Discriminating Cr(III) and Cr(VI) using aqueous CdTe quantum dots with various surface ligands

The discrimination of Cr(III) and Cr(VI) is considered as one of the important analytical issues for environmental protection and disease prevention, because Cr(III) and Cr(VI) have different physiological effects and toxicities. Low cost, highly sensitive fluorescent sensors are highly demanded. Herein we report a facile and feasible method for discriminating Cr(III) and Cr(VI) by employing the aqueous CdTe quantum dots (QDs) with different surface ligands by virtue of their difference in quenching QD fluorescence. The QD fluorescence quenching by Cr(III)/Cr(VI) is mainly affected by electrostatic interaction, which is greatly determined by the surface functionalities of QDs. Thus, by combining the different fluorescence quenching behavior of carboxyl-, hydroxyl-, and/or amino-functionalized QDs, Cr(III) and Cr(VI) are discriminated. In comparison to the discrimination using the QDs with single surface functionality, the current method indicates improved reliability and accuracy.