Strongly Fluorescent Blue-Emitting La₂O₃: Bi³⁺ Phosphor for Latent Fingerprint Detection

Area of Science:

• Materials Science
• Forensic Science

Background:

• Latent fingerprints (LFPs) are crucial in forensic investigations.
• Developing effective visualization methods for LFPs on various substrates is essential.

Purpose of the Study:

• To synthesize blue-emitting bismuth-doped lanthanum oxide (La₂O₃: Bi³⁺) phosphors.
• To evaluate their efficacy in visualizing latent fingerprints (LFPs).

Main Methods:

• Sol-gel combustion synthesis of La₂O₃: Bi³⁺ phosphors.
• Characterization using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Fourier Transform Infrared Spectroscopy (FTIR).
• Photoluminescence (PL) spectroscopy for emission analysis and powder dusting method for LFP visualization.

Main Results:

• Hexagonal structure of La₂O₃: Bi³⁺ confirmed with full bismuth incorporation.
• Strong blue emission observed around 460 nm (³P₁ → ¹S₀ transition).
• Clear, high-contrast bright-blue LFP images obtained on aluminum, compact discs, glass, wood, and marble.

Conclusions:

• La₂O₃: Bi³⁺ phosphor is an effective blue fluorescent powder for LFP visualization.
• Demonstrated visualization of all three fingerprint detail levels, including pores.
• High contrast and successful minutiae extraction confirm potential forensic applicability.