Latent fingerprint development ability of spinel copper aluminate (CuAl₂O₄) nanoparticles

Fingerprints are still one of the most effective means of forensic detection but degradation during the recovery process leads to a loss of contrast between ridge and background, making them difficult to visualize. In this study spinel copper aluminate (CuAl₂O₄) nanoparticles were synthesized by a facile and cost effective sol-gel method and evaluated for latent fingerprints (LFPs) development on both porous (paper, ceramic, wood) and non-porous (plastic, steel, glass) substrates. Structural characterizations revealed an average crystallite size of 24.5 nm that was found to be smaller than the average particle size of 36.9 nm confirming that the particles consists of nanoscale crystalline domains with some agglomeration. The developed fingerprint exhibited substrate-dependent contrast with normalized contrast ratios increasing from ∼0.30 (paper) to ∼0.60 (glass) under white light and further enhanced to ∼0.74 under UV excitation. UV-assisted visualization enabled improved ridge clarity and facilitated the observation of Level 1 and Level 2 details, with partial enhancement towards finer features. Aging studies demonstrated that identifiable ridge patterns were retained up to 30 days, with improved visibility under UV illumination compared to white light conditions. These findings demonstrate that CuAl₂O₄ nanoparticles provide simple, cost-effective, and reliable approach for fingerprint development, combining surface adhesion and luminescent enhancement for improved forensic applicability.