Matrix-tunable Eu3+/1,10-phenanthroline silica nanomaterials for high-resolution fingerprint development

Abstract

In this study, 1,10-phenanthroline (OP) was employed as an organic sensitizing ligand for Eu³⁺, and three Eu³⁺/OP silica gel fluorescent nanomaterials were prepared via a sol-gel route using tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and phenyltrimethoxysilane (TMPS) as silica matrices. The enhanced fingerprint developing performance is attributed to combined effects: (1) OP acts as an efficient “antenna” to absorb UV light and transfer energy to Eu³⁺, which allows high-intensity characteristic red emission; (2) Encapsulation in the silica gel forms a microenvironment around the Eu³⁺/OP complexes, which can reduce quenching effects of the surrounding environment; and (3) the surface of the silica gel provides numerous adhesion sites for sebaceous residues, which promotes selective deposition on ridge details and enhances contrast. Using both powder and suspension methods, fingerprints were developed with clear ridge patterns and visible level 2 and level 3 features on various porous/nonporous and smooth/rough substrates. The fingerprints aged (up to 100 days) or soaked in water (up to 50 days) were also successfully developed. These materials show great potential for forensic fingerprint development.