Bright red luminescence from Eu3+-activated noncytotoxic SnO2 quantum dots for latent fingerprint detection

Abstract

Ravishing red luminescent Eu3+-activated SnO2 quantum dot (QD) phosphors were successfully synthesized by employing a simple chemical reduction method. X-ray diffraction analysis confirmed that the Eu3+:SnO2 QDs have a tetragonal structure. The particle size, interplanar distances, and elements existing in the sample were examined by performing transmission electron microscopy, high-resolution transmission electron microscopy, and elemental mapping studies, respectively. Under UV illumination, photoluminescence analyses were performed on pristine SnO2 QDs and Eu3+:SnO2 QDs. Under 294 nm of excitation, a broad emission band was observed for the undoped SnO2 QDs centered at 454 nm. A robust red emission emitted from the Eu3+-activated SnO2 QDs by excitation at 394 nm. The red emission intensity was significantly enhanced by increasing the Eu3+ ion concentration up to 0.3 mol%, and it was decreased drastically by increasing at above 0.3 mol% of Eu3+ ions due to concentration quenching. Furthermore, an energy migration was observed from SnO2 QDs host to Eu3+ ions. The International Commission on Illumination (CIE) color coordinates, correlated color temperature, and color purity values were evaluated for all the Eu3+:SnO2 QDs based on the emission profiles. The obtained CIE coordinates were compared with the standard National Television System Committee coordinates. Additionally, the applicability of the Eu3+:SnO2 QDs was evaluated to visualize the latent fingerprints on smooth surfaces using the powder dusting method. The obtained latent fingerprint images exhibited good sensitivity, high contrast, and appreciable ridge details. The noncytotoxicity of the Eu3+:SnO2 QDs was confirmed by conducting a toxicity test on normal fibroblast cell lines (L929). The results revealed that the noncytotoxic and ravishing luminescent Eu3+:SnO2 QDs can garner significant interest for use in latent fingerprint, biological labeling, imaging, and security encoding. We believe that such a method of producing lanthanide-doped QDs can accelerate the development of QD phosphor-based research.