One-step synthesis of a dual-emitting carbon dot-based ratiometric fluorescent probe for the visual assay of Pb2+ and PPi and development of a paper sensor

Herein, an easy and effective ratiometric fluorescent nanoprobe for the selective detection of Pb2+ and pyrophosphate (PPi) was developed based on label-free carbon dots (CDs). The CDs showed dual emission bands at 477 and 651 nm under a single-wavelength excitation (391 nm). Pb2+ and PPi were sequentially detected by the sensor with high reliability and accuracy via the exploitation of the fluorescence intensity ratio (F-477/F-651). The dual emission sensor exhibited high selectivity and excellent sensitivity for Pb2+ and PPi than for other analytes with detection limits as low as 0.055 mu M and 0.089 mu M, respectively. Moreover, the fluorescent CDs changed from pink to cyan and from cyan to pink and could be used as a fluorescent paper sensor for the visual detection of Pb2+ and PPi. To the best of our knowledge, this is the first report on the ratiometric fluorescence detection of Pb2+ and PPi by CDs; therefore, the as-synthesized CDs show great potential for application in the determination of Pb2+ and PPi in real samples.