A dual-emission water-soluble g-C3N4@AuNCs-based fluorescent probe for label-free and sensitive analysis of trace amounts of ferrous (II) and copper (II) ions

In this work, a new dual-emission water soluble graphitic carbon nitride@gold nanoclusters (WS-GCN@AuNCs) nanocomposite is synthesized by a simple method that AuNCs are in-situ grown on the surface of WS-GCN. This composite material emits yellow fluorescence with two emission wavelengths locating at 430 and 520 nm, and of which direct band gap is different from individual WS-GCN. Its fluorescence intensity at 520 nm is quenched rapidly in the presence of ferrous (Fe2+) and copper ions (Cu2+), and relevant fluorescent color changes from yellow to blue, ascribing to the photo-induced electron transfer (PET) mechanism. Furthermore, a reduction strategy of cysteine can be used to distinguish Fe2+ and Cu2+. According to this, a new dual-emission WSGCN@AuNCs-based fluorescent sensor is constructed to detect Fe2+ and Cu2+ with the detection limit of 1.73 and 3.63 nmol L-1, respectively. This proposed method not only exhibits highly selective and sensitive for analysis of Fe2+ and Cu2+ under existence of interfering cations, but possesses excellent performance for detection of trace amounts of Fe2+ and Cu2+ in environmental water.