The natural compound chrysosplenol-D is a novel, ultrasensitive optical sensor for detection of Cu(II)

Abstract Herein, we introduce a novel, ultrasensitive optical sensor for determination of Cu(II) ions over the concentration range of 0 to 1 μM Cu(II). The optical sensor is based on the natural molecule chrysosplenol-D (Chp-D) extracted from the flowering plant Chiliadenus montanus (Vahl.) Brullo. Free Chp-D emits fluorescence at 566 nm when excited at 292 nm. Chp-D chelates Cu(II) ions to form a 1:1 (metal:ligand) complex, which quenches the fluorescence emission peak of the free probe at 566 nm. “Turn-off” luminescence could be easily determined and provided distinct proof of the chelation of Cu(II) ions by Chp-D. This novel optical sensor offers a considerable fluorescence mechanism (charge transfer complex, CTC). Chp-D is an extremely sensitive and selective optical sensor for Cu(II) ions, with distinctive fluorescence properties, a large Stokes shift of ~275 nm and recognition aptitude. Moreover, Chp-D has low limit of detection (LOD) for Cu(II) of 1.2 × 10−8 M in buffered media at physiological pH (pH 7.4), a linear range of 0.04 to 1.0 μM and a relative standard deviation (RSDr) of 1% (n = 3). Furthermore, this natural probe has a high binding affinity for Cu(II), with a binding constant of 3.36 × 108 M−1. Overall, we propose Chp-D represents a novel, natural optical sensor for the detection of Cu(II).