ZrO ₂ -decorated Pluronic F-127-modified gCN nanosheets for the IFE-driven detection of tetracycline

The widespread use of broad-spectrum antibiotics such as tetracycline (TC) and oxytetracycline hydrochloride (OTC) in livestock and agricultural sectors has accelerated the emergence of antibiotic-resistant bacteria and contributed to environmental contamination, posing serious threats to ecosystems and public health. To address these concerns, a fluorometric sensing platform based on zirconium dioxide nanoparticles anchored onto Pluronic F-127-modified graphitic carbon nitride sheets (ZrO₂/P-gCN) was developed for the rapid and sensitive detection of TC and OTC. The incorporation of ZrO₂ nanoparticles introduced abundant active sites and enhanced electron transfer, while Pluronic F-127 improved the aqueous dispersibility and uniformity of gCN sheets. The resulting ZrO₂/P-gCN nanocomposite exhibited an intense blue fluorescence at 450 nm under a 370 nm excitation, which was markedly quenched in the presence of antibiotics. The quenching behavior followed the Stern-Volmer relationship, yielding K_SV values of 1.18 × 10⁵ M^-1 for TC and 1.32 × 10⁴ M^-1 for OTC, with detection limits as low as 0.421 µM and 0.420 µM, respectively. The quenching rate constants surpassed the diffusion limit, confirming that the inner filter effect (IFE) and static quenching were the main mechanisms. This sensor showed high selectivities for TC and OTC even in the presence of common interferents and achieved 93%-105% recovery in environmental water samples. The combination of ZrO₂ nanoparticles and Pluronic-modified gCN sheets provides a simple, affordable, and eco-friendly sensor for the real-time detection of antibiotic residues in water.