Yu Jeong Na

A single colorimetric sensor for multiple target ions: the simultaneous detection of Fe2+ and Cu2+ in aqueous media

This study demonstrates the design, synthesis and sensing properties of a simple and efficient chemosensor 1 (1 = 2,6-bis((2-(((pyridine-2-yl)methylamino)methyl)phenol)ethylamido)pyridine) to rapidly detect Fe2+ and Cu2+ in aqueous solution (bis-tris buffer/DMF (8/2, v/v)), exploiting UV-vis spectral analysis, naked-eye and paper devices. The sensor 1 showed significant absorption spectra at 455 nm for Fe2+ and 660 nm for Cu2+, which are responsible for color changes due to the metal-to-ligand charge-transfer. The binding modes of 1 with Fe2+ or Cu2+ have been investigated by Job plot and ESI-mass analysis. In addition, the sensor 1 could be recyclable simply through treatment with a proper reagent such as EDTA. Moreover, the sensor has been used in the development of practically viable colorimetric kits.

A diaminomaleonitrile based selective colorimetric chemosensor for copper(II) and fluoride ions

A new and simple colorimetric receptor 1, based on 2,3-diaminomaleonitrile and julolidine moieties, has been synthesized and characterized. 1 showed a selective colorimetric sensing ability for copper(II) ions by changing color from yellow to colorless, and could be utilized to monitor Cu2+ over a wide pH range of 4–12. The detection limit of 1 (2.1 μM) for Cu2+ ions is much lower than that recommended by WHO in drinking water (30 μM). Moreover, the receptor 1 can also detect fluoride by color change from yellow to orange, distinguishing the fluoride ions effectively from anions such as CH3COO− and CN−. It was also found that the 1–F− complex was reversibly bound and could be simply reverted back through treatment with a proper reagent such as HCl. The sensing mechanism for F− was theoretically supported by DFT and TD-DFT calculations.

Dual-channel detection of Cu2+ and F− with a simple Schiff-based colorimetric and fluorescent sensor

A simple and easily synthesized colorimetric and fluorescent receptor 1, based on 4-diethylaminosalicylaldehyde moieties as a binding and signaling unit, has been synthesized and characterized. The receptor 1 has a selective colorimetric sensing ability for copper (II) ion by changing color from colorless to yellow in aqueous solution, and could be utilized to monitor Cu(II) over a wide pH range of 4-11. In addition, the detection limit (12μM) of 1 for Cu(2+) is much lower than that (30μM) recommended by WHO in drinking water, and its copper complex could be reversible simply through treatment with a proper reagent such as EDTA. Moreover, receptor 1 exhibited both a color change from colorless to yellow and fluorescence enhancement with a red shift upon addition to F(-) in DMSO. The recognition mechanism was attributed to the intermolecular proton transfer between the hydroxyl group of the receptor and the fluoride.

A single chemosensor for multiple analytes: fluorogenic detection of Zn2+ and OAc− ions in aqueous solution, and an application to bioimaging

A new highly selective and sensitive chemosensor 1 for both Zn2+ and OAc− with off–on fluorescence behavior in aqueous solution was developed. The selectivity mechanism of 1 for zinc is based on a combinational effect of the inhibition of excited-state intramolecular proton transfer and CN isomerization, and chelation-enhanced fluorescence. As a practical application, in vitro studies with fibroblasts showed fluorescence in the presence of both the receptor 1 and Zn2+. Moreover, the deprotonated 1 can behave as a chemosensing system for turn-on detection of OAc− in preference over various other anions tested. Therefore, 1 can serve as ‘one sensor for multiple analytes’.

A colorimetric chemosensor based on a Schiff base for highly selective sensing of cyanide in aqueous solution: the influence of solvents

A new highly selective colorimetric chemosensor 1 (E)-9-(((2-hydroxy-5-nitrophenyl)imino)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol for CN− was developed. Receptor 1 showed exclusive response toward cyanide by a color change in aqueous solution. However, in aprotic solvents and methanol, the unique selectivity of 1 for CN− disappeared, and its nonselective color change was observed for other anions. This phenomenon could be possibly explained by the combination of the basicity and the hydrogen bonding ability of the anions. Moreover, 1 could be used as a practical, visible colorimetric test kit in an aqueous environment.

Selective fluorescence assay of aluminum and cyanide ions using chemosensor containing naphthol

The selective assay of aluminum and cyanide ions is reported using fluorescence enhancement and quenching of a phenol–naphthol based chemosensor (PNI) in aqueous and nonaqueous solvents, respectively. PNI gave no significant fluorescence in water. The binding properties of PNI with metal ions were investigated by UV-vis, fluorescence, and electrospray ionization mass spectrometry in a Bis–Tris buffer solution. The addition of aluminum ions switches on the fluorescence of the sensor PNI in water, comparable to relatively very low fluorescence changes in the presence of various other metal ions. The complex stability constant (Ka) for the stoichiometric 1 : 1 complexation of PNI with aluminium ions was obtained by fluorimetric titrations and NMR experiments. However, upon treatment with cyanide ions, the fluorescence of PNI was selectively turned off and the yellow solution of PNI turned to red in methanol. Other comparable anions, such as F−, Cl−, Br−, I−, CH3COO−, and H2PO4−, afforded no apparent fluorescence quenching. The interaction of PNI with cyanide ions was studied by NMR experiments.

A selective colorimetric chemosensor with an electron-withdrawing group for multi-analytes CN− and F−

A new colorimetric chemosensor with an electron-withdrawing group (–NO2) 1 for the detection of CN− and F− has been simply developed. Receptor 1 showed selectively colorimetric responses to CN− in aqueous solution and F− in acetonitrile, respectively. An obvious color change of 1 from yellow to colorless was observed for CN− through a nucleophilic addition mechanism, while F− was detected through a deprotonating mechanism with a distinct color change from pale yellow to orange. The binding modes of receptor 1 with two analytes (CN− and F−) were proposed to be 1 : 1, based on the Job plot, 1H NMR titration, and ESI-mass spectrometry analysis.