Controllable Nanocage Structure Derived from Cyclodextrin-Intercalated Layered Double Hydroxides and Its Inclusion Properties for Dodecylbenzene

Abstract

A novel nanocage structure derived from carboxymethyl-� -cyclodextrins (CMCDs) intercalated in layered double hydroxides (LDHs), whose gates can be controlled by the process of swelling/drying the CMCD-LDH, has been prepared. Furthermore, the extent of opening of this nanocage structure can be controlled by swelling in different solvents. Dodecylbenzene (DDB) as the guest molecule has been incorporated into the nanocage structure through two different routes: intercalation of CMCD in the LDH followed by inclusion of DDB (intercalation-inclusion method) and inclusion of DDB in CMCD followed by intercalation of the host-guest complex into the LDH (inclusion-intercalation method). For the convenience of using this nanocage as an absorbent and storage vessel for neutral guest, films of the resulting composite materials (CMCD-LDH) were fabricated by the method of solvent evaporation on glass substrates. The structures, chemical compositions, morphologies, and physicochemical properties of the materials were fully studied. Moreover, the effects of the combined confinement of both the LDH layers and the cyclodextrin cavity on the encaged guest were investigated. Compared with the confinement effect produced by cyclodextrin only, this double-confinement imposes stronger restrictions on the mobility of the guest molecule, which leads to a blue shift of the fluorescence spectrum and increases the decay time of the guest. Therefore, this structured nanocage might have potential applications as adsorbents, synergistic agents, and storage vessels for neutral molecules.