Luminescent layered europium hydroxide as sensor for multi-response to Cr2O7 2− or MnO4 − based on static quenching and inner filter effect

Highlights: • A novel layered hydroxide of LEuH-Cl was synthesized as luminescent sensing material. • LEuH-Cl revealed selective luminescent quenching responses to MnO₄⁻ and Cr₂O₇²⁻. • Facile detection of MnO₄⁻ and Cr₂O₇²⁻ was achieved by LEuH-Cl with high sensitivity. • LEuH-Cl detected MnO₄⁻ and Cr₂O₇²⁻ by coupled static quenching and inner filter effect. Through a simple hydrothermal reaction, LEuH-Cl (where LEuH and Cl denote layered europium hydroxide and a chlorine ion, respectively) was synthesized. Its structure and properties were similar to those of layered double hydroxides (LDHs). The material was composed of europium hydroxide host layers with a positive charge and a guest interlayer with chlorine ions. The hydrotalcite-like structure gives it excellent anion exchange abilities, and the host shows an intense photoluminescence (PL), mainly through ⁵D₀→⁷F_J (J = 0,1,2,3, and 4). MnO₄⁻ or Cr₂O₇²⁻ can be directly adsorbed by LEuH-Cl in an aqueous solution due to the large number of exchangeable chlorine ions, thereby resulting in a static quenching effect (SQE) and forming an inner filter effect (IFE) system, which leads to the direct quenching of the PL intensity. Based on this characteristic, the concentration of these two substances in an aqueous solution can be detected quickly and simply. Based on the experimental results, LEuH-Cl exhibited high selectivity and sensitivity toward MnO₄⁻ and Cr₂O₇²⁻ in an aqueous solution. The detection limits of MnO₄⁻ and Cr₂O₇²⁻ were calculated to be 3.43 and 1.19 μM, respectively. This proved the feasibility of using the material for the direct detection of multiple substances. The quenching caused by the anion exchange of layered rare-earth hydroxides (LRHs) was further explored.