Simple hydrazide-based fluorescent sensors for highly sensitive and selective optical signaling of Cu2+ and Hg2+ in aqueous solution

Two new water-soluble hydrazide-based fluorescent probes of poly 3-{[1-(2-hydrazino-2-oxoethyl)piperidin-4-ylidene[methyl}thiophene hydrochloride (PM1 center dot HCl) and poly 3-{[1-(3-hydrazino-3-oxopropyl)piperidin-4-ylidene[methyl}thiophene hydrochloride (PM2 center dot HCl) have been designed and synthesized. PM1 center dot HCl selectively recognizes Cu2+ and Hg2+ in aqueous solution with different emission characteristics (blue-shifted for Cu2+ and red-shifted for Hg2+) and color changes, and the color response of the sensory materials can be tuned for detection with the naked eye. Detection limits of sensor PM1 center dot HCl for Cu2+ and Hg2+ were estimated to be 2.0 x 10(-10) M and 2.0 x 10(-9) M, respectively. Fluorescence sensor PM2 center dot HCl also showed high sensitivity toward Cu2+ in aqueous media, and the detection limit was measured to be as low as 2.0 10(-10) M. Upon addition of Hg2+ to the PM2 center dot HCl aqueous solution, no significant changes of the fluorescence spectra were observed. (C) 2013 Elsevier B.V. All rights reserved.