Rapid Visualization of Latent Fingerprints with Color‐Tunable Solid Fluorescent Carbon Dots

Abstract Latent fingerprints (LFPs) imaging is the most important approach to identify individuals, and there is a persisting need for the development of simple, rapid, accurate, and universal LFPs recognition methods. The nitrogen‐ and sulfur‐doped solid fluorescent carbon dots (N,S‐SFCD) are synthesized with a simple microwave‐assisted method by using l‐glutathione and citric acid as precursors. The obtained N,S‐SFCD has a uniform size from 2 to 7 nm with quantum yield over 48%. The presence of heteroatoms and functional groups on the surface endows the N,S‐SFCD with good dispersibility and strong fluorescence emission, and overcomes the typical aggregation‐induced fluorescence quenching, thus allowing the N,S‐SFCD to be used in both solution and their powder forms. Furthermore, the color‐tunable fluorescence, electrostatic interaction with fingerprints, and good stability enable N, S‐SFCD to act as an excellent chemosensor for fluorescence imaging. LFPs are detected with high resolution through powder method, and their second‐ and third‐level substructures are clearly identified. The method is validated for LFPs visualization on various substrates, and aged (7, 15, and 30 d) LFPs can also be successfully stained with N,S‐SFCD. The results demonstrate that the N,S‐SFCD as a developer has great potential in LFPs imaging for forensic investigations.