Cross-Linking Induced Emission of Polymer Micelles for High-Contrast Visualization Level 3 Details of Latent Fingerprints

Rationally developing an intelligent tool for high-contrast fluorescence imaging of latent fingerprints (LFPs) is gaining much concern in many applications such as medical diagnostics and forensic investigations. Herein, the off–on fluorescent polymer micelles (PMs) have been rationally designed and synthesized for high-contrast fluorescence imaging of LFPs through the cross-linking reaction of hydrazine (N2H4) and aldehyde group of polymer. Excitingly, the cross-linking (N2H4) induced emission of PMs has the property of aggregation-induced emission (AIE) and excited state intramolecular proton transfer (ESIPT), which could effectively address the notorious aggregation-caused quenching (ACQ) effects of conventional organic dyes. In addition, the cross-linking strategy can not only improve structural stability of PMs but also enhance its fluorescence brightness. The experiment results demonstrated that PMs showed high water dispersibility (100% aqueous solution), high selectivity, large Stokes shift (∼150 nm), good photostability, and excellent long-term stability. Because of the hydrophobic interaction between the PMs and fingerprint components, the PMs preferentially adhered onto the ridges of fingerprint, and then cross-linking (N2H4) induced emission properties endowed the PMs for high-contrast imaging of LFPs in different substrates, especially the levels 1–3 details of LFPs. We expect that this strategy will provide vital support for LFPs technology.