Simple synthesis of carbon dots/organosilicon composites with tunable solid-state emission and size for accurate latent fingerprint identification

Carbon dots (CDs) have desirable prospects for replacing conventional fluorescent materials in the field of fingerprint powder due to their attractive fluorescence, environmental friendliness, and stability. Designing solid-state fluorescent CD-based composites with suitable sizes for accurate latent fingerprint identification is still a huge challenge. Herein, CDs embedded in organosilicon (CDs-OSi) composites were synthesized by utilizing the reaction between 3-ureidopropyl triethoxy silane and L-(-)-malic acid. The obtained CDs-OSi composites display tunable fluorescence from blue to green just by controlling the volume ratio of H2O and ethanol in a solvothermal process. In particular, CDs-OSi composites simultaneously exhibit a controllable and uniform size from 0.12 mu m to 5 mu m. The CDs-OSi composites with different emissions and sizes were further applied to detect latent fingerprints (LFPs). The results show that CDs-OSi composites can be easily adsorbed onto the grease of the fingerprint, and level 2 and level 3 characteristics can be clearly identified by a simple powder dusting method. Furthermore, CDs-OSi composites are validated for the collection and identification of LFPs on different substrates. The results prove that CDs-OSi composites have great development prospects as developers in LFP visualization for forensic investigations. The CDs-OSi composites with tunable emission and size were prepared by adjusting the volume ratio of H2O and EtOH in solvothermal. The CDs-OSi composites were applied in identification of latent fingerprint with effective definition and contrast.