Satheshkumar Angupillai, Ji-Yong Hwang, Jae Young Lee
Jul 31, 2015
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Journal
Sensors and Actuators B-chemical
Abstract
Abstract This paper describes the optimized design, synthesis and application of three novel thiosemicarbazide-appended rhodamine spirolactam derivatives as ‘turn-on’ colorimetric and fluorescent chemodosimeters ( 1 – 3 ) for the detection of Hg 2+ in aqueous samples with a broad pH range (5.0–9.4). The ‘turn-on’ change in the color and fluorescence signals of 1 – 3 is based on a Hg 2+ -triggered reaction that converts the thiosemicarbazide form to the 1,3,4-oxadiazole form. The results of 13 C NMR studies indicated that the basicity of the ‘C S’ can be varied from δ 183.05 (for nitro) to 181.3 ppm (for methyl) by changing the R group in the chemodosimeter. Electronic and spectrofluorimetric studies indicated that the order of the binding constants of these chemodosimeters with Hg 2+ ions is 1 > 2 > 3 , which may be dependent on the substituent. Chemodosimeters 1 – 3 exhibit a stable response to Hg 2+ from 2.5 × 10 −7 to 2.0 × 10 −5 M with a detection limit of 10 −8 M. The response of these chemodosimeters to Hg 2+ is highly selective and pH insensitive, and the response time is rapid. All of these unique features make these sensors particularly favorable for Hg 2+ test strip applications. These sensors have been preliminarily used for the highly sensitive monitoring of Hg 2+ levels in aqueous media with satisfactory resolution.