Detection of several quinolone antibiotic residues in water based on Ag-TiO₂ SERS strategy

Herein, a surface-enhanced Raman scattering (SERS) strategy based on semiconducting substrate was exploited for detection of several antibiotic residues both in ultrapure water system and in actual water system. The as-prepared Ag-TiO₂ (Ag synchronously deposited and doped TiO₂) nanoparticle SERS-active substrate can achieve high sensitive SERS detection for difloxacin hydrochloride, ciprofloxacin, enrofloxacin, danofloxacin and enoxacin (five widely used quinolone antibiotics) in actual water samples, and the detection limits are as low as 4.36 × 10^-12, 7.08 × 10^-11, 3.94 × 10^-11, 3.16 × 10^-11 and 3.15 × 10^-10 mol/L, respectively. These detection limits are far below the maximum of residue limit (3.01 × 10^-7 mol/L) stipulated by the European Union. And, the desirable quantitative relationships can be obtained in a wide concentration range. The recoveries of five antibiotic residues from spiked actual water samples are found to be more than 80.8% with the relative standard deviations between 2.1% and 4.7%. Even, the proposed SERS method can accurately distinguish every antibiotic species from a mixed antibiotic residue sample with multiple antibiotics. And, Ag-TiO₂ nanoparticles can also serve as an efficient photocatalyst for photocatalytic degradation of these antibiotic residues, which provides a multi-functional platform for synchronous determination and degradation of antibiotic residues in real environment.