Luminescent layered europium hydroxide as sensor for multi-response to Cr2O72− or MnO4− based on static quenching and inner filter effect

Abstract

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→7FJ (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.