Rhodamine-based derivatives for Cu2+ sensing: spectroscopic studies, structure-recognition relationships and its test strips.

A rhodamine spirolactam/2-hydrazinopyridine derivative was synthesized and characterized, which exhibited high selectivity to Cu(2+) over other metal cations. The Cu(2+) recognition of this rhodamine derivative could be detected by fluorescence spectra, absorption spectra and an obvious color change which was observed easily by naked-eyes. The binding of this rhodamine derivative to Cu(2+) is instantaneous and sensitive. Moreover, a linear relationship was found between the fluorescence intensity at 575 nm from 0.5×10(-6) M to 3.0×10(-6) M of Cu(2+) concentration, and the limit of detection (LOD) was at low concentration of 2.11×10(-8) M, this would benefit for the establishment of standard working curves in practical Cu(2+) detection. Additionally, we synthesized rhodamine spirolactam/2-aminomethylpyridine derivative and rhodamine spirolactam/phenylhydrazine derivative as analogs for elucidate the structure-recognition relationships. Finally, we prepared the test strips of rhodamine spirolactam/2-hydrazinopyridine derivative for practical chromogenic the Cu(2+) detection.