Seul Ah Lee

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.

A highly selective CHEF-type chemosensor for monitoring Zn2+ in aqueous solution and living cells

A new simple quinolone-based chemosensor 1 was synthesized for Zn2+. 1 exhibited selective fluorescence enhancement in the presence of Zn2+ with a 1 : 1 stoichiometry in aqueous solution, which was reversible with the addition of ethylenediaminetetraacetic acid (EDTA). The detection limit (0.019 μM) of 1 for Zn2+ is far lower than the World Health Organization guideline (76 μM) in drinking water. 1 was successfully applied to quantify and image Zn2+ in water samples and living cells. The sensing mechanism of Zn2+ by 1 via the chelation-enhanced fluorescence (CHEF) effect was supported by theoretical calculations. Therefore, 1 could be used in a practical system for monitoring Zn2+ in aqueous solution.

A colorimetric chemosensor for the sequential detection of copper ion and amino acids (cysteine and histidine) in aqueous solution

A simple and selective colorimetric chemosensor 1 was reported for the sequential detection of Cu2+, cysteine (Cys) and histidine (His) in aqueous solution. The presence of Cu2+ led to a distinct naked-eye color change from pale yellow to orange. Also, the receptor enabled analysis of Cu2+ ions with a sensitivity limit of 0.37 μM, which is far below the WHO acceptable limit (31.5 μM) in drinking water. 1 could be also used as a practical, visible colorimetric test strip for Cu2+ (down to 10 μM) in aqueous media. Moreover, the resulting 1–Cu2+ complex sensed cysteine and histidine with an absorption change via UV-visible or a naked-eye color change, although His and Cys were indistinguishable with the method proposed herein.

Distinction between Mn(III) and Mn(II) by using a colorimetric chemosensor in aqueous solution

A new colorimetric chemosensor for Mn(III) and Mn(II) was developed by combination of 2-(aminomethyl)aniline and 4-(diethylamino)-2-hydroxybenzaldehyde. This sensor 1 exhibited an obvious color change from pale yellow to reddish brown in the presence of Mn3+ in aqueous solution (buffer/CH3CN = 7 : 3), which was reversible with the addition of EDTA. Moreover, 1 could be used to detect and quantify Mn3+ in water samples, and as a practical, visible colorimetric test kits for Mn3+. Moreover, 1 could detect Mn2+ via the formation of 1–Mn3+ complex with longer reaction time. The resulting different reaction time of Mn(III) and Mn(II) with 1 was used to differentiate between Mn(III) and Mn(II). Finally, the sensing ability of 1 for Mn3+ was supported by theoretical calculations.