Photoluminescent europium(III) complex intercalated in natural and synthetic clay minerals for enhanced latent fingerprint detection

Fluorescent nanohybrid materials, europium(III) complex intercalated Na super(+)-smectite clay minerals (synthetic hectorite and natural montmorillonite), have been developed to visualize latent fingerprints. The guest europium(III) complex ([EuCl sub(2)(Phen) sub(2)(H sub(2)O) sub(2)]Cl .H sub(2)O) was obtained by simple complex reaction between europium chloride hexahydrate (EuCl sub(3).6H sub(2)O) and 1,10-phenanthroline (Phen) as a 1:2 molar ratio of Eu super(3 +) ion to ligand molecules. The intercalated nanohybrids ([Eu(Phen) sub(2)] super(3 +)-clay minerals) were obtained through ion exchange reaction of interlayer sodium cation with europium complex ion. Guest europium(III) complex and [Eu(Phen) sub(2)] super(3 +)-clay mineral hybrids were characterized by powder X-ray diffraction, Fourier transform infrared, thermogravimetry-differential thermal analysis (TG-DTA), elemental analysis, UV-visible and fluorescence spectroscopy. The intercalated complex maintains a characteristic red super(5)D sub(0)- super(7)F sub(2) emission at wavelength 617 nm, which is comparable to that of the free complex. The super(5)D sub(0)- super(7)F sub(2) emission intensity of [Eu(Phen) sub(2)] super(3 +)-laponite was ca. 3.5 times higher than that of [Eu(Phen) sub(2)] super(3 +)-montmorillonite, due to the presence of quenching impurities in natural montmorillonite itself. Fingerprint residues on glass slides were harvested by using [Eu(Phen) sub(2)] super(3 +)-clay mineral powders, resulting in good definition for enhanced latent fingerprint detection. Particularly, [Eu(Phen) sub(2)] super(3 +)-hectorite hybrid powder was more clearly separated from the background compared to the montmorillonite hybrid powder.