Highly Sensitive and Selective Porphyrin-Based Fluorescent Probe for Nanomolar Detection of Cu²⁺ Ions

Copper is an indispensable trace element for maintaining metabolic homeostasis; however, the dysregulation and subsequent accumulation of Cu²⁺ are critically linked to neurodegenerative pathologies, including Alzheimer’s disease in humans. Consequently, the development of robust analytical tools for Cu²⁺ monitoring is of paramount importance. Here, we report a 2,2′-dipicolylamine porphyrin (DPAP) based fluorescent sensor designed for the precision detection of metal cations. Photophysical investigations reveal that DPAP operates via a rapid turn-off fluorescence mechanism, achieving high-performance sensing in the parts-per-million range. Notably, the probe demonstrates exceptional sensitivity with a detection limit of 30.3 nM for Cu²⁺ and 34.8 nM for Ni²⁺. Interference studies further confirm the superior selectivity of DPAP for Cu²⁺ over a broad spectrum of competing metal ions. These findings highlight DPAP as a simple, yet highly sensitive and selective probe for environmental monitoring and biomedical diagnostics involving copper ions.