Trace detection of ciprofloxacin antibiotic using surface-enhanced Raman scattering coupled with silver nanostars

In recent years, the abuse of antibiotics in livestock and aquaculture has become a global concern, so the detection of antibiotic residues in food is a topic of growing interest. At present the surface-enhanced Raman scattering (SERS) technique is promising as a useful tool in trace detection of chemical substances including antibiotics. In this report, we present the trace detection of cip-rofloxacin - a widely used antibiotic by recording its SERS spectrum, using a SERS substrate made of silver nanostars (AgNSs) coated on an aluminum foil. In turn, AgNSs are colloidal star-shaped silver nanoparticles that have been very simply synthesized by a two-step chemical reduction of silver nitrate in an aqueous solution at room temperature with hydroxylamine followed by tri-sodium citrate. The synthesized AgNSs have a total size of 250-300 nm with many pointed arms of 60-80 nm length protruding from the central core. It was found that with a SERS substrate assembled from the above AgNSs coated on an aluminum foil, due to the synergistic effect be-tween AgNSs and aluminum foil, the Raman enhancement factor of the SERS substrate was increased significantly. As a result, a SERS substrate with a Raman enhancement factor as high as 4 x 109 was created and ciprofloxacin was detected to very low concentrations, with a detection limit of 0.23 ppb.