Color-Tunable Binuclear (Eu, Tb) Nanocomposite Powder for the Enhanced Development of Latent Fingerprints Based on Electrostatic Interactions

Fluorescence color of rare earth-based nanopowder can be modulated by regulating the molar ratio of components, which offers a promising strategy in many fields of applications. Herein, a series of binuclear EuxTb1–x(AA)3Phen (x = 1, 0.75, 0.5, 0.25, 0.1, 0) complexes were fabricated using acrylic acid (AA) as the first ligand and using 1,10-phenanthroline (Phen) as the second ligand. The characterization results showed that this novel binuclear (Eu, Tb) complex can emit strong red or green light via simply varying the molar ratio of europium and terbium. Moreover, the results of spectroscopic and zeta potential analyses suggested that there was an electrostatic adherence mode in the interaction between the EuxTb1–x(AA)3Phen complex and fingerprint residues. Importantly, our EuxTb1–x(AA)3Phen nanopowder was successfully applied to the enhanced development of latent fingerprints on various surfaces by the powder dusting method, exhibiting a high contrast, sensitivity, and selectivity, as well as a low detection limit in forensic science, which was further confirmed by analysis with an automatic fingerprint identification system. In summary, our synthetic rare earth-based nanopowder exhibits promise as an ideal fluorescent probe for the enhanced development of latent fingerprints, based not only on physical absorption at the macrolevel but also on electrostatic interactions between our rare earth complex and fingerprint residues at the molecular level, which could provide an enhanced affinity compared with traditional fingerprint powders.