Bis(8-hydroxyquinolate-5-sulfonate)zinc intercalated layered double hydroxide and its controllable luminescent properties

Abstract

Bis(8-hydroxyquinolate-5-sulfonate)zinc anion (ZQS²⁻) and dodecyl sulfonate anion (DDS⁻) have been co-intercalated into the layered double hydroxide host (M_nAl LDH, M²⁺ = Mg, Zn, n = 2, 3) by a hydrothermal co-precipitation method, with samples denoted as DDS–ZQS(x%)/LDH (x stands for the molar percentage content of ZQS with respect to DDS + ZQS). The structure and chemical composition of the resulting compounds were characterized by X-ray diffraction (XRD), FT-IR and elemental analysis. Their films obtained by the solvent evaporation method have a well-defined c-orientation confirmed by XRD and scanning electron microscopy (SEM). Thermogravimetry and differential thermal analysis (TG–DTA) results elucidate that the thermal stability of ZQS is enhanced upon co-intercalation. The fluorescent studies show that the luminous behavior (wavelength, intensity, lifetime and quantum yield) of ZQS is correlated with the fluorophore content and can be modulated by controlling the host–guest and guest–guest interaction through changing the ratio of DDS to ZQS, metal species and positive charge density of the LDH host layer. DDS–ZQS(5%)/Mg₂Al LDH exhibits the optimal luminous intensity and the longest lifetime among the DDS–ZQS(x%)/Mg₂Al LDH samples.