Preparation of fluorescent conjugated polymer micelles with multi-color emission for latent fingerprint imaging

Abstract

The development of novel imaging agents for fluorescence detection of latent fingerprint is still important for criminal investigation and identity recognition. Herein, we reported a simple and robust method to prepare multi-color conjugated polymer micelles for visualization of fingerprints. A conjugated polyelectrolyte, poly[(9,9-bis(3′-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN), was dissolved in water forming polymer micelles with blue emission. Green and red emissions were facilely achieved by incorporating small organic fluorophores including coumarin 6 (C6) and Nile red (NR) into the PFN micelles, respectively. These micelles exhibited bright fluorescence both in solution and solid film, where significant aggregation-caused quenching was avoided and fluorescence resonance energy transfer from PFN to C6 or NR was enhanced. Through a simple solution method, these polymer micelles proved their high affinity towards the fingerprint ridges. Accordingly, fluorescent fingerprint images with high-resolution were obtained, which were less interfered by fluorescence background from substrate and overlap between adjacent fingerprints.