Lattice-engineered site symmetry control of Bi3⁺ activators for tunable luminescence and latent fingerprint detection

Optical functionality in luminous materials can be effectively tailored by manipulating the local symmetry environment of activator ions. To study the impacts of lattice engineering on photoluminescence and latent fingerprint detection, urea-assisted combustion was used to create Bi3⁺-doped Y₂O₃ phosphors co-doped with alkali metal ions (Li⁺, Na⁺, K⁺, Cs⁺). Prepared Y₂O₃ phosphors with co-doped with alkali metal ions has cubic phase with space group I –a 3 with dopant-induced lattice contraction and smaller crystallites. In FTIR study we observed vibrational bond due to Y-O stretching. Prepared phosphor has irregular particles size with average particle size ~140 nm. Bi3+ ions occupy C₂ and S₆ symmetry positions, according to optical investigations, resulting in separate 1S₀→3P₁ and 1S₀→1P₁ transitions. Alkali co-doping increased intensity without changing the spectrum, however emission changed from bluish-white (329–337 nm excitation) to blue (374 nm). Y₂O₃: Bi/Na demonstrated exceptional fingerprint visualization and nearly 100% color purity. These findings demonstrate that tunable luminescence for sophisticated photonic and forensic applications is made possible by Bi3⁺ site-symmetry modification via alkali lattice engineering.