Development of AIEgen–montmorillonite nanocomposite powders for computer-assisted visualization of latent fingermarks†
The forensic analysis of fingerprints is widely used to identify criminals and has become the basis of court evidence. In the work described in this paper, a new composite was developed for latent fingerprint (LFP) imaging; this composite was made by combining the aggregation-induced emission luminogen (AIEgen) salicylaldehyde azine (SAA) with montmorillonite (MMT). Gray value analysis and pattern recognition analysis based on MATLAB were conducted to evaluate the quality of the obtained LFP in comparison with the reference fingerprint obtained using Finger Reader. Due to the bright yellow solid-state emission of SAA and high absorptive capacity of MMT, details of fingermarks such as grooves and ridges were obtained at high resolution. We also obtained fluorescent fingerprint images in which second-level particulars were visualized with high quality, crucial for being able to carry out reliable personal identification. Besides, the composite was applied for LFPs on virtually all types of smooth substrates with high sensitivity and high efficiency. Compared with commercial fingerprint powder, AIEgen-based composites showed a higher degree of matching with reference fingerprints. In addition to SAA, two other AIEgens were also applied for LFP imaging and showed high resolution. The results showed that the AIEgens can serve as an alternative fluorescent material to commercial fluorescent materials used for LFP imaging.