Detection Of Cr2O72 Research Articles

Green synthesis of thiadiazole Schiff bases and specific recognition of Cr2O72−, SiO32− and S2−

Sulfide (S2−), silicate (SiO32−) and dichromate (Cr2O72−) ions are prevalent contaminants in industrial effluents, and their rapid and accurate detection is of critical importance for environmental monitoring. In this study, we utilized an environmentally friendly, highly efficient, and biodegradable deep eutectic solvent (DES) to catalyze the synthesis of 2-(((5-phenyl-1,3,4-thiadiazol-2-yl)imino)methyl)phenol (Probe M). Probe M exhibits excellent selectivity for S2−, SiO32− and Cr2O72−, and the corresponding color changes can be readily detected by the naked eye. Upon addition of S2− and SiO32− to the probe solution, the solution turns a distinct orange-red, while the addition of Cr2O72− results in a pronounced darkening of the solution. The detection of S2− and SiO32− by probe M under alkaline condition is stable, and the detection of Cr2O72− under acidic condition is stable. Fluorescence titration experiments revealed that probe M forms a 1:2 stoichiometric complex with S2−, SiO32− and Cr2O72−, with binding constants of 3.84 × 104 M−1, 1.86 × 104 M−1 and 3.19 × 104 M−1, respectively. The detection limits were determined to be 1.76 × 10−4 M for S2−, 9.15 × 10−5 M for SiO32−, and 2.13 × 10−4 M for Cr2O72−. The dipstick experiment demonstrates the probe M can be used as a solid-state sensor to identify S2−, SiO32− and Cr2O72−.

Two MOFs as sensitive and selective sensors for Cr2O72− and glyphosate

A large amount of Cr2O72− and glyphosate (GLYP) discharge cause serious water pollution. In this paper, two new MOFs (Zn‐DPIA and Cd‐DPIA) were synthesized, which have excellent selectivity and sensitivity in the detection of Cr2O72− and GLYP. The detection limits (LODs) of Zn‐DPIA sensing Cr2O72− and GLYP were 1.37 and 1.92 μM, respectively, and the LODs of Cd‐DPIA sensing Cr2O72− and GLYP were 1.19 and 1.42 μM, respectively. Cr2O72− and GLYP detection based on Zn‐DPIA and Cd‐DPIA in tap water is highly reliable based on high recovery rates (97% to 106% and 95% to 103%), indicating that Zn‐DPIA and Cd‐DPIA have practical application prospects.

A Fluorescent g-C3N4 Nanosensor for Detection of Dichromate Ions

Background: Dichromate (Cr2O7 2-) ion is one of the carcinogenic and toxic spices in environment which can easily contaminate the environment due to its high solubility in water. Therefore, a lot of attention has been focused on the detection of Cr2O7 2- with high sensitivity and selectivity. Methods: In present work, nitrogen-rich precursor was used for synthesizing graphitic carbon nitride (g-C3N4) nanostructures through hydrothermal oxidation of g-C3N4 nanosheets. The prepared nanostructures show two distinct fluorescence emissions centered at 368 and 450 nm which are highly sensitive toward Cr2O7 2- ions. Results: The as-prepared g-C3N4 was characterized by several techniques such as Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and fluorescence emission spectra. The XRD pattern of prepared nanostructures illustrated two diffraction patterns (at 13.4° and 27.6°) indicating tri-s-tri-azine-based structures. The g-C3N4 exhibited good selectivity and sensitivity toward Cr2O7 2- among other anions. According to titration test, the detection limit and stern-volmer constant (Ksv) were calculated as 40 nM and 0.13×106 M-1, respectively. The investigation of quenching mechanism shows that Cr2O7 2- may form hydrogen bonding with surface groups of g-C3N4 (such as NH2, OH and COOH) resulted in more fluorescence quenching in comparison with the pure inner filter effect. Conclusion: The g-C3N4 nanostructures were successfully synthesized through the hydrothermal oxidation. The as-prepared g-C3N4 can be used as a highly sensitive fluorescent probe for the selective determination of Cr2O7 2 ion among other anions. The quenching mechanism was experimentally studied. According to reliable responses in real sample tests, it can be proposed that g-C3N4 nanostructure is a suitable sensitive nanosensor for detection of Cr2O7 2 ions in aqueous media.

Cr2O72− inside Zr/Hf-based metal–organic frameworks: highly sensitive and selective detection and crystallographic evidence

The (4,8)-connected Zr/Hf-MOFs exhibit excellent performances in the detection of Cr2O72− and the exact location and configuration of Cr2O72− inside the MOFs were revealed by single-crystal X-ray diffraction studies for the first time.

Structural diversity, magnetic properties, and luminescence sensing based Ni(ii)/Zn(ii) coordination polymers of the semirigid 3,3′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzate ligand

Four novel CPs were synthesized and two Zn(ii)-CPs can be used as fluorescent probes for the detection of CrO42−/Cr2O72−.

Four new metal-organic frameworks based on diverse secondary building units: sensing and magnetic properties.

Four new metal-organic frameworks (MOFs), {[Zn3(L)(OH)(H2O)5]·NMP·2H2O}n (1), {[H2N(Me)2][Zn2(L)(H2O)]·DMF·H2O}n (2), {[Co5(L)2(H2O)11]·2H2O}n (3) and {[Mn5(L)2(H2O)12]·6H2O}n (4), were assembled employing a symmetrical V-shaped rigid multicarboxylic acid ligand H5L (H5L = 2,4-di(3',5'-dicarboxylphenyl)benzoic acid) with different metal ions, resulting in versatile frameworks as well as various types of coordination modes of H5L. 1 forms a three-dimensional (3D) 4-connected sra net based on trinuclear [Zn3(μ3-OH)(μ2-COO)(μ1-COO)4] clusters, while 2 displays a 3D (4,6)-connected net based on two types of binuclear [Zn2(μ2-COO)2(μ1-COO)4] and [Zn2(μ2-COO)4] clusters. 3 and 4 contain similar [M3(μ2-COO)4(μ1-COO)2] (3, M = Co; 4, M = Mn) clusters but result in different 4-connected 3D and 2D frameworks, respectively. 1 and 2 show solid-state luminescence properties at ambient temperature. Meanwhile, 1 shows high selectivity and sensitivity for not only Fe3+ cations but also for CrO42-, Cr2O72- and MnO4- anions via a luminescence quenching effect with a low detection limit, which thus means that it could be a potential crystalline material for detecting these anions. The mechanisms of the quenching effect and sensing properties of 1 are discussed in detail. In addition, 3 and 4 have the presence of antiferromagnetic interactions between the metal ions.

A Multi-responsive Regenerable Europium-Organic Framework Luminescent Sensor for Fe3+ , CrVI Anions, and Picric Acid.

A novel luminescent microporous lanthanide metal-organic framework (Ln-MOF) based on a urea-containing ligand has been successfully assembled. Structural analysis revealed that the framework features two types of 1D channels, with urea N-H bonds projecting into the pores. Luminescence studies have revealed that the Ln-MOF exhibits high sensitivity, good selectivity, and a fast luminescence quenching response towards Fe3+ , CrVI anions, and picric acid. In particular, in the detection of Cr2 O72- and picric acid, the Ln-MOF can be simply and quickly regenerated, thus exhibiting excellent recyclability. To the best of our knowledge, this is the first example of a multi-responsive luminescent Ln-MOF sensor for Fe3+ , CrVI anions, and picric acid based on a urea derivative. This Ln-MOF may potentially be used as a multi-responsive regenerable luminescent sensor for the quantitative detection of toxic and harmful substances.