A novel colorimetric chemosensor for Cu2+ with high selectivity and sensitivity based on Rhodamine B

9-formyl-8-hydroxy-2,3,6,7-tetrahydro-1H, 5H-benzo[ij]-quinolizine rhodamine B hydrazone (FHQRH), a novel colorimetric chemosensor for Cu 2+ , was synthesized by a three-step synthetic route. It was found that FHQRH showed a high selectivity for Cu 2+ ions and excellent anti-interference capability toward other metal ions. The FHQRH solution exhibited a visual color change after the addition of Cu 2+ , owing to the open spirocyclic structure via coordination with Cu 2+ . The complexation coefficient of FHQRH toward Cu 2+ was measured to be 1:1. Furthermore, this Cu 2+ chemosensor has a remarkable low detection limit of 0.45 μM, which is 2 % of the toxic level (20 μM) in drinking water as defined by the US Environment Protection Agency (EPA).