A carboxyethyl substituted azacrown ether (CSAE) derivative was intercalated as a second host into a parent host of layered gadolinium hydroxides (LGdH) by an anion-exchange reaction. The influence of intercalation temperature and starting material ratios of CSAE/LRH on the structures and compositions of CSAE-LRH nanocomposites were investigated. Higher temperature and larger initial CSAE-LGdH weight ratios favor of higher degree of ion exchange at a certain range, while lower temperature gives good morphology for the composites. The adsorptive properties for transition and heavy metal ions were studied using the 20 °C-reacted composite, which showed higher adsorptivity toward transition and heavy metal ions, accompanied by the introduction of nitrate anions. The adsorptive capacity for transition metal ions was in the sequence of Cu 2+ > Zn 2+ ∼Ni 2+ ∼Co 2+ with a high selectivity to Cu 2+ . For the heavy metal ions Ag + , Hg 2+ , Pb 2+ , and Cd 2+ , the composite showed markedly high selectivity for Ag + and Hg 2+ . When putting Cu 2+ , Ag + , Hg 2+ , Pb 2+ , and Cd 2+ together, Ag + and Hg 2+ still have higher adsorptive selectivity over Pb 2+ and Cd 2+ , and Cu 2+ has also relatively high selectivity but not as high as Ag + and Hg 2+ . The nanocomposites with a second host in the interlayer are one promising kind of material because of the synergy of the steric effect of the parent host (LRH layer) and the particular characteristics of the secondary host (interlayer crown ether anions).

Partition coefficients for phenol; o-, m-, and p-cresols; 3,5-xylenol; and R-naphthol in an ionic liquid/water twophase system were measured at 298.2 K. 1-Butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) was used as the ionic liquid. Further, the infinite dilution partition coefficients were also determined by extrapolation. The infinite dilution partition coefficients were correlated by regular solution theory. Interaction parameters between phenolic compounds and [bmim][PF 6 ] pairs were determined by plotting the infinite dilution partition coefficients against the solubility parameters of the phenolic compounds. The correlated results are in good agreement with the experimental data.

We demonstrate the first example of exfoliated layered europium hydroxide (LEuH) composites with a fluorescent molecule that exhibit blue luminescence. Co-quenching in the solid state, blue emission (440 nm) in formamide, and green emission (514 nm) in water-formamide were found, for which delamination and swollen states account for the versatile luminescence behaviors.

LRH (R = Tb, Y) composites with ortho-coumaric acid and OS show color-tuning luminescence especially blue luminescence via energy transfer.

Tunable luminescence (quenching or blue shift) of HNA/OS-LRH composites (HNA is 3-hydroxy-2-naphthoic acid; OS is the anionic surfactant of 1-octanesulfonic acid sodium; LRHs are layered rare-earth hydroxides, R = Tb3+, Y3+) in the solid state and delaminated state is reported, which is utilized as an effective fluorescent probe for detecting metal ions. HNA/OS species are intercalated into LRH layers to generate composites of HNA x OS1–x -LTbH (x = 0.10, 0.15, 0.20 , 0.25) and HNA y OS1–y -LYH (y = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30). In the solid state, LYH composites exhibit green emissions (from 493 to 504 nm) with a large blue shift in comparison to the 542 nm emission of free HNA– anions, while in the delaminated state in formamide (FM), the composites display blue emission (480 nm) relative to the green emission (512 nm) of an HNA soltuion in FM. However, LTbH composites display coquenched luminescence in both the solid state and delaminated state. Also, HNA0.25OS0.75-1:1-LYH, HNA0.25OS0.75-1:2-LYH, and HNA0.05OS0.95-1:1-LYH (1:1 and 1:2 are HNA:NaOH molar ratios) show significantly elongated fluorescence lifetimes of 15.35, 14.37, and 12.72 ns, respectively, in comparison with free HNA-Na (6.44 ns), and their quantum yields of 23.40%, 21.97%, and 22.31%, respectively, are much larger than that of free HNA-Na (4.86%). The LTbH composite (HNA0.25OS0.75-1:1-LTbH) has also a relatively higher quantum yield of 12.46%. The HNA0.25OS0.75-1:1-LYH colloid exhibits excellent recognition selectivity for Al3+ over other metal ions (Mg2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, and Hg2+) with distinct fluorescence sensitization. It shows an intense change in its fluorescence emission when it is bound to Al3+ ions, giving a lower detection limit of 6.32 × 10–6 M. This is novel research on the fluorescence chemosensing of LRH composites.

We herein demonstrate the intercalation of several organic benzenepolycarboxylic compounds, terephthalic acid (TC), 1,3,5-benzenetricarboxylic acid (BTC) and 1,2,4,5-benzenetetracarboxylic acid (BTCC), into the layered terbium hydroxide (LTbH) and the sensitized luminescence of these organic species for the layer Tb 3+. All of the as-prepared products demonstrated characteristic XRD diffractions attributed to layered materials. Compared with the NO 3-LTbH precursor, efficient energy transfer from intercalated organic anions to Tb 3+ centers in LTbH layers took place, thus markedly enhancing the Tb 3+ luminescence. The relationship between the triplet energy levels of the organic guests and the energy level of Tb 3+ was analyzed to explain the sensitization effect and energy transfer from the gallery sensitizers to the layer Tb 3+ ions. The fluorescence lifetimes of NO 3-LTbH, TC-LTbH, BTC-LTbH and BTCC-LTbH were determined to be 0.131, 0.315, 0.579 and 0.642 ms, respectively, indicating significantly increased lifetimes of the LTbH composites intercalated with the organic species.

We demonstrate a novel example of tunable luminescence and the application of the delaminated FLN/OS-LRH composites (LRHs are layered rare-earth hydroxides, R = Tb, Y; FLN is the fluorescein named 2-(6-hydroxy-3-oxo-(3H)-xanthen-9-yl)benzoic acid; OS is the anionic surfactant 1-octane sulfonic acid sodium) in detecting Fe(iii) ions. The FLNxOS1-x species (x = 0.02, 0.05, 0.10, and 0.20) are intercalated into the LTbyY1-yH layers (y = 1, 0.9, 0.7, 0.5, 0.3, 0.1 and 0) by ion exchange reactions to yield the composites FLNxOS1-x-LTbyY1-yH. In the solid state, the LYH composites display green emission (564 nm) arising from the organic FLN, while in LTbH composites, the luminescence of the Tb3+ in the layers (545 nm) and the FLN in the interlayers is co-quenched. In the delaminated state in formamide (FM), FLNxOS1-x-LTbH composites display green to yellowish-green luminescence (540-574 nm) following the increasing FLN/OS ratio; while the FLN0.02OS0.98-LTbyY1-yH composites show green emission at ∼540 nm. The fluorescence lifetimes of the composites (4.22-4.63 ns) are comparable to the free FLN-Na, and the quantum yields (31.62-78.70%) of the composites especially that (78.70%) of the FLN0.02OS0.98-LYH are much higher than that (28.40%) of free FLN-Na. The recognition ability of the FLN0.02OS0.98-LYH composite for metal cations is researched. The delaminated FLN0.02OS0.98-LYH colloidal suspension exhibits high selectivity for Fe3+ over other ions (Mg2+, Al3+, Ni2+, Co2+, Cu2+, Zn2+, Mn2+, Pb2+, and Cd2+) with fluorescence quenching, which can work as a kind of turn-off fluorescence sensor for the detection of Fe3+. The detection limit of Fe3+ is determined to be 2.58 × 10-8 M and the quenching constant (Ksv) is 1.70 × 103 M-1. This is the first work on LRH materials working as a chemosensor for recognising metal cations. It provides a new approach for the design of LRH materials to be applied in fluorescence chemosensing.

The organic compound of coumarin-3-carboxylic acid (CCA), deprotonated beforehand by NaOH, and the 1-octane sulfonic acid anion (OS) were co-intercalated into the gallery of the layered europium hydroxide (LEuH) via an ion exchange method. Different molar ratios of CCA/OS and NaOH/CCA gave rise to the composites of CCAOS-LEuH (x = 0.8-1.0) showing different emission intensities. In formamide (FM), all composites were delaminated and the formed colloidal suspensions exhibited enhanced red luminescence of Eu in comparison with the OS-LEuH without CCA. Also, the red emissions of the composites were different from the violet emission (421 nm) of free CCA and blue emission (471 nm) of CCA anions in different deprotonation states. The energy levels of CCA and Eu were analyzed to explain the sensitization effect for Eu luminescence. The fluorescence lifetimes of CCAOS-LEuH-1 : 1, CCAOS-LEuH-1 : 1, CCAOS-LEuH-1 : 2, and CCAOS-LEuH-1 : 2 were determined to be 0.705, 0.704, 0.699 and 0.638 ms, respectively, indicating significantly longer lifetimes. The PL quantum yields of ∼10% demonstrate the excellent luminescence properties of the as-prepared CCAOS-LEuH composites. This is the first report on the sensitized luminescence properties of layer Eu ions in LRH composites in the delaminated state. The intriguing red luminescence of delaminated LEuH composites offers a promising approach to achieve efficient luminescent film materials.