New design of highly sensitive and selective MoO₃:Eu³⁺ micro-rods: Probing of latent fingerprints visualization and anti-counterfeiting applications

Red colour light emitting Eu³⁺ ions activated MoO₃ nanophosphors (NPs) were prepared through an ultrasound assisted sonochemical method using Aloe Vera (A.V.) gel as a bio-surfactant. Properties like crystal structure, morphology, optical band gap, luminescent properties, radiative parameters of prepared samples and their use in latent fingerprint (LFPs) visualization were reported. Powder X-ray diffraction results revealed the single orthorhombic crystal structure of the prepared samples, which specifies effective substitution of dopant ions. Morphology of NPs exhibits the hexagonal rod-like structures with size of ∼10 nm. Photoluminescence (PL) emission spectra exhibited sharp, intense peaks at ∼539 nm, 593 nm, 615 nm, 651 nm and 702 nm attributed to ⁵D₀ → ⁷F₀, ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂, ⁵D₀ → ⁷F₃ and ⁵D₀ → ⁷F₄ transitions of Eu³⁺ ions respectively. Judd-Ofelt (J-O) theory was used to estimate the PL intensity parameters and Eu-O ligand behavior. The International Commission on Illumination coordinates of the prepared samples located in the pure red region. The optimized sample can be explored as a novel sensing material for the visualization of LFPs on various surfaces under 254 nm UV light. Clear level-3 patterns (sweat pores) were observed in the LFPs and their decay was very slow compared to the LFPs obtained from commercial powders. The photometric characterization of the prepared samples reveals the suitability of the MoO₃:Eu³⁺ NPs for pure red emission in light-emitting diode, better visualization of LFPs and anti-counterfeiting applications.