Design of Bi-functional composite core-shell SiO2@ZnAl2O4:Eu3+ array as a fluorescent sensors for selective and sensitive latent fingerprints visualization protocol

Core-shell SiO2@ZnAl2O4:Eu3+ (5 mol%) nanophosphor (NP) with coatings up to the level IV has been prepared by a facile solvothermal route, followed by heat treatment. Scanning electron microscopy studies of fabricated core-shell particles displays good spherical shape and non-agglomeration with a narrow size distribution. The thickness of the shell increased with increase in coating cycles. Photoluminescence (PL) studies exhibited strong red emission peaks at 612 nm corresponding to the D-5(0) -> F-7(2) transition of the Eu3+ ions. PL intensity increased with calcination temperature and coating cycles. The color coordinates of the coated NP were turned towards intense pure red emission with color purity similar to 95%. Powder dusting method was used to visualize latent fingerprints (LFPs) by staining uncoated and coated NP on various porous and non-porous surfaces under UV light. It was clear that core-shell NP display high sensitivity, reproducibility, selectivity, reliability, and can obtain the complete three levels of fingerprint ridge details. Judd-Ofelt (J-O) intensity parameters and radiative properties, namely transition probabilities, radiative lifetimes, branching ratios, and quantum efficiency were evaluated. The aforementioned results established that the SiO2@ZnAl2O4:Eu3+ (5 mol%) NP can be used as an ideal candidate for multifunctional applications such as WLEDs, LFPs, anticounterfeiting etc. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.