A Chromo-Fluorogenic Naphthoquinolinedione-Based Probe for Dual Detection of Cu and Its Use for Various Water Samples.

The presence of an abnormal amount of Cu in the human body causes various health issues. In the current study, we synthesized a new naphthoquinolinedione-based probe (probe ) to monitor Cu in different water systems, such as tap water, lakes, and drain water. Two triazole units were introduced into the probe via a click reaction to increase the binding affinity to a metal ion. In day-light, probe dissolved in a mixed solvent system (HEPES: EtOH = 1:4) showed a vivid color change from light greenish-yellow to pink in the presence of only Cu among various metal ions. In addition, the green luminescence and fluorescence emission of the probe were effectively bleached out immediately after Cu addition. The limit of detection (LOD) of the probe was 0.5 µM when a ratio-metric method was used for metal ion detection. The fluorescence titration data of the probe with Cu showed a calculated LOD of 41.5 pM. Hence, probe possesses the following dual response toward Cu detection: color change and fluorescence quenching. Probe was also useful for detecting Cu spiked in tap/lake water as well as the cytoplasm of live HeLa cells. The current system was investigated using ultraviolet-visible and fluorescence spectroscopy as well as density functional theory calculations (DFT).