Cascade Detection of Pyridoxal 5′-Phosphate and Al³⁺ Ions Based on Dual-Functionalized Red-Emitting Copper Nanoclusters

Pyridoxal 5′-phosphate (PLP), a biologically important coenzyme, participates in several enzymatic reactions, and its marginal deficiency in the human body can cause cardiovascular disease. However, the excess accumulation of the non-essential Al³⁺ metal ion in the human body can also cause serious health problems. Therefore, there is significant interest in the detection and monitoring of both PLP and Al³⁺. This paper introduced a red-emitting dual-ligand co-functionalized copper nanoclusters β-CD-GSH-CuNCs for the simultaneous detection of PLP and Al³⁺. The capped β-cyclodextrin (β-CD) in β-CD-GSH-CuNCs selectively recognizes PLP by forming a host–guest inclusion complex that caused fluorescence quenching at 625 nm with the formation of an emission band at 488 nm. The ratiometric fluorescence from β-CD-GSH-CuNCs allowed to detect PLP down to 5.29 μM. Further, the in situ-generated nano-assembly β-CD-GSH-CuNCs@PLP showed a selective turn-on fluorescent response for Al³⁺. The complexation-induced aggregation of nano-assembly resulted in strong fluorescence enhancement at 451 nm that allowed to detect Al³⁺ down to 0.187 μM. The analytical utility of β-CD-GSH-CuNCs@PLP was validated as a nanoprobe by monitoring Al³⁺ concentrations in real environmental water samples.