Uniform trend in layer-by-layer deposition of heteropolytungstates.

The layer-by-layer deposition of films including polyoxometalates (POMs) results in a very interesting range of applications in various fields such as electrochemical devices and as photochromic coatings. However, the fundamental knowledge of the parameters responsible for tuning the properties of the film (i.e. relation between the structure and composition of the POM and the properties of the final film) is still lacking. The current work establishes the relationship between the film thickness, the quantity of POM incorporated in each layer and the electrochemical response of the (PAH-POM)x coatings, where PAH is poly(allylamine hydrochloride). The results presented in this work show that the film thickness, composition and electrochemical activity scale proportionally with the number of W atoms in a series of heteropolytungstates ranging from 5 to 48 (P2W5, PW12, P2V3W15, P2W18, P5W30, P8W48). The obtained results allow us to establish a method to predict the behavior as well as the properties of the film based on the nature of the POM used.