An Au–Ag@Au fiber surface plasmon resonance sensor for highly sensitive detection of fluoroquinolone residues

Antibiotic residue detection plays an important role in protecting human health, but real-time, rapid, and highly sensitive detection is still challenging. Herein, gold and silver nanoparticles (Au-Ag NPs) were <i>in situ</i> grown on the surface of optical fibers and a 50 nm thick gold film was deposited on the sensor's surface to fabricate the Au-Ag@Au fiber SPR sensor. The sensitivity of the sensor reached 3512 nm per RIU in the refractive index range of 1.328-1.371. When analyzing antibiotic residues in food, the detection limits for Enro and Cip were 0.97 ng mL^-1 and 0.70 ng mL^-1, respectively. Their recoveries ranged from 96.64 to 115.32% and 96.18 to 121.06% in milk samples. There is a high level of antibiotic residues in meat, milk, and aquatic products and this study has significant potential in food safety testing applications. Moreover, this study will be widely used in environmental monitoring (such as heavy metal ions), medical diagnosis (viruses), marine exploration, drug screening and other analytical fields as well.