Self-assembled copper nanoclusters structure-dependent fluorescent enhancement for sensitive determination of tetracyclines by the restriction intramolecular motion

The exploration of turn-on fluorescent method for sensitive detection of tetracycline is still challenging. This paper reports a kind of specific structure of self-assembled copper nanoclusters (CuNCs), greatly enhancing the fluorescence emission intensity of tetracycline (TC). Fluorescence enhancement is mainly ascribed to that tetracycline can defuse into the compatible space of special structure of self-assembled CuNCs, and intramolecular motion of TC can be effectively restricted, leading to fluorescence emission enhancement of TC. The assay enables TC to be detected with high sensitivity and linear response that covers the 200 nM to 50 μM TC concentration range with a 40 nM limit of detection, which is lower by 50-fold than the method without self-assembled CuNCs. Furthermore, the strategy is further applied for determining TC contents in milk and urine samples. A novel fluorescent strategy has been developed for the sensitive detection of tetracycline based on the specific structure of self-assembled CuNCs and the restriction intramolecular motion. [Display omitted] •A novel strategy has been exploited for the improvement of the fluorescence signal of tetracyclines through RIM.•The special structure of self-assembled CuNCs can offer a more beneficial microenvironment for fluorescence enhancing.•The LOD for TC assay was lower by 50-fold than the method without 4CH3-CuNCs.•The method was simple and cost-effective, and performed within several minutes at room temperature.•This strategy was free of any fluorescence dye label and other complex design.