Controllable excitation-dependent fluorescence triggered by the increasing graphitic nitrogen in carbon dots and its application in multi-analyte detection

Carbon dots ( CD s) with controllable excitation-dependent fluorescence ( EDFL ) were elaborately prepared for the application of multiplex metal ion discrimination. A serial of CD samples were synthesized through a simple solvothermal reaction in which extra nitrogen sources with enhancing chemical reducibility were added into a specific nitrogen-contained precursor. Both experimental characterizations and theoretical calculations based on density functional theory have proved that the functional group of graphitic nitrogen ( GN ) is the key factor to achieve EDFL , and the content of GN was determined by the reducibility strength of extra nitrogen sources in the synthesis. In that case, sensing channels with different response behaviours to multiplex analytes can be formed due to the controllable EDFL of CD s. As a result, seventeen types of metal ions can be detected and recognized through the as-prepared CD probes. This work provides a novel angle to understand and engineer the EDFL property of CD s, as well as a facile strategy to appropriately construct high effective sensing channels for multi-analyte detection.