New colorimetric chemosensor bearing naphthalendiimide unit with large blue-shift absorption for naked eyes detection of Cu2+ ions

A naphthalendiimide-based chemosensor was designed for naked-eye detection of Cu2+, which displayed high selectivity in the presence of other competitive metal ions. The Cu2+ recognition gave rise to apparent red-to-yellow color change with the blue-shift maximum absorption wavelength as large as 80 nm, through the intramolecular charge transfer mechanism. The pH effect studies indicated that it can be applied to the analysis of samples from mildly acidic to basic environments.