Silver nanoparticle enhanced fluorescence of europium (III) for detection of tetracycline in milk

Metal-enhanced fluorescence (MEF) has shown a promising potential in fluorometric assays. In this work, the fluorescence of europium (Eu 3+ ) was enhanced by silver nanoparticles (AgNPs) through MEF effect in solution phase, which was applied to the detection of tetracycline (Tc). Tc can coordinate with Eu 3+ modified on the surface of AgNPs to form EuTc complex, which emits strong fluorescence due to an intramolecular energy transfer from Tc to Eu 3+ . The MEF effect of AgNPs further enhanced the emission of EuTc complex; the fluorescence of EuTc on the surface of AgNPs was 4 times higher than that of EuTc in a solution phase. The fluorescence intensity of this probe displayed a good linear response to Tc concentrations in the range of 10   nM to 10   μM with a detection limit of 4   nM, and was applied successfully to determine the levels of Tc in milk with a high selectivity . Compared with other fluorescent detection methods for Tc, the presented method allows simple, direct analysis for Tc without requiring fluorescence enhancement reagents or complicated prepreparation processes. This strategy of AgNP-enhanced fluorescence of lanthanide ions could be applicable to improving homogeneous assays of other molecules.