Development of red-emitting Ba2LaSbO6:Mn4+ phosphors for latent fingerprint detection

Latent fingerprints provide crucial affirmations of identity in forensic science. However, they are microscopic. In this study, novel fluorescence materials, Ba2LaSbO6:Mn4+ (BLSO:Mn4+) phosphors, were developed by a sol–gel method for the fluorescence imaging of latent fingerprints. The structural properties of the phosphors were investigated by powder X-ray diffraction (XRD) and its Rietveld refinement analyses, and transmission electron microscopy and scanning electron microscopy techniques. The photoluminescence properties of the BLSO:Mn4+ phosphors were evaluated comprehensively by recording the emission, excitation, and decay curves. The BLSO:Mn4+ phosphors provide a high-intensity red emission at 677 nm under 350 nm excitation caused by the 2Eg→4A2g transition of Mn4+. The optimum concentration of Mn4+ in the BLSO host was determined to be ~0.2 mol%. The calculated Commission International de L'Eclairage (CIE) chromaticity coordinates (0.716, 0.283) of the emission from the BLSO:Mn4+ phosphor are located in the pure red region of the CIE 1931 diagram. The red-emitting BLSO:0.2Mn4+ phosphor was used as a fluorescence imaging powder for visualizing latent fingerprints on various substrates with high resolution, high contrast, and high efficiency, as well as good selectivity.