Europium decorated magnetic nanoparticles design for identification of latent fingerprints on different surfaces applications

The use of multifunctional nanomaterials with magnetic and luminescent properties has gained significant attention in forensic applications for latent fingerprint identification. In this study, we present a synthesis route for preparing chitosan-coated magnetite nanoparticles (MN-CH) by the coprecipitation method and functionalized with europium ions (MN-CH-Eu). These luminescent magnetic nanoparticles hold potential for the identification of latent fingerprints on different surfaces, including metal, plastic, and glass. Remarkably, structural analysis of MN-CH-Eu confirmed the retention of the magnetite crystalline structure through X-ray diffraction. Scanning electron microscopy and EDS mapping provided evidence of europium presence and its homogeneous distribution on the MN-CH surface. The interactions between chitosan and the nanoparticle core were mainly via electrostatic and hydrogen bonding, as confirmed by Fourier-transform infrared spectroscopy. Importantly, the europium-functionalized nanoparticles exhibited characteristic red photoluminescence, dominated by the hypersensitive ⁵D₀ → ⁷F₂ transition (∼612 nm), when excited under UV light. This emission was preserved due to the spatial isolation of Eu³⁺ within the chitosan matrix, which minimized quenching effects from the Fe₃O₄ core. After 24 h at room temperature, developed fingerprints appeared brown under natural light and bright green or reddish under UV illumination, depending on the excitation wavelength (notably 254 nm and 324 nm). The MN-CH-Eu nanoparticles were particularly effective on metal surfaces under both lighting conditions. These findings highlight the successful integration of luminescent and magnetic functionalities within a single nanomaterial, enhancing latent fingerprint detection through both physical adherence and optical contrast, and broadening the scope for forensic applications across various substrates and environmental conditions.