A rhodamine-based dual chemosensor for the visual detection of copper and the ratiometric fluorescent detection of vanadium

The optical properties of a novel, rhodamine-based derivative, synthesized by reacting rhodamine hydrazide and 5-chlorosalicylaldehyde in ethanol, were investigated in methanol:HEPES solution. The novel sensor displayed selectivity for Cu2+, as evidenced by a colourless to dark red colour change, which was characterized using UV–visible spectroscopy and which also allowed visual detection of Cu2+. In contrast, selectivity towards VO2+ was determined from changes in the emission spectra in the nanomolar range. This represents the first reported rhodamine-based sensor capable of detecting both Cu2+ and VO2+ using two different modes.