A Light-Triggered Switch Based on Spiropyran/Layered Double Hydroxide Ultrathin Films

Intelligent photoresponsive materials have shown broad applications in antiflake, coating, biomarker, information storage, and optical devices. This article describes the design and fabrication of a photoresponsive switch via a two-step procedure: (i) spiropyran (SP) as a chromophore was encapsulated within a block copolymer (poly­(<i>tert</i>-butyl acrylate-<i>co</i>-ethyl acrylate-<i>co</i>-methacrylic acid), PTBEM) to produce SP@PTBEM micelle; (ii) an organic–inorganic ultrathin film (UTF) was prepared by layer-by-layer (LBL) self-assembly of the negatively charged SP@PTBEM micelle and positively charged MgAl-layered double hydroxide (LDH) nanoplatelets (denoted as (SP@PTBEM/LDHs)_<i>n</i> UTF; <i>n</i> represents the bilayer number). Fluorescence spectroscopy and scanning electron microscopy (SEM) indicate a uniform and ordered layered structure with stepwise growth. The resulting (SP@PTBEM/LDHs)_<i>n</i> UTF serves as an intelligent photoresponsive switch based on the structural transformation between SP and merocyanine (MC), which is triggered by alternate irradiation of UV/visible light. In addition, the UTF exhibits a high reversibility and photostability, which can be potentially used in photochromic materials and devices