Ratiometric visual detection of tetracycline residues in milk by framework-enhanced fluorescence of gold and copper nanoclusters.

We reported a novel dual-emission fluorescence probe fabricated by encapsulating both gold (AuNCs) and copper nanoclusters (CuNCs) into zeolitic imidazolate framework-8 (ZIF-8). Obtained composite (AuCuNCs@MOF) was utilized for ratiometric determination of Tetracycline (Tcy) antibiotic. Under excitation at 400 nm, the AuCuNCs@MOF composite displayed two emission peaks at 520 and 650 nm which were originated from AuNCs and CuNCs, respectively. Upon the addition of Tcy, the red emission intensity of the nanoparticles at 615 nm was significantly decreased, while the green emission at 520 nm stayed almost constant which resulted in a clear fluorescence color change from red to green under a UV lamp. The logarithm of the fluorescence ratio against the concentration of Tcy exhibited a satisfactory linear relationship from 20 to 650 nM with a detection limit (LOD) of 4.8 nM. Current probe was applied for Tcy quantification in milk samples with superior results.