Design of Bi-functional composite core-shell SiO2@ZnAl2O4:Eu~(3+) array as a fluorescent sensors for selective and sensitive latent fingerprints visualization protocol

摘要

Core-shell SiO2@ZnAl2O4:Eu~(3+) (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 ~5D_o → ~7F2 transition of the Eu~(3+) 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 ～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:Eu~(3+) (5 mol%) NP can be used as an ideal candidate for multifunctional applications such as WLEDs, LFPs, anticounterfeiting etc.