Dual-Functional Li⁺-Sensitized Gd₂O₃:Dy³⁺ Nanophosphor for Near-UV White Light Emission and Latent Fingerprint Visualization

Trivalent rare earth (RE 3+ )-doped luminescent phosphors are crucial for optoelectronic and forensic applications. We report the synthesis of Gd 2 O 3 :xDy 3+ nanophosphors (1˂ x ˂ 3 wt%) and Li + co-doped Gd 2 O 3 :2wt%Dy 3+ :yLi + (0.5˂ y ˂ 3 wt%) nanophosphors via solution combustion method at 773 K utilizing citric acid as fuel. XRD analysis reveals that Gd 2 O 3 :xDy 3+ samples form a pure cubic phase only after annealing above the synthesis temperature of 773 K, and Li + co-doped samples display a pure cubic phase at the synthesis temperature itself. The TEM analysis reveals the changes in the surface morphology due to Li + incorporation. The XPS data corroborate the presence of Gd, O, Dy, and Li elements in the nanophosphors. Integration of the Li + ions brings about a noticeable rise in optical bandgap, improves crystallinity, and oxygen vacancy formation. Dy³⁺-activated phosphors emit white light through blue, green, and red transitions under 349 nm excitation. Optimal emission occurs at 2 wt% Dy³⁺, and Li⁺ co-doping enhances its intensity by ∼2.1 times. The average lifetime of Dy³⁺ levels also increase with Li⁺ co-doping. The optimal sample shows CIE coordinates of (0.375, 0.395), a CCT of 4276 K, and 31% colour purity. Additionally, these phosphors effectively visualize latent fingerprints under UV light. Due to their efficient white emission, these nanophosphors are potential candidates for white LEDs and forensic applications.