Simultaneous detection of Cu2+ and Cr3+ by a simple Schiff-base colorimetric chemosensor bearing NBD (7-nitrobenzo-2-oxa-1,3-diazolyl) and julolidine moieties

A new NBD (7-nitrobenzo-2-oxa-1,3-diazolyl) and julolidine-based chemosensor 1 was designed and synthesized as a colorimetric chemosensor for Cu2+ and Cr3+. The presence of Cu2+ and Cr3+ led to distinct visible color changes from violet to yellow and blue, respectively, in aqueous solution. To examine the binding mechanisms of 1 with Cu2+ and Cr3+, UV-vis spectroscopy, ESI-mass spectrometry analysis and DFT calculations were conducted. The detection limits for the analysis of Cu2+ and Cr3+ ions were found to be 0.36 μM and 0.59 μM, respectively. Practically, sensor 1 functioned as a visible test strip for Cu2+ and Cr3+. Moreover, the sensing abilities of 1 for Cu2+ and Cr3+ were successfully carried out in real water samples. Therefore, sensor 1 can be employed as a practical colorimetric chemosensor for detecting both Cu2+ and Cr3+.

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