Reaction Temperature-Controlled synthesis of multicolor aggregation-induced emission carbon dots and their various applications in anti-counterfeiting, fingerprint detection

Although carbon dots (CDs) are a fluorescent nanomaterial with tremendous development potential, solid-state CDs have not been effectively explored due to the fluorescence quenching effect caused by aggregation. Herein, multi-color tunable aggregation-induced emission (AIE) CDs were constructed using dithiosalicylic acid (DTSA) and ammonium sulfate as raw materials by controlling the reaction temperature. Herein, the AIE behavior of CDs is mainly ascribed to the presence of disulfide bonds, which not only enhance the hydrophobicity of CDs, but also restrict the intramolecular rotation of the aggregated CDs, thus improving the surface state fluorescence of CDs, resulting in solid-state fluorescence (SSF) in longwave emission. More importantly, the emission behavior of the obtained CDs can be regulated by controlling the reaction temperature, which may be due to the synergistic effect caused by the differences in N, S content, functional group ratio, and size distribution of synthesized CDs at different temperatures, meanwhile producing different AIE behavior and fluorescence resonance energy transfer (FRET) efficiency, leading to the corresponding five different colors of AIE CDs. Furthermore, the synthesized AIE CDs have been successfully employed in various applications, including discoloration hydrogel, color-changing anti-counterfeit paper, and efficient latent fingerprints detection with enhanced details.