A colorimetric probe for detection of Cu2+ by the naked eye and application in test paper

A novel colorimetric probe RP1 was synthesized using rhodamine derivatives and heterocyclic compounds for the purpose of detecting Cu2+. RP1 showed good selectivity, high sensitivity and affinity toward Cu2+ over other competing ions in CH3OH–H2O (1/1, v/v) solution. Absorbance intensity showed a good linear fit between probe R1 and Cu2+ over the concentration range 1–8 μM and the association constant was also calculated to be 1.145 × 105 M−1. The sensing mechanism was deduced using Job's plot, Fourier transform infrared spectroscopy, and density functional theory studies. In addition, the colorimetric experiment indicated that probe RP1 could be made into test paper to detect Cu2+ with a colour change from colourless to pink.