A novel single phase La2CaZnO5:Dy3+ phosphor for potential applications in WLED's, latent fingerprint and cheiloscopy

Abstract

Due to the distinctiveness and perseverance of the friction ridges in fingerprints (FPs), latent fingerprints (LFPs) and lip prints (LPs) are two most significant types of evidence at crime scene. Therefore, it is essential in forensic science to develop a reliable method to detect LFPs and LPs. Traditional detection methods still face a number of difficulties, such as limited sensitivity, low contrast, strong background, and complex processing stages. We proposed a method for visualization of LFPs and LPs by utilizing La2CaZnO5:Dy3+ (1–5 mol %) (LCZO: Dy) phosphor using a solution combustion method. The crystal structure, phase purity, particle morphology, photoluminescence (PL) properties of the resulting phosphors were then characterized in detail. SEM images suggested that the obtained phosphors are non-uniform shapes and agglomerated to big particles. The photophysical properties of Dy3+ doped phosphors are analyzed by exploiting their photoluminescence excitation (PLE) and emission profiles. The emission profiles of all the doped samples exhibit sharp emission lines centred at ∼481, 573, and 667 nm, which are ascribed to 4F9/2 → 6H15/2, 4F9/2 → 6H13/2, and 4F9/2 → 6H11/2 intra configurational transitions of Dy3+ ion, correspondingly. The optimum doping concentration of LCZO: Dy phosphor was 4 mol%, and the dominant factor of concentration quenching effect is the nearest-neighbor ions interaction. The chromaticity coordinates of International Committee LCZO: Dy were located in the yellow color area. In addition, LCZO: 4Dy phosphor can well visualize the LFP image and LP image. The levels 1–3 features of fingerprint and groove pattern of lip print can be easily recognised with high resolution and contrast. The experimental results showed La2CaZnO5:Dy3+ can be well applied to advanced forensic investigation.