Highly sensitive and selective optical chemosensor for determination of Cu2+ in aqueous solution

A highly selective and sensitive rhodamine-based colorimetric chemosensor (1) for quantification of divalent copper in aqueous solution has been investigated in this work. It was designed using salicylaldehyde hydrazone and rhodamine 6G as copper-chelating and signal-reporting groups, respectively. In environmentally friendly media (50%(v/v) water/ethanol and 10mM NaAc-HAc neutral buffer (pH 7.0)), the sensor exhibited selective absorbance enhancement to Cu(2+) over other metal ions at 529 nm, with a dynamic working range of 0.05-5.00 microM and a detection limit of 10nM Cu(2+), respectively. To achieve fluorometric determination of Cu(2+), the Cu(2+)-induced absorbance enhancement of 1 was efficiently converted to fluorescence quenching by fluorescence inner filter effects using rhodamine B (RB) as a fluorophore. The selectivity and sensitivity of fluorescence analysis were similar to those of absorptiometric measurement. Both absorptiometric and fluorometric methods were successfully applied to the detection of Cu(2+) in three water samples.