Revelação de impressão digital latente em superfície metálica a partir da eletrodeposição de polímeros conjugados

Abstract

Fingerprint analysis is one of the most reliable methods of personal identification. In forensic area it can be used to place a suspect in a crime scene. In most cases, the collected fingerprints are latents, that is, they are not visible and need to be revealed. There are many techniques in order to reveal a latent fingerprint, such as powder technique, iodine vapour, ninhydrine, ethyl cyanoacrylate, among others. However, these techniques present limitations when applied in metallic surfaces, such as the need for recent sample collection or even though the use of some toxic reagents for their reveal. This work exploited the use of conjugated polymers to reveal latent fingerprints in metallic surfaces. It was used pyrrole and 3,4-ethylenedioxythiophene as monomers, and the polymerization occurred onto the metallic surface in which the latent fingerprint was present. The fingerprint revelation is a result of the contrast between the metallic surface and the lines present in the fingerprint surface where there was polymer deposition due to the presence of sebaceous sweat in the surface that acts as an isolating mask. In order to classify the revealed fingerprints, it was used the theory developed by Edmord Locard, who stablished the 12 points rule. The fingerprints revealed in this work had at least 44 determining points. Besides the revealed points, it was clearly observed the nuclear region, the presence of sweat pores, interpapillary grooves and the papillary ridges present in the revealed fingerprint. Aiming to make this process more accessible, it was used organic dyes as polypyrrole dopant agents, such indigo carmine, methyl red and methyl orange. The fingerprints revealed using the organic dye methyl red were those that presented better contrast between the fingerprint and the metallic surface.