Dumbbell-shaped carbon quantum dots/AuNCs nanohybrid as an efficient ratiometric fluorescent probe for sensing cadmium (II) ions and L-ascorbic acid

In this work, for the first time, an efficient carbon quantum dots/gold nanoclusters (CQDs/AuNCs) nanohybrid based ratiometric fluorescent probe for sensitive and selective sensing of cadmium (II) ions and L-ascorbic acid (AA) has been established. The blue emissive CQDs, prepared by a one-step hydrothermal treatment with alanine and histidine, play the role of reference fluorophore. The red emissive AuNCs, capped by 11-mercaptoundecanoic acid (MUA), serve as a specific recognition element. Different from MUA-capped AuNCs, the proposed CQDs/AuNCs nanohybrid exhibits high selectivity and sensitivity to cadmium (II) ions with a detection limit of 32.5 nM, which is attributed to the static quenching and the inner filter effect (IFE) of Cd2+ to CQDs/AuNCs nanohybrid. Unbelievable, in the presence of AA, the above-quenched sensor is recovered gradually. The proposed fluorescence sensor displays an enhanced performance for AA determination in the range from 0.15 to 15 mu M (R = 0.995) with a detection limit down to 0.105 mu M. More importantly, this fluorescent "on-off-on" method also offers the excellent performance to Cd2+ and AA detection in lake water and in human serum, respectively. (C) 2015 Elsevier Ltd. All rights reserved.