Revelação de impressões digitais latentes usando nanopartículas fluorescentes baseadas em sílica mesoporosa modificada com quitosana

Abstract

Recently, it has been reported that hydrophobicity and lipophilicity are important parameters for the mechanism of fingerprint detection, as lipids are their main organic component. In this context, the functionalization of nanomaterials with hydrophobic molecules or functional groups has become an important tool for developing new detection agents with enhanced sensitivity. However, most research tends to overlook the extent to which this factor influences the quality of the detection. Mesoporous silica nanoparticles of the MCM-41 type, due to their excellent properties, such as high surface area and biocompatibility, have been widely investigated in biomedical applications and, more recently, in forensic applications. In this work, MCM-41 nanoparticles were synthesized by the sol-gel method and functionalized with auramine O (MCM-41@AO) and with chitosan and auramine O (MCM-41@Qui@AO). Chitosan was used to endow the nanoparticles with high lipophilicity. These nanoparticles were used as powder developers for the detection of latent fingerprints under various conditions (different substrates and donors, aged fingerprints, and minimal residue concentrations) to compare the influence of chitosan modification on the quality of the detection. Both formulations were characterized by FT-IR, TEM, BET, UV-Vis, and fluorescence spectroscopy. The biopolymer chitosan and the fluorophore auramine O were successfully incorporated into the mesoporous silica matrix through a non-covalent method, and the so-called MCM41@AO and MCM-41@Qui@AO exhibited approximate sizes of 100 nm, spherical morphology, and ordered, well-defined hexagonal pore arrangements. Surface area analysis (BET) confirmed that chitosan was incorporated both on the external surface and within the internal pores of MCM-41, and photophysical tests demonstrated that both nanoparticles possess good luminescent properties. Application tests of these materials in latent fingerprint detection showed a significant improvement in the quality of the revealed images using chitosan-modified fluorescent nanoparticles, which exhibited high brightness, contrast, and clarity of the fingerprint ridges compared to those where no surface modification was performed. MCM-41@Qui@AO nanoparticles demonstrated high efficiency and consistency even in the detection of fingerprints aged up to 60 days and with minimal residue concentrations, as evidenced by fingerprint depletion tests. Using the UK Home Office classification scale, an average of 97.78% of the revelations using this material, under the various conditions addressed in this study, were rated 3 – 4 and classified as identifiable, compared to 73.34% of ratings 3 – 4 obtained for revelations with MCM-41@AO. This significant increase in efficiency and sensitivity of MCM41@Qui@AO corroborates previous studies indicating that the lipophilic nature of new materials is a determining factor for their effective application in the detection of latent fingerprints.