Directly reusing waste fish scales for facile, large-scale and green extraction of fluorescent carbon nanoparticles and their application in sensing of ferric ions

Fluorescent nanomaterials have important applications in environmental monitoring and biomedicine and imaging. However, their preparation often is cumbersome, expensive, and extremely small-scale, requires harsh conditions, which limit their wide and practical applications. Herein, by directly reusing waste fish scales with intrinsic fluorescent property as precursors, we developed a facile, large-scale, inexpensive, and green method for extraction of fluorescent carbon nanoparticles for sensing of Fe3+. Our preparation approach only requires soaking fish scales in water without harsh conditions and complicated operations, only based on physical exfoliation, not limited by containers. Fish-scale-derived fluorescent carbon nanoparticles with bright blue fluorescence and a quantum yield of 15.6% are irregular spheres with a diameter of more than 60 nm, contained smaller nanodots with a diameter of about 4.2 nm, which has obvious lattice fringes of 0.23 nm. Elemental and functional group analysis confirmed that fluorescent carbon nanoparticles were mainly composed of C, O, and N, had hydroxyl, amine, and carbonyl groups, and similar in composition to collagens and hydroxyapatites. Fluorescent carbon nanoparticles can be used for fluorescent quenching-based detection of Fe3+ with a linear range of 0-6.25 mu M and detection limit of 0.144 mu M, and have good recoveries for Fe3+ in actual water samples and human serum with low relative standard deviations. This study not only adds a new dimension to provide a large-scale, simple, green, and promising method for reuse of waste fish scales, but also offers a new idea for the large-scale preparation and application of fluorescent carbon nanomaterials.