Preparation and second-harmonic generation properties of a self-assembled multilayer film based on nanoporous isopolyoxomolybdate and bipolar hemicyanine

An electrostatic self-assembled multilayer film has successfully been prepared by alternating adsorption of a wheel-shaped nanoporous isopolyoxomolybdate and a bipolar hemicyanine derivative, as monitored by absorption spectroscopy. The square roots of second-harmonic intensities of the film exhibit quadratic dependence on film thickness up to 10 layers. The average titled angle of the nonlinear optical chromophores to the substrate normal is derived to be 34 by polarized second-harmonic generation measurements.