Seong Youl Lee

Multiple target chemosensor: a fluorescent sensor for Zn(II) and Al(III) and a chromogenic sensor for Fe(II) and Fe(III)

A multifunctional fluorescent and colorimetric chemosensor 1, based on two julolidine moieties as a binding and signaling unit, has been synthesized in a one-step procedure. Receptor 1 showed prompt responses toward Zn2+ and Al3+ ions through selective fluorescence enhancement in dimethylformamide (DMF), while the presence of 5% water made 1 detect only Zn2+. Moreover, with 1 the “naked eye” could sense iron by a clear color change. Upon the addition of Fe2+ and Fe3+ into each solution of 1, the color of the solutions changed from pale yellow to dark green for both Fe2+ and Fe3+. The binding modes of the complexes were determined to be a 1:1 complexation stoichiometry from a Job plot, 1H NMR titration and ESI-mass spectrometry analysis.

Highly selective and sensitive colorimetric chemosensor for detection of Co2+ in a near-perfect aqueous solution

A new simple and easy-to-make colorimetric chemosensor 1 was designed and synthesized by combination of 4-diethylaminosalicylaldehyde and diethylenetriamine. In a near-perfect aqueous solution, sensor 1 showed a selective color change from colorless to yellow in the presence of Co2+ with a 1 : 1 stoichiometric system. To investigate the sensing mechanism of 1 for Co2+, UV-vis spectroscopy, ESI-mass and theoretical calculations were conducted. The detection limit (0.65 μM) of 1 for Co2+ was comparable to the Federal-State Toxicology and Risk Analysis Committee (FSTRAC) guideline in drinking water (0.68 μM). Practically, 1 functioned as a visible test strip with a silica plate and could be used to quantify Co2+ in real water samples. Therefore, probe 1 could be a good alternative method for on-site and real time screening of Co2+.

A colorimetric chemosensor for sulfide in a near-perfect aqueous solution: practical application using a test kit

A new highly selective colorimetric chemosensor 1 N′1-((E)-2,3-dihydroxybenzylidene)-N′2-((Z)-2,3-dihydroxybenzylidene)oxalohydrazide for S2− was designed and synthesized. The sensor 1 showed a selective colorimetric sensing ability toward S2− by changing color from colorless to yellow in a near-perfect aqueous solution. To understand the sensing mechanism of 1 with S2−, UV-vis spectroscopy, ESI-mass spectroscopy analysis and DFT calculations were carried out. Practically, sensor 1 functioned as a visible test strip for S2−. Moreover, the sensing ability of 1 for S2− was successfully applied in real water samples. Therefore, sensor 1 could be a good alternative method for onsite and real time screening of S2−.

A fluorescence “turn-on” chemosensor for Hg2+ and Ag+ based on NBD (7-nitrobenzo-2-oxa-1,3-diazolyl)

A new fluorescent sensor 1 was prepared by bridging a 7-nitrobenzo-2-oxo-1,3-diazolyl (NBD) fluorophore with a dimethyl ethylene amine group via an ethylamine spacer. Distinct “turn-on” fluorescence changes of 1 were observed upon the addition of Hg2+ and Ag+ in the aqueous solution. The sensor 1 showed high sensitivity toward Hg2+ and Ag+ with detection limits of 0.05 μM and 0.12 μM, respectively. Moreover, the sensing abilities of 1 for Hg2+ and Ag+ were successfully carried out in real water samples, and 1 functioned as fluorescent test strip with silica plate. The sensing mechanisms of 1 with Hg2+ and Ag+ were studied by using photophysical experiments, NMR titration, and ESI-mass spectrometry analysis. Moreover, turn-on fluorescence of 1 toward Hg2+ and Ag+ caused by photo-induced electron transfer (PET) was explained by density functional theory (DFT) calculations.

Colorimetric detection of Fe3+/2+ and fluorescent detection of Al3+ in aqueous media: applications and DFT calculations

Abstract A new multifunctional colorimetric and fluorescent chemosensor 1 for Fe3+/2+ and Al3+ has been synthesized in the one-step procedure. The sensor 1 detected both Fe2+ and Fe3+ through the color change from yellow to brown and Al3+ via turn-on fluorescence. The binding stoichiometries of sensor 1 with Fe3+/2+ and Al3+ were proposed to be 1:1 with the analyses of ESI-mass and Job plot. Importantly, the detection limits of 1 for Fe3+/2+ (2.11 and 2.70 μM) and Al3+ (3.44 μM) were lower than the EPA guideline (5.37 μM) for Fe3+/2+ and WHO guideline (7.41 μM) for Al3+. Compound 1 was used to quantify ferric species (Fe3+) in real samples. Moreover, the sensing processes for Fe3+/2+ and Al3+ were proposed with the spectroscopic studies and theoretical calculations.