Pyridoxal-Based Selective Chemo Sensor for Colorimetric and Fluorescent Detection of Copper Ions and Imaging in Live Cells

A novel pyridoxal-based chemo sensor (PDBI) was synthesized, characterized and demonstrated for the detection of Cu²⁺ ions. The sensing ability of the chemo sensor was assessed in a 10% DMSO-HEPES pH 7.4 buffer medium using both fluorescence and colorimetric methods. PDBI exhibited greater binding affinity and selectivity for Cu²⁺ by showing a fluorescence ON-OFF phenomenon and colorimetric response from yellow to brown. The limit of detection of PDBI to Cu²⁺ was calculated to be 28 nM. The stoichiometric ratio of Cu²⁺ to PDBI in the complex is 1:1, as indicated by the job’s plot. The chelation mechanism was supported by partial ¹H-NMR, HRMS and quantum chemical calculations. PDBI was converted into portable paper strips for the detection of Cu²⁺ in real samples, and also enabled the detection of copper in live cells.