Fabrication, spectroscopic and photofunctional studies of layered lutetium-dysprosium hydroxides

The spectroscopic studies of layered rare-earth hydroxides (LRHs) have aroused great interests owing to the unique features of combing rare-earth ions with diverse anions. In this work, some anions were incorporated into layered lutetium-dysprosium hydroxides (LLuH:Dy) by the hydrothermal and ion exchange process, in which Dy³⁺ ion acted as the emission center. The results manifest that the assemblies possess clearly lamellar structure and flake shape, and emit the characteristic yellow and blue light of Dy³⁺ under ultraviolet excitation. The inorganic WO₄^2- intercalated LLuH:Dy shows enhanced luminescence under the excitation with 280 nm which originates from the O-W charge transfer band. The more fantastic is that the assembly produces bright cyan light due to the appropriate yellow/blue light intensity ratio, and can transform into transparent and flexible film by mixing with certain polymer. Moreover, the intercalation of organic chromophore benzenetetracarboxylic anion into LLuH:Dy also greatly promotes the Dy³⁺ luminescence, and can easily form the nanosheet colloid through combining with surfactant dodecyl sulfonate. The colloid is very stable at ambient temperature and displays excellent selectivity, sensitivity and accuracy for detecting metal Co²⁺ in aqueous media, constructing a superior fluorescence sensor for Co²⁺ with a detection limit of 2.65 × 10^-7 mol/L. This work expands the photofunctional performances of LRHs in the form of transparent film and colloidal state.