Anthraquinone-based turn-on fluorescence probe for selective and sensitive detection of Cu²⁺ ions

A novel anthraquinone-hydrazone fluorescent probe (AFSA) was designed and synthesized for the selective and sensitive detection of Cu²⁺ ions, which is of great significance for environmental heavy metal monitoring.

The sensing performance of AFSA was systematically investigated in an EtOH/H₂O (5:1, V/V) binary solution system. Its molecular structure was characterized using multiple spectroscopic techniques, and theoretical spectral properties were further calculated via the GaussView 9.0 quantum chemical program. The binding stoichiometry between AFSA and Cu²⁺ was determined using Job's continuous variation method.

AFSA exhibited a distinct turn-on fluorescence response toward Cu²⁺, with a detection limit of 0.86 μM at 766 nm and a response time of less than 1 min. The fluorescence emission remained stable over a wide pH range of 5.0-11.0. Selectivity assays demonstrated negligible interference from common coexisting metal ions, including Al³⁺, Ba²⁺, Ca²⁺, Co²⁺, Hg²⁺, Fe³⁺, K⁺, Mn²⁺, Na⁺, Ni²⁺, Pb²⁺, and Zn²⁺.

The above results indicate that AFSA is a promising fluorescent probe for Cu²⁺ detection with excellent selectivity, high sensitivity and favorable practical applicability. This work provides a feasible molecular design strategy and a reliable anthraquinone-hydrazone scaffold for the development of high-performance chemosensors toward environmental heavy metal ion monitoring.