Curcumin/beta-cyclodextrin inclusion complex as a new "turn-off' fluorescent sensor system for sensitive recognition of mercury ion

The formation of supramolecular complex between the curcumin (CC or probe L) and beta-cyclodextrin CD) (CC: beta-CD or probe LC) was confirmed using absorption and emission spectroscopy. The binding properties of probe LC with cations in water were observed for the first time via absorption and emission spectroscopies. The selectivity and sensitivity of fluorescence chemosensors have been studied using probe LC. The probe LC showed selective binding to Hg2+ and afforded new absorbance and fluorescence peaks at 379 nm and 502 nm, additionally to the prevailing bands of LC at 432 nm and 535 nm. It additionally showed apparent color change from yellow to colourlessness and strong fluorescent to weak fluorescent owing to selective binding of Hg2+ ion, which was detected by naked eyes. No noticeable changes of color and spectra were observed upon the addition of other metal cations such as [Ag+, K+, Na+, Cs+, Ba2+, Pe(2+), Mg2+, Pb2+, Mn2+, Ni2+, Cd2+, CO2+, Cr3+, Sn2+ and Zn2+. Hg(2+ )produced blue shift in absorption spectra and quenching in emission spectra which suggested a likelihood of strong binding of Hg2+ ions with probe LC. The fluorescence response was concentration-dependent and can be well described by the typical Stern-Volmer model. Compared with prior reports, this method is very cheap, selective, sensitive and easily biodegradable of probe LC. (C) 2019 Elsevier B.V. All rights reserved.