Self-cleaning and recyclable magnetic MIP-SERS sensor based on ZnFe2O4-Cu2O-Au@Ag nanocomposites for ultrasensitive and selective detection of ciprofloxacin

Ciprofloxacin (CIP) is widely utilized for the treatment of bacterial infections due to its broad-spectrum antibacterial properties; however, excessive residues inevitably cause environmental pollution. Therefore, the development of sensitive and accurate analytical methods for CIP detection remains important. Herein, a novel self-cleaning surface-enhanced Raman scattering (SERS) sensor was fabricated for the ultrasensitive and specific detection of CIP. ZnFe 2 O 4 -Cu 2 O-Au@Ag (ZCAA) nanocomposites (NCs) were synthesized by decorating ZnFe 2 O 4 -Cu 2 O with various amounts of Au@Ag nanocrystals, thereby integrating dual functions of pollutant detection and photocatalytic degradation. Finite-difference time-domain (FDTD) simulation was adopted to elucidate the correlation between Au@Ag loading density and SERS performance. After modification with molecular imprinted polymers (MIPs), the prepared ZnFe 2 O 4 -Cu 2 O-Au@Ag-MIPs (ZCAA-MIPs) exhibited robust anti-interference capability, enabling specific detection of CIP even in the presence of structurally similar antibiotics such as tetracycline (TC) and oxytetracycline (OTC). A limit of detection (LOD) of 9.3 × 10 −11  M was achieved in aqueous media. Furthermore, the sensor successfully identified trace CIP on the epidermal surfaces of river snail, demonstrating its practical applicability in real-world samples. Time-resolved photoluminescence (TRPL) and X-ray photoelectron spectroscopy (XPS) analyses revealed that the synergistic interaction between the ZnFe 2 O 4 -Cu 2 O heterojunction and Au@Ag nanocrystals accelerated charge carrier migration and optimized interfacial charge transfer. Density functional theory (DFT) calculations further verified the superior degradation capacity of ZCAA substrate. Benefiting from its intrinsic magnetic properties, ZCAA-MIPs sensor was easily recycled under external magnetic field and retained stable SERS performance after five consecutive recycling cycles. This magnetic MIPs-SERS sensor provides a reliable and sustainable platform for monitoring CIP residues in complex water environments.