Yao Bao

Photoluminescence of Tb-doped MgAl-LDHs depending on phase transition caused by annealing

Abstract This paper presented the photoluminescence of Tb-doped Mg-Al layered double hydroxides (Tb-doped MgAl-LDHs) depending on phase transition caused by annealing. Tb-doped MgAl-LDHs structure transformed from hexagonal LDHs, cubic MgO to spinel MgAl 2 O 4 phase as temperature varied from 200 to 1000 °C. Emission and excitation spectra of Tb-doped MgAl-LDHs obviously changed with phase transformation. The emissions of Tb 3+ ions attributed to 5 D 4 → 7 F J transitions ( J =3, 4, 5, 6) were observed in the emission spectra of all the Tb-doped samples. The ratio of ( 5 D 4 → 7 F 5 )/( 5 D 4 → 7 F 6 ) emission intensity, which was sensitive to surroundings of Tb 3+ ion, markedly enhanced with temperature rising to 600 from 400 °C. Over 600 °C, the ratio of ( 5 D 4 → 7 F 5 )/( 5 D 4 → 7 F 6 ) intensity tended to decreasing up to 1000 °C. The change concerning the ratio of the ( 5 D 4 → 7 F 5 )/( 5 D 4 → 7 F 6 ) emission intensity might be due to various surroundings of Tb 3+ induced by phase transformation.

Study on structure and fluorescence of Tb-doped CaAl LDHs prepared in ethanol/water system

An important material applied in biological fluorescent detector and medical treatment is highly desired in view of the biocompatibility and fluorescent property. Here, Tb-doped CaAl-layered double hydroxides with Ca2+/(Al3+ + Tb3+) molar ratio of 1.0, 2.0, 3.0, and 4.0 have been successfully prepared in a mixed solution of ethanol and water in a reasonable proportion. Chemical compositional analyses revealed that the experimental value of Ca2+/(Al3+ + Tb3+) molar ratio present in the samples was close to the initial value of Ca2+/(Al3+ + Tb3+) molar ratio of raw reactants. In the X-ray diffraction results, it was found that the typical layered double hydroxides structure can be kept between the Ca2+/(Al3++Tb3+) molar ratio of 1.0 and 4.0. The structural type of the Tb-doped CaAl-layered double hydroxides was monoclinic form when the Tb content was less than of 3.0 %, while rhombohedral form appeared and retained as the content of Tb3+ is kept between 3.0 and 5.28 wt%. Photoluminescence shows strong green emissions attributed to 5D4-7FJ (J = 3, 4, 5, 6) transition of Tb3+ ions incorporated in the Tb-doped CaAl-layered double hydroxides.Graphical AbstractA series of Tb-doped CaAl-LDHs with different molar ratio of Ca2+/(Al3+ + Tb3+) have been synthesized by co-precipitation in a mixed ethanol/water system. Strong green emission appeared in the Tb-doped CaAl-LDH. The Tb–CaAl-LDHs may be a promising biological fluorescent material because of the biocompatibility of Ca2+ ions as well as the fluorescent property of Tb3+ ions.

Intercalation of cytosine into Eu 3+ -doped hydrocalumite and their fluorescent responses

Intercalation of cytosine into Eu3+-doped hydrocalumites and the fluorescence of the Eu3+-doped hydrocalumite response to cytosine has been investigated. XRD patterns showed that the basal spacing of Eu-doped hydrocalumite obviously increased after it exposed to various content of cytosine, revealing the intercalation of cytosine into Eu3+-doped hydrocalumite. TG-DSC curves and IR spectra of the intercalated samples are different from that of the Eu-doped hydrocalumite and cytosine, indicating the interaction between the Eu3+-doped hydrocalumite and cytosine. Fluorescent spectra suggested that the fluorescent changes of Eu3+-doped hydrocalumite depended on the concentration of cytosine solution. This fluorescent change would be potential application in biological probe in view of the biocompatibility of Ca2+ ions and the fluorescence of Eu3+ ions. Moreover, the Eu3+-doped hydrocalumite would be a healthy and cheap fluorescent material applied in biology or healing drugs fields.