Luminescent ultrathin film of anionic styrylbiphenyl derivative-layered double hydroxide and its reversible sensing for heavy metal ions

Ordered ultrathin films (UTFs) with blue luminescence based on a styrylbiphenyl derivative (BTBS) and Mg-Al-layered double hydroxide (LDH) nanosheets have been constructed employing the layer-by-layer assembly technique. UV-visible absorption and fluorescence spectroscopy showed a stepwise and regular growth of the films upon increasing the number of deposition cycles. XRD, AFM and SEM indicated that the films possess a periodic layered structure with a period of ca. 1.5 nm, and uniform surface morphology. The film thickness can be precisely controlled in the range ca. 15-53 nm. The BTBS-LDH UTFs exhibit improved UV-light resistance capability compared with the pristine BTBS and show well-defined polarized photoemission, with anisotropy of ca. 0.24. The UTFs show a fast, selective and reversible luminescent response to aqueous solutions containing different heavy metal ions, with the most significant luminescent quenching occurring for the Hg2+ solution, shedding light on the fact that these films can serve as a new type of selective solid luminescent metal-ion sensor.