Development of a rapid and simple tetracycline detection system based on metal-enhanced fluorescence by europium-doped AgNP@SiO core-shell nanoparticles.

We herein describe a rapid and selective sensing platform for tetracycline (Tc), which relies on the metal-enhanced fluorescence (MEF) effect of europium (Eu)-doped silver-silica core-shell nanoparticles (AgNP@SiO). The developed assay utilizes AgNP@SiO as a key detection component, which is systematically optimized to have a silica shell thickness suitable for the effective MEF phenomenon. In principle, the AgNP@SiO, which binds to Eu through the electrostatic interaction, captures Tc by selective chelation with Eu, leading to significant fluorescence enhancement of the EuTc complex. Based on this novel strategy, we determined Tc as low as 83.1 nM with a total assay time of less than 10 min, which is comparable to or better than that of the previous fluorescence-based methods. Furthermore, the practical applicability of this strategy was successfully demonstrated by detecting Tc in tap water. This work highlights the unique features of AgNP@SiO for MEF-based biosensing applications.