Aggregation/assembly induced emission based on silk fibroin-templated fluorescent copper nanoclusters for “turn-on” detection of S2−

Herein, we observed that the simple one-pot green method synthesized fluorescent silk fibroin (SF) protected copper nanoclusters (CuNCs) possessing unique aggregation/assembly induced emission enhance (AIEE) characteristics with the assistance of sulfide ion in aqueous solution. The interaction of CuNCs with S2− was further investigated by fluorescence spectroscopy, UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. It demonstrated that the S2− can induced the ultrasmall Cu nanoclusters of ca. 2.8 nm orderly assembled to large nanoparticles of uniform rod-like with the size (47 ± 2) × (15 ± 2) nm by transmission electron microscopy (TEM). And the fluorescence intensity of the dispersed CuNCs was increased with the increase of absolute quantum yield from 1.6% to 4.9%. More importantly, the assembly large Cu nanoparticles are also monodispersed in size and morphology, which provides a distinctive advantage for analytical applications. Based on this, SF@CuNCs can be developed into a practical nanosensor for “turn-on” luminescence detection for S2− with a highly sensitive and selectivity. The linear response with the S2− concentrations range from 5.0 μM to 110.0 μM and detection limit was 0.286 μM. We demonstrated this assembled nanostructure as a powerful analytical platform for S2− detection.