Metal-Organic frameworks encapsulated Ag Nanoparticle-Nanoclusters with enhanced luminescence for simultaneous detection and removal of Chromium(VI)

Metal nanoclusters (NCs) have emerged as a class of promising luminescent materials for sensing, but the low luminescence efficiency hindered their applications. In this work, highly luminescent composites were synthesized by encapsulating D-penicillamine (DPA) capped silver nanoparticle-nanoclusters (AgNP-NCs) into zeolitic imidazolate frameworks (ZIF-8) (denoted as AgNP-NCs@ZIF-8) and were applied for simultaneous detection and removal of chromium(Ⅵ). The photoluminescence intensity of the AgNP-NCs was enhanced by (66 ± 5) folds due to the confinement of ZIF-8 shell, and the lifetime was prolonged from (50.9 ± 1.8) ns to (15.9 ± 0.4) μs. More importantly, thanks to the strong luminescent property of AgNP-NCs and porous structure of the ZIF-8 shell, the AgNP-NCs@ZIF-8 composites not only allowed for the detection of Cr(Ⅵ) as luminescent probe but also exhibited good adsorption capacity of Cr(Ⅵ). The luminescence intensity decreased linearly with Cr(Ⅵ) concentration in the range of 40 to 400 μM, and the limit of detection was determined to be (23.5 ± 0.8) μM. They also exhibited high selectivity toward total chromium in various interfering metal ions and good performance in real water samples. These results indicated that AgNP-NCs@ZIF-8 could serve as an attractive candidate for simultaneous detection and removal of Cr(Ⅵ) in environmental monitoring and protection.