Robust Serum Albumin-Responsive AIEgen Enables Latent Bloodstain Visualization in High Resolution and Reliability for Crime Scene Investigation

Bloodstains provide admissible information for crime scene investigators. The ability to resolve latent bloodstains that are commonly found in real scenarios is therefore pivotal to public security. Here we report a facile approach for invisi-ble bloodstain visualization based on the Click reaction between serum albumin and TPE-MI, an aggregation-induced emission luminogen (AIEgen). Compared to the widely adopted methods based on the harsh catalytic oxidation activity of hemoglobin, this working principle benefits from the specificity of the mild catalyst-free thiol-ene Click reaction that improves the reliability and resolution. In addition, the mild conditions preserve DNA information and bloodstain patterns, and the excellent photophysical properties of the AIEgen afford high sensitivity and stability (> 1yr). Such excellent performance cannot be achieved by conventional AIEgens and aggregation-caused quenching luminogens with similar struc-tures. The TPE-MI outperforms the benchmark luminol-based technique in visualizing latent bloodstains as showcased in two mock crime scenes: spattered blood track and transfer blood fingerprint. The disclosed method is an advancement in forensic science that could inspire future development of technology for bloodstain visualization.