Photoelectrochemical properties of electrostatically self-assembled multilayer films formed by three bipolar hemicyanines and H_4SiW_(12)O_(40)

摘要

The electrostatically self-assembled multilayer films of three bipolar hemicyanines with varied alkyl chain lengths were prepared by alternating adsorption of H_4SiW_(12)O~(40) 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/cm~2 with the monochromatic incident photon-to-electron conversion efficiency of 0.75-0.98% while irradiated with 100mW/cm~2 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.