Synthesis and Characterization of Luminescent Nanomaterials Based on Lanthanide ions and Their Applications for Latent Fingerprint Detection

Abstract

Pure lanthanum titanate doped with europium metal ions (La2Ti2O7:Eu3+‏) and dispersed in silica matrix phosphor powder was prepared by sol-gel process followed by thermal treatment. The effects of silica, thermal treatment, Eu3‏+ ion, and surfactant (CTAB) concentrations on the crystal, morphology, and photoluminescence properties (PL) were investigated. The present work found that dispersion of La2Ti2O7:Eu3+‏ into silica matrix significantly altered the morphology of La2Ti2O7:Eu3+‏ from high crystalline micro-plate like shape into amorphous aggregated nano-spherical shape. The high separated spherical shape with intense red PL emission and long lifetime was obtained from 10 mol% Eu3‏+:La2Ti2O7‏ dispersed into silica matrix, and prepared in the presence of CTAB. After optimization the preparation conditions in case of using Eu3+ as a dopant, the PL properties of La2Ti2O7 dispersed into silica matrix was doped with other different lanthanide ions such as Tb3+, Eu3+, Sm3+, Dy3+ and Er3+ ions were studied. Also, the effect of another preparation method (hydrothermal method) under different hydrothermal preparation conditions such as hydrothermal temperature (120, 160, 200oC for 72 h), time (24, 48, 72 at 200oC) and CTAB concentrations (0, 0.04, 0.1 x 10-2 mol) on the structural, morphology and PL properties were studied. The XRD results reveal that the crystalline La2Ti2O7 phase formed into amorphous silica at hydrothermal temperature and time equal 200oC and 72 hrs, respectively. By increasing hydrothermal time and temperatures, the amorphous silica tend to grow from amorphous silica contains spherical Eu3+:La2Ti2O7 nanoparticle in their nanopores to nano flak and branched wire like shape at hydrothermal time = 72 hrs and temperature = 200 oC. The high PL intensity, asymmetry ratios and lifetime were observed in case of sample prepared at 200oC for 72 hrs in the absence of CTAB.