Photoelectrochemical properties of electrostatically self-assembled multilayer films formed by three bipolar hemicyanines and H4SiW12O40

The electrostatically self-assembled multilayer films of three bipolar hemicyanines with varied alkyl chain lengths were prepared by alternating adsorption of H4SiW12O40 and these hemicyanines, and characterized by UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy and cyclic voltammetry. The results showed that these inorganic–organic composite films were uniformly deposited with good electrochemical activity. Photoelectrochemical investigations showed that the films exhibited large cathodic photocurrent densities of 0.36–1.02 μA/cm2 with the monochromatic incident photon-to-electron conversion efficiency of 0.75–0.98% while irradiated with 100 mW/cm2 polychromatic light (730 nm > λ > 325 nm) at an applied potential of −0.2 V vs. saturated calomel electrode, being strongly dependent on the alkyl chain lengths.