Molecular simulation studies for intercalation of photoactive dyes into layered double hydroxide

Abstract

Molecular simulation studies were performed to explore the properties of functionalized Mg–Al layered double hydroxides (LDHs). Using molecular dynamics (MD) simulations, the intercalation of photoactive dyes (methyl orange, MO) into a Mg:Al 2:1 LDH system were studied, for which some limited experimental data have been reported (J. Colloid Interface Sci. 2008, 318, 337). The interlayer structure, hydrogen bonding, and consequent swelling of LDH compounds containing MO molecules were shown on the molecular level. Quantum mechanical density functional theory was also employed in order to get the geometry optimization and atomic charges. The concentration profiles, mean square displacement (MSD), and self-diffusion coefficient were calculated using the trajectory files on the basis of MD simulations, and the results indicated that the MO molecules were much more stable when intercalated into the LDH layers. The orientation of the intercalated MO molecules was measured at the interface of the LDH layers. The tail vectors of the MO molecule were tilted with an average angle from 70° to 76°, and most of the angular distribution is about 74.15°, which had a good agreement with the experimental data 74.1°.