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Keywords:

  • polythiophene;
  • layered double hydroxide;
  • polarized red luminescence;
  • pH sensor;
  • periodic density functional theory

Abstract

Luminescent ordered ultrathin films (UTFs) based on a sulfonated polythiophene (SPT) and Mg–Al-layered double hydroxide (LDH) nanosheets have been fabricated by the layer-by-layer assembly method. UV-visible absorption and fluorescence spectroscopy showed that there was a stepwise and regular growth of the films with increasing number of deposition cycles. XRD, AFM, and SEM showed that the films had a periodic layered structure with a period of ca. 3.0 nm, and that the thickness can be finely controlled within the range ca. 26–100 nm. The SPT/LDH UTFs show well-defined polarized photoemission with an anisotropy of ca. 0.3, and they show a reversible luminescence response to changes in pH. Periodic density functional theoretical calculations gave a band energy of 1.85 eV for the SPT/LDH system and showed that the valence electrons of SPT can be confined in the energy wells formed by the LDH monolayers, which effectively inhibits both the nonradiative relaxation and the π–π stacking interaction of the polymer chromophores. © 2010 American Institute of Chemical Engineers AIChE J, 2011