Bilayer systems based on conjugated polymers for fluorescence development of latent fingerprints on stainless steel

Abstract

Fingerprints are a key role in criminal investigations and are the most commonly used form of physical evidence for identifying criminals or to establish a connection between crime scenes. However, visualizing latent (hidden) fingerprints is steal a great challenge, mainly when they are present on metallic surfaces. In this work, a new concept based on the electrodeposition of bilayer systems based on conjugated and fluorescent polymers was used for the development of latent fingerprints on stainless steel. The first layer of Polypyrrole or PEDOY was electrodeposited onto the surface containing a latent fingerprint by oxidation of the monomer in LiClO4 aqueous solution. The second layer of a fluorescent Poly(2,2′:5′,2″-terthiophene) was electrodeposited onto the first layer by using a solution of (C4H9)4NBF4/CH3CN. Such bilayer systems showed fluorescent properties and may be applied in forensic biometry for development of latent fingerprints on stainless steel, since this strategy affords images with high definition in both visible and UV light, permitting the recognition of the ridge patterns and singular points in order to be used for confrontation with other dactyloscopy images.