On the synthesis and performance of a simple colorimetric and fluorescent chemosensor for Cu²⁺ with good...

A colorimetric and fluorescent chemosensor (CS1) for Cu²⁺ based on the mechanism of internal charge transfer (ICT) has been successfully designed and prepared by simple condensation of 4^_(diethylamino)salicylaldehyde and oxalyl dihydrazide. Cu²⁺ in solution (DMSO/H₂O = 7:3, v/v) by 5 mM NaAc-HAc at pH 7.0 was determined through dual channels: (1) "naked-eye" observation, a visually dramatic color change from light green to orange, which can be used for qualitative determination of Cu²⁺; (2) spectrofluorometry, which can quantificationally assay Cu²⁺. It provides a simple-to-use platform for reliable detection of Cu²⁺ at concentrations ranging from 5.0 × 10^-7 to 1.1 × 10^-5 M with detection limit of 1.2 × 10^-7 M, which is nearly 2 × 10² times lower than the maximum allowable level of inorganic Cu²⁺ in drinking water (1.3 ppm, ∼20 µM) permitted by the EPA (Environmental Protection Agency), and the sensing detection of Cu²⁺ ions was reversible.