered copper hexacyanoferrate(II) nanoparticles

[Display omitted] •Stable copper hexacyanoferrate nanoparticles were synthesized with no need of stabilizing agent.•The high number of structural defects generates a strong internal dipole moment in the nanoparticle.•The electroactivity of the PB analogue is attributed to the high number of internal vacancies.•The nanoparticle dipole provoked an anisotropic growth on the LbL modified electrodes. Copper hexacyanoferrate(II) (Cuhcf(II)) nanoparticles (NPs) were synthesized by using a simple and straightforward methodology using aqueous solution without the need of any further passivating agent. The 15nm NPs (obtained by TEM) were fully characterized by XRD, FTIR and Raman spectroscopy that revealed a high number of structural defects. These structural defects are responsible to produce a strong internal dipole moment. This leads to an anisotropic growth onto the electrode surface by using the layer-by-layer technique. Specular Reflectance FTIR corroborates with our assumption. The defects are also responsible for the high electroactivity of the Cuhcf(II)NPs modified electrodes in sodium based electrolytes. Our results contrast with others in which the authors attributed the cell distortion as the main phenomenon.