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In this study, a dysprosium-based metal–organic framework (MOF) sensor (Dy-MOF) was developed for the ratiometric detection of I− in aqueous medium. Upon excitation at 230 nm, Dy-MOF shows two dominant emission bands at 464 nm and 574 nm assigned to (4F, 4D)5/2 → 6H9/2 + 6F11/2 and 4F9/2 → 6H13/2 transition of Dy3+, respectively, which have different sensitivities toward iodide ions. The introduction of I− slightly weakened the blue emission at 464 nm and significantly quenched the yellow emission at 574 nm. Thus, ratiometric sensing for iodide was realized using the yellow-to-blue intensity ratio of Dy3+. Dy-MOF exhibits superior sensing behavior towards I− with high selectivity, sensitivity and low detection limit (24 nM). This study also provides a strategy for the construction of a ratiometric sensor with dual-emission bands originating from only one emission center. [ABSTRACT FROM AUTHOR]

Detection of Fe(III) and Cu(II) in water is highly desirable because their abnormal levels can cause serious harm to human health and environmental safety. In this work, a ratiometric luminescence sensing platform based on lanthanide-based silica nanoparticles was constructed for the detection of Fe3+ and Cu2+ ions. The terbium-silica nanoparticles (named SiO2@Tb) with dual-emission signals were successfully prepared by grafting Tb3+ ions onto trimellitic anhydride (TMA) functionalized silica nanospheres. It can serve as a ratiometric fluorescent probe for the detection of Fe3+ and Cu2+ ions in water with the green emission of Tb3+ ions as a response signal and the blue emission of silica nanospheres as the reference signal. Significantly, an easy-to-differentiate color change for visual detection was also realized. SiO2@Tb shows high sensitivity even in very low concentration regions towards the sensing of Fe3+ and Cu2+ with low detection limits of 0.75 μM and 0.91 μM, respectively. Moreover, the mechanism for the luminescence quenching of SiO2@Tb was systematically investigated, and was attributed to the synergetic effect of the absorption competition quenching (ACQ) mechanism and cation exchange. This study demonstrates that SiO2@Tb can be employed as a promising fluorescent probe for the detection of Fe3+ and Cu2+ ions, and the combination of lanthanide ions with silica nanoparticles is an effective strategy to construct a ratiometric fluorescent sensing platform for the determination of analytes in environmental detection. [ABSTRACT FROM AUTHOR]

A luminescence sensor based on an europium(III)-based lanthanide–organic framework, [Eu(BCB)(DMF)]·(DMF)1.5(H2O)2 (1), was synthesized via a solvothermal method using 4,4′,4′′-benzenetricarbonyltribenzoic acid (H3BCB) as a bridging ligand. Single-crystal X-ray diffraction indicates that Eu centers are eight-coordinated with a trigonal dodecahedron and a square antiprismatic configuration, and adjacent Eu atoms are bridged by BCB organic linkers to form a 3D rod-packing structure. Photoluminescence studies show that compound 1 emits bright red luminescence and behaves as a multi-responsive luminescent sensor toward 4-nitrophenol (4-NP) and I− and Fe3+ ions in water with high sensitivity, selectivity and low detection limits. Furthermore, the possible luminescence sensing mechanisms were also investigated by PXRD analysis, UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The recognition mechanism for 4-NP and I− ions can be attributed to the competition absorption and that for Fe3+ ions is considered to be a multi-quenching mechanism dominated by competition absorption. This study demonstrates that the lanthanide-based MOF might be a promising candidate for the detection of 4-NP and I− and Fe3+ ions in aqueous medium. [ABSTRACT FROM AUTHOR]

A potent luminescent sensor for the detection of iodide ions was developed based on a terbium(III)-based lanthanide–organic framework [Tb(cpia)(H2O)2]n·nH2O (1), which was prepared under hydrothermal conditions using the 5-(4-carboxyphenoxy)isophthalic acid (H3cpia) bridging ligand. Compound 1 exhibits superior luminescence quenching behavior towards I− with high sensitivity and selectivity among various anions and shows real-time response. Moreover, the mechanism of the selective luminescence quenching response for I− can be mainly explained by the absorption competition between 1 and I−. According to this quenching mechanism, we find that compound 1 can also detect Br− by adjusting the excitation wavelength. Significantly, this work could serve as a general guidance for the design and synthesis of pollutant sensors. [ABSTRACT FROM AUTHOR]

In this study, a dysprosium-based metal-organic framework (MOF) sensor (Dy-MOF) was developed for the ratiometric detection of I - in aqueous medium. Upon excitation at 230 nm, Dy-MOF shows two dominant emission bands at 464 nm and 574 nm assigned to ( 4 F, 4 D) 5/2 → 6 H 9/2 + 6 F 11/2 and 4 F 9/2 → 6 H 13/2 transition of Dy 3+ , respectively, which have different sensitivities toward iodide ions. The introduction of I - slightly weakened the blue emission at 464 nm and significantly quenched the yellow emission at 574 nm. Thus, ratiometric sensing for iodide was realized using the yellow-to-blue intensity ratio of Dy 3+ . Dy-MOF exhibits superior sensing behavior towards I - with high selectivity, sensitivity and low detection limit (24 nM). This study also provides a strategy for the construction of a ratiometric sensor with dual-emission bands originating from only one emission center.

Detection of Fe(III) and Cu(II) in water is highly desirable because their abnormal levels can cause serious harm to human health and environmental safety. In this work, a ratiometric luminescence sensing platform based on lanthanide-based silica nanoparticles was constructed for the detection of Fe 3+ and Cu 2+ ions. The terbium-silica nanoparticles (named SiO 2 @Tb) with dual-emission signals were successfully prepared by grafting Tb 3+ ions onto trimellitic anhydride (TMA) functionalized silica nanospheres. It can serve as a ratiometric fluorescent probe for the detection of Fe 3+ and Cu 2+ ions in water with the green emission of Tb 3+ ions as a response signal and the blue emission of silica nanospheres as the reference signal. Significantly, an easy-to-differentiate color change for visual detection was also realized. SiO 2 @Tb shows high sensitivity even in very low concentration regions towards the sensing of Fe 3+ and Cu 2+ with low detection limits of 0.75 μM and 0.91 μM, respectively. Moreover, the mechanism for the luminescence quenching of SiO 2 @Tb was systematically investigated, and was attributed to the synergetic effect of the absorption competition quenching (ACQ) mechanism and cation exchange. This study demonstrates that SiO 2 @Tb can be employed as a promising fluorescent probe for the detection of Fe 3+ and Cu 2+ ions, and the combination of lanthanide ions with silica nanoparticles is an effective strategy to construct a ratiometric fluorescent sensing platform for the determination of analytes in environmental detection.

A luminescence sensor based on an europium(III)-based lanthanide-organic framework, [Eu(BCB)(DMF)]·(DMF) 1.5 (H 2 O) 2 (1), was synthesized via a solvothermal method using 4,4',4''-benzenetricarbonyltribenzoic acid (H 3 BCB) as a bridging ligand. Single-crystal X-ray diffraction indicates that Eu centers are eight-coordinated with a trigonal dodecahedron and a square antiprismatic configuration, and adjacent Eu atoms are bridged by BCB organic linkers to form a 3D rod-packing structure. Photoluminescence studies show that compound 1 emits bright red luminescence and behaves as a multi-responsive luminescent sensor toward 4-nitrophenol (4-NP) and I - and Fe 3+ ions in water with high sensitivity, selectivity and low detection limits. Furthermore, the possible luminescence sensing mechanisms were also investigated by PXRD analysis, UV-vis spectroscopy and X-ray photoelectron spectroscopy (XPS). The recognition mechanism for 4-NP and I - ions can be attributed to the competition absorption and that for Fe 3+ ions is considered to be a multi-quenching mechanism dominated by competition absorption. This study demonstrates that the lanthanide-based MOF might be a promising candidate for the detection of 4-NP and I - and Fe 3+ ions in aqueous medium.

A potent luminescent sensor for the detection of iodide ions was developed based on a terbium(iii)-based lanthanide-organic framework [Tb(cpia)(H2O)2]n·nH2O (1), which was prepared under hydrothermal conditions using the 5-(4-carboxyphenoxy)isophthalic acid (H3cpia) bridging ligand. Compound 1 exhibits superior luminescence quenching behavior towards I- with high sensitivity and selectivity among various anions and shows real-time response. Moreover, the mechanism of the selective luminescence quenching response for I- can be mainly explained by the absorption competition between 1 and I-. According to this quenching mechanism, we find that compound 1 can also detect Br- by adjusting the excitation wavelength. Significantly, this work could serve as a general guidance for the design and synthesis of pollutant sensors.