A Green Synthesised B/nZVCu-M On-Off Fluorescence Sensor for Dopamine Detection and its Reusability.

The real-time and selective detection of dopamine (DA) in complex biological systems remains a critical challenge due to its low physiological concentrations and interference from structurally similar biomolecules such as ascorbic acid and uric acid. Traditional analytical techniques often fall short in terms of specificity, cost-effectiveness, and ease of deployment in biological matrices. To address this gap, we developed a highly selective fluorescent nanosensor based on bentonite-supported Cu-based bimetallic nanoparticles (B/nZVCu-Ni/Ag), synthesized via a green route using Lawsonia inermis extract. The phytogenic synthesis facilitated the reduction and stabilization of the nanoparticles, yielding well-dispersed crystalline domains (10-13 nm) anchored uniformly on the bentonite layered sheets. Comprehensive characterization through PXRD, FTIR, TEM, UV-Vis, and fluorescence spectroscopy confirmed the formation and functional integration of the nanoparticles. Among the two variants, the B/nZVCu-Ni (D1) probe exhibited superior fluorescence enhancement upon interaction with DA, achieving a detection limit as low as 5.13 nM and a high binding constant (K = 1.47 × 10⁵ M⁻¹). The sensor demonstrated excellent selectivity, with negligible response to common interfering agents, and displayed a robust reversible on-off fluorescence behavior upon sequential addition and removal of DA using EDTA , confirming dynamic binding reversibility. These results establish the B/nZVCu-M nanoprobes, particularly D1, as promising candidates for ultrasensitive, interference-resistant, and reusable fluorescence-based detection of dopamine in synthetic urine sample.