Dye functionalized lanthanide metal-organic framework as a multifunctional luminescent hybrid material for visual sensing of biomarker 2-methoxyaceticacid and sulfide anion

Based on the anionic Slug-47 [Gd(bpdc)₂^-] [NH₂(CH₃)₂⁺], a multifunctional fluorescent material with ultra-high stability has been fabricated successfully. Firstly, Eu_0.04Tb_39.96Gd₆₀ with white light emission is prepared by adjusting the doping ratio of Eu³⁺ ions and Tb³⁺ ions. Then, the dye acriflavine (ACF) is further introduced into the framework of Eu@ Slug-47 (1) via cation exchange to obtain ACF@1, which can be used as a ratio fluorescence sensor to detect 2-methoxyaceticacid (Maa), a toxic metabolite of glycol monomethyl ether, with the limit of detection (LOD) as low as 0.27 μg/mL. It is impressive that the emissions of ACF and biphenyl-4,4'-dicarboxylicacid ligands are gradually enhanced with the gradual weakening of the emission of Eu³⁺ ions during the detection of Maa. Under the superposition of three different colors, the sensing process undergoes a distinct color change from red to white and then to blue. These rich and colorful colors provide conditions for accurate visual detection of Maa. In addition, the material can also respond well to the pollutant S^2- ions and the LOD can reach 11.3 μmol /L. It is worth mentioning that the available quenching effect can be observed even if Maa and S^2- ions are detected in urine and tap water respectively, indicating that the multifunctional material has a brilliant application prospect. Finally, the quenching mechanism of Maa, S^2- ions toward ACF@1 is discussed in detail.

A paper-based colorimetric chemosensor for rapid and highly sensitive detection of sulfide for environmental monitoring

In this study, we report on paper-based colorimetric detection of sulfide using a newly synthesized chemical acting as a chemosensor, based on the deprotonation mechanism. Paper strips were also fabricated and incorporated with the chemosensor for on-site monitoring. The presence of sulfide induced deprotonation of a hydroxyl group of the chemosensor, which eventually resulted in a distinct spectral change in the tube as well as a visible color change on a paper strip. The chemosensor showed a highly selective colorimetric response to sulfide by changing its color from colorless to yellow without any interference from a mixture containing other anions. Moreover, the chemosensor effectively differentiated sulfide from other thiols, including cysteine and glutathione. The chemosensor colorimetrically detected sulfide with a fast response time of 10 s under physiological conditions. Practically, the paper test strip enabled colorimetric visualization of as low as 30 μM sulfide and a good recovery in quantitative analysis in water samples. The introduced paper-based chemosensor is a promising colorimetric strategy with rapid, selective, and sensitive sensing abilities for sulfide monitoring in environmental water samples.

A nano-molar level fluorogenic and oxidation state-selective chromogenic dual reversible chemosensor for multiple targets, Cu2+/S2− and Fe3+/F− ions

A pyridine–pyrazole–pyrene-based multipurpose chemosensor has been introduced which has been found to exhibit excellent luminescent and optical properties.

An Imidazo[1,5-α]Pyridine-Based Fluorometric Chemodosimeter for the Highly Selective Detection of Hypochlorite in Aqueous Media

A new fluorometric chemodosimeter 2-amino-3-(((E)-3-(1-phenylimidazo[1,5-α]pyridin-3-yl)benzylidene)amino)maleonitrile (BPI-MAL) has been designed and synthesized for sensing hypochlorite. BPI-MAL showed a selective turn-on fluorescence for ClO^- through hypochlorite-promoted de-diaminomaleonitrile reaction. It also could detect ClO^- in the presence of various competitive anions including reactive oxygen species. Interestingly, sensor BPI-MAL was successfully applied as a fluorescent test kit for ClO^- determination. The sensing property and mechanism of BPI-MAL toward ClO^- were studied by fluorescence and UV-vis spectroscopy, NMR titration and DFT calculations.

A new Schiff-base chemosensor for selective detection of Cu2+ and Co2+ and its copper complex for colorimetric sensing of S2- in aqueous solution

A new Schiff-base colorimetric chemosensor 1 was developed for the detection of Cu²⁺, Co²⁺ and S^2-. Sensor 1 could simply monitor Cu²⁺ and Co²⁺ by a color change from colorless to yellow. The binding modes of 1 to Cu²⁺ and Co²⁺ were determined to be a 2 : 1 complexation stoichiometry through Job's plot and ESI-mass spectrometry analysis. The detection limits (0.02 μM and 0.63 μM) for Cu²⁺ and Co²⁺ were lower than the recommended values (31.5 μM and 1.7 μM) by the World Health Organization (WHO) for Cu²⁺ and the Environmental Protection Agency (EPA) for Co²⁺, respectively. Importantly, 1 could detect and quantify Cu²⁺ in real water samples. In addition, the Cu²⁺-2·1 complex could be used as a highly selective colorimetric sensor for S^2- in the presence of other anions without any interference. Moreover, the sensing mechanisms of Cu²⁺ and Co²⁺ by 1 were explained by theoretical calculations.