Photochromic Langmuir–Blodgett films based on polyoxomolybdate and gemini amphiphiles

Abstract

Novel photochromic hybrid organized molecular films composed of polyoxomolybdate (PMo₁₂) and a series of gemini amphiphile (BisBC18Nn, n = 1, 2, 3) with different hydrophilic spacer length were fabricated by the Langmuir–Blodgett (LB) technique. When these gemini amphiphiles were spread on an aqueous PMo₁₂ subphase, hybrid monolayers were formed in situ at the air/water interface through electrostatic interaction. These hybrid monolayers were subsequently transferred onto solid substrates and characterized by UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), atomic force microscopy (AFM) and cyclic voltammetry (CV). The hybrid multilayer films showed photochromic property, i.e., the color of BisBC18Nn/PMo₁₂ hybrid films changed from pale yellow to cyan under UV irradiation and decoloration occurred when the films were heated in the air. Such processes could be repeated many times and the films exhibited excellent photochromic reversibility. A slight difference in the coloration of the hybrid films with different spacer lengths was observed.