Amino-coumarin-based colorimetric and fluorescent chemosensors capable of discriminating Co2+, Ni2+, and Cu2+ ions in solution and potential utilization as a paper-based device.

New chemosensors, L1-L3, based on the coumarin Schiff base scaffold with substituent modifications, have been designed and synthesized. The chemosensors L1-L3 exhibited the absorbance and fluorescence spectral changes that can discriminate Co2+, Ni2+, and Cu2+ ions. Sensor L1 demonstrated the ability to respond to Co2+, Ni2+, and Cu2+ ions. Remarkably, the slight modification of substituent on L2 has been observed to cause selective binding to Ni2+ and Cu2+ ions while L3 can specifically detect Cu2+ ions. The in-situ formation of metal and ligand complexes was determined by Job's plot analysis. The limit of detection and the sensing ability of all probes are estimated to be within the range of safe drinking water. Incorporation of the sensing compounds into a paper-based detection system using a laminated paper-based analytical device (LPAD) was demonstrated and found to be consistent to those obtained from the batchwise solution measurements.