A highly sensitive and selective “off–on” chemosensor for the visual detection of Pd2+ in aqueous media

A naked-eye “off–on” fluorescent probe (1) was synthesized by rhodamine B hydrazide and p-dimethylaminobenzaldehyde, which showed highly selective recognition toward Pd2+ over other examined metal ions. Upon addition of Pd2+, sensor 1 exhibits enhanced fluorescence intensity and UV–vis spectrum in aqueous solution. The sensor 1 was also successfully applied to determination of Pd2+ in palladium-containing catalyst and water samples.