A 3D Zn(II)-based metal-organic framework, [Zn2(TPOM)(NH2–BDC)2]·4H2O (NH2–Zn-MOF, TPOM = tetrakis(4-pyridyloxymethylene)methane and NH2–BDC = 2-aminoterephthalic acid), was successfully achieved via a hydrothermal reaction. The framework adopts a (4,2)-connected 3D network, with the Schlafli symbol {62·84}. This complex exhibits strong luminescence emission, which is selectively sensitive to Cr(III) and Cr(VI) ions. More importantly, the fluorescence explorations indicated that it represents the first example of MOF-based fluorescent probes for detecting Cr(III) through a fluorescence enhancement mechanism. In addition, it also shows highly selective and sensitive detection of electron-deficient nitroaromatic compounds through fluorescence quenching. These properties make the NH2–Zn-MOF a potential luminescence sensor for selectively detecting these chemicals.

An amino-decorated dual-functional metal–organic framework for highly selective sensing of Cr(III) and Cr(VI) ions and detection of nitroaromatic explosives

A new luminescent Zn(II)-based metal–organic framework (MOF), [Zn2(TPOM)(NDC)2]·3.5H2O (Zn-MOF; TPOM = tetrakis(4-pyridyloxymethylene)methane and H2ndc = 2,6-naphthalenedicarboxylic acid), was successfully synthesized by a hydrothermal reaction. The MOF exhibits excellent luminescence emission, and it can detect Fe(III) and Cr(VI) ions with high selectivity, well antiinterference performance, and short response time. In addition, Zn-MOF was selected as a parent coordination compound to encapsulate Eu3+ cations to obtain a Eu3+-incorporated sample (Eu3+@Zn-MOF). Subsequently, we explored the potential application of Eu3+@Zn-MOF as a probe for the selective sensing of Fe(III) and Cr(VI) ions, and it revealed that we could differentiate Fe(III) and Cr(VI) ions by the combination Zn-MOF and Eu3+@Zn-MOF. More importantly, it represents the first example of MOF-based luminescent sensors which can detect and differentiate Fe(III) and Cr(VI) ions selectively. And the possible sensing mechanism was discussed in de...

Zinc Metal-Organic Framework for Selective Detection and Differentiation of Fe(III) and Cr(VI) Ions in Aqueous Solution.

Water-soluble and stable CdTe quantum dots (QDs) were synthesized in aqueous solution with glutathione (GSH) as the stabilizer. GSH is employed by nature to detoxify heavy metal ions. As a result of specific interaction, the fluorescence intensity of GSH-capped QDs is selectively reduced in the presence of Cr(VI). Under the optimum conditions, the relative fluorescence intensity decreases linearly with the Cr(VI) concentration in the range from 0.01 to 1.00 µg mL−1, and the detection limit is 0.008 µg mL−1. The luminescence response of the QDs to ions markedly depended on the particle size, and a new strategy for tuning the selectivity of luminescent QDs to certain ions without changing the capping layer of the QDs can be achieved by changing the crystallite size of the QDs.

Simple and sensitive detection method for chromium(VI) in water using glutathione—capped CdTe quantum dots as fluorescent probes

A colorimetric assay is proposed for the selective detection of Cr(III) and Cr(VI) via the aggregation-induced color change of gallic acid capped gold nanoparticles (GA-AuNPs). The AuNPs are characterized using UV-vis spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and Fourier-transform infrared spectrometry (FT-IR). To detect Cr(III) and Cr(VI) coexisting in a sample, citrate and thiosulfate were applied to mask Cr(VI) for the detection of Cr(III), and ethylenediaminetetraacetic acid disodium salt (EDTA) was applied to mask Cr(III) for the detection of Cr(VI). At optimized experimental conditions, the selectivity of these AuNPs-based detection systems is excellent for Cr(III) and/or Cr(VI) compared with other types of metal ions. The limit of detections (LODs) of a mixture of Cr(III) and Cr(VI), Cr(III) and Cr(VI) by eye vision are 1.5, 1.5 and 2 μM, respectively, and those by UV-vis spectroscopy are 0.05, 0.1 and 0.1 μM, respectively. The minimum detectable concentrations for Cr(III) or Cr(VI) are all below the guideline value set by the US Environmental Protection Agency (EPA). The applicability of the AuNPs-based colorimetric sensor is also validated by the detection of Cr(III) and Cr(VI) in electroplating wastewater and real water samples with high recoveries.

Rong Wang

Papers

Rapid determination of chromium(VI) in electroplating waste water by use of a spectrophotometric flow injection system.