Surface engineered La2Zr2O7:Eu3+ nanophosphors: Luminescent based platform for latent fingerprints visualization and anti-counterfeiting applications

Abstract

The advancements in the forensic technologies is still a constructive and requires continuous development and evaluation strategies are to be implement. In this regard, the present work deals with fabrication of novel surface modified red-emitting Eu3+ ions doped La2Zr2O7 nanophosphors and used for latent fingerprint visualization and data security applications. The powdered x-ray diffraction studies of the prepared samples confirm the disordered cubic phase. The photoluminescence emission spectra consist of intense emission peaks located at ∼ 576, 593, 613, 656 and 711 nm, ascribed to the 5D0 → 7FJ (J = 0 - 4) transitions of Eu3+ ions, respectively. The surface modified nanophosphors by oleic acid showed 2-fold enhancement in the emission intensity as compared to bare nanophosphors, which is due to effective intramolecular energy transfers from coordinated ligands to the activated Eu3+ ions, called the antenna effect. The photometric properties of the surface grafted nanophosphors exhibit pure red color with high purity. The visualized latent fingerprints using surface modified nanophosphor could reveal level 1 − 3 ridge characteristics, which is most reliable evidence for personal identification. High resolution images of developed latent fingerprints further validated the effective chemical binding between the hydrophobic nanophosphor and chemical constituents present in the fingerprints, which enables most authenticated sweat pores. The oleic acid grafted nanophosphors can be formulated into writable inks so that secret writings can be accomplished using a simple brush technique and decoded under ultraviolet light illumination. The followed surface modification strategy drastically improves the properties of the nanophosphor, which is real time choice for latent fingerprint development and anti-counterfeiting technologies.