Polyethyleneimine mediated interaction for highly sensitive, magnetically assisted detection of tetracycline hydrochloride

Antibiotic residues in food have become the focus of attention. In this work, we report a simple self-assembly method to fabricate magnetic Fe 3 O 4 @ [email protected] complex substrate for surface enhanced Raman scattering (SERS) detection of tetracycline hydrochloride (TC), a widely used antibiotics in breeding industry. Assembled Ag nanoparticles (AgNPs) on Fe 3 O 4 NPs helps form more SERS hotspots by magnetic induction, which facilitate the direct aqueous detection and high sensitivity (EF = 4.0 × 10 6 in wet state) of the Fe 3 O 4 @ [email protected] sensor. Polyethyleneimine (PEI) not only acts as interlayer for AgNPs assembly on Fe 3 O 4 particles, but can also direct the interaction between TC and SERS substrate. The binding ratio between B, C, D rings of TC and PEI is calculated to be 1:4 by Ultraviolet–visible spectroscopy (UV–vis) characterization. Simulation study also confirms the multiple TC-PEI interaction mode (hydrogen, σ-π, cation-π). Fe 3 O 4 @ [email protected] sensor also shows very high stability (signal decreases < 5% after 93 days). Fe 3 O 4 @ [email protected] SERS sensing array could have a great potential for real-time sensitive detection of analytes. More importantly, this rational adjustment of interaction sites between substrate and analyte is expected to be a new strategy for the improvement of SERS detection sensitivity and selectivity.