Eco-friendly self-cleaning magnetic MIPs-SERS sensor for ultra-sensitive detection of ciprofloxacin in complex water environments

Because of its broad antibacterial range, the fluoroquinolone antibiotic ciprofloxacin (CIP) has been used extensively to treat bacterial infections in humans. However, it has been demonstrated that the excessive use of CIP will endanger human health and destroy the ecological environment. Therefore, rapid, facile and accurate detection of CIP is essential for real-world applications. In this study, a novel surface-enhanced Raman scattering (SERS) sensor with self-cleaning ability was synthesized and successfully employed for ultra-sensitive and specific detection of CIP. Specifically, ZnFe 2 O 4 @SiO 2 -Au (ZSAu) nanocomposites (NCs) with different Au nanocrystals gap were developed. The relationship between various Au nanocrystals gap and SERS performance was investigated using finite-difference time-domain (FDTD) method. The solid-state Raman scattering spectrum of CIP molecule was also optimized and calculated using the density functional theory (DFT) method. After modifying with molecularly imprinted polymers (MIPs), ZSAu-MIPs NCs achieved specific detection of CIP in water environments, with the detection limit of low as 10 −9 M for CIP. A strong linear correlation between SERS intensity and the logarithm of CIP concentration suggested that ZSAu-MIPs NCs could be applied for quantitative detection of CIP at uncertain concentrations. In addition, ZSAu-MIPs NCs with self-cleaning ability could be recycled and reused with the assistance of magnet. After six cycles, ZSAu-MIPs NCs still exhibited good SERS performance. This magnetic MIPs-based SERS sensor offers a promising and recyclable method for ultra-sensitive detection of CIP in complex water environments.