A composite material of europium hydroxide (Eu(OH) 3 ) and glycine (Gly) is synthesized successfully to produce single phase material (Eu(OH) 3 -Gly) which exhibits extremely selective capturing and high removal rate towards uranyl (UO 2 2+ ) ion in an aqueous solution. Eu(OH) 3 -Gly displayed distribution coefficient (K d ) of 3.23 × 10 7 mL/g and removal rate of 100% to lower UO 2 2+ ion concentration from 25 ppm to <1 ppb inside 15 min and these criteria place Eu(OH) 3 -Gly among the top existing adsorbents for such adsorption. Adsorption kinetics for UO 2 2+ follows pseudo-second-order model, proposing a chemisorption adsorption mechanism mainly via H 2 N-U-NH 2 and O-U-O interactions. Eu(OH) 3 -Gly showed good stability after the removal of uranyl ion as investigated by FT-IR and thermogravimetric analysis (TGA) methods. According to TG analysis, Eu(OH) 3 -Gly showed less weight loss (23.7%) after adsorption compared with that of before adsorption (32%), suggesting that the attachment of uranium to the adsorbent contributed for the improvement of the thermal stability of Eu(OH) 3 -Gly.
Lu Liu,Jingjie Yu,Shikao Shi,Jiye Wang,Huihua Song,Ruikang Zhang,Lianshe Fu
The design and fabrication of rare earth ions incorporated into the inorganic/organic hybrid materials have attracted growing attention for seeking improved optical properties and photofunctional performances. In this paper, a novel hybrid composite based on the layered rare earth hydroxides was successfully prepared by the ion-exchange and intercalation chemical process. The rare earth elements in the composite contain gadolinium (Gd) and europium (Eu) and the molar ratio of Gd to Eu is kept constant at 1.9 : 0.1. Organic sodium dodecyl sulfonate and dye coumarin-3-carboxyllc acid are simultaneously incorporated into the layered rare earth hydroxides as supporting agent and light-harvesting antenna, respectively. The resulting hybrid layered rare earth hydroxides exhibit the enlarged interlayer distance with about 2.60 nm, and the chemical composition was confirmed through X-ray diffraction, carbon, hydrogen and nitrogen (CHN) elemental analysis , infrared spectroscopy, and thermogravimetric analysis . The layered solid compound shows the characteristic red emission corresponding to the 5 D 0 → 7 F 2 transition of Eu 3+ ion, and the luminescence intensity of the optimized compound is greatly enhanced as compared to its corresponding nitrate and the hybrid composite without the introduction of dye molecule. The hybrid layered rare earth hydroxides can be exfoliated into bright colloidal solution, which show superior recognition capability to Cu 2+ ion with the distinct luminescence quenching . The large quenching constant (1.4 × 10 4 L/mol) and low detection limit (0.35 μmol/L) are achieved for Cu 2+ ion, implying a “turn-off” fluorescent sensor for Cu 2+ detection. Moreover, a transparent film was prepared based on the colloidal solution and displays the typical red emission in folded shape. The new hybrid compound with enhanced luminescence and excellent photofunctional performances is expected to be applied in the fields of fluorescent sensing and flexible optical devices.
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 5 D 0 → 7 F J (J = 0,1,2,3, and 4). MnO 4 − or Cr 2 O 7 2− 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 MnO 4 − and Cr 2 O 7 2− in an aqueous solution. The detection limits of MnO 4 − and Cr 2 O 7 2− 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.
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