Multi‐Emissive Solid State Carbon Dots Modified With Ligands for Recognition of Latent Fingerprints

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Solid‐state fluorescent materials with tunable visible emission are highly desirable for high‐contrast latent fingerprint (LFP) visualization; however, most carbon dots (CDs) undergo aggregation‐caused quenching in the solid state. In this study, we present a ligand‐directed approach to engineer aggregation‐induced emission (AIE)‐active CD powders with tunable solid‐state fluorescence (SSF) for forensic applications. The hydrothermally synthesized nitrogen‐doped humic acid‐derived carbon dots (N‐hCDs) were functionalized with two aromatic aldehydic ligands via Schiff‐base chemistry, producing CDs@I and CDs@D that display distinct light‐red and yellow solid‐state emission. The emission tuning arises from ligand‐induced modulation of surface states, restricted intramolecular motion, and ordered lamellar self‐assembly, which together suppress nonradiative decay in the aggregated state. The SSF powders enable high‐contrast visualization of LFPs on diverse nonporous substrates, resolving level‐2 and level‐3 ridge features under UV illumination. Moreover, the materials exhibit excellent thermal stability, photostability, and aging resistance, underscoring their robustness for practical forensic applications. This work demonstrates a versatile surface‐engineering strategy for color‐tunable solid‐state emissive CDs, broadening their utility in LFPs detection.