Bright red-luminescence of Eu3+ion-activated La10W22O81 microphosphors for noncytotoxic latent fingerprint imaging

초록

An intense red emission from Eu3þ: La10W22O81 (LWO) microphosphor rods has been obtained under UV excitation source for latent fingerprint (LFP) imaging. Microphosphor rods of LWO doped with various concentrations of Eu3þ ions were synthesized using a hydrothermal assisted solid-state method. XRD revealed that the microphosphors had an orthorhombic structure with the space group of Pbcn (60). FESEM showed that the surface morphology of the optimized Eu3þ (14 mol %): LWO microphosphors were hexagonal rods with pencil-like tips at both ends. TEM evaluation with elemental mapping and XPS analysis confirmed the occurrence of the vital elements in the microrods. FTIR spectral analysis was performed for the analysis of the spectral bands. An intense red emission was obtained from the Eu3þ doped LWO microphosphors under the excitation of 394 nm (7 F0/5 L6) which could be attributed to the hypersensitive transition of 5 D0/7 F2 pertaining to the Eu3þ ions. Enhancement of the emission was noticed from the microphosphors when the Eu3þ content was increased. Optimal red emission was obtained with the Eu3þ (14 mol %): LWO microphosphor. The photoluminescence intensity was found to be reduced after optimized concentration due to concentration quenching. The quadrupoleequadrupole interaction is found to be responsible for concentration quenching. The luminescent properties were systematically demonstrated using an energy level scheme diagram. The luminescence lifetime was evaluated for all the concentrations of Eu3þ doped LWO samples. The lifetime decay dynamics has also been clearly elucidated. CIE color coordinates were also evaluated from the luminescence spectra of the microphosphors and they are found to be located in strong red region. A significant luminescence quantum yield was determined for the Eu3þ (14 mol %): LWO microphosphor. The optimized microphosphor was used in detecting LFPs, employing the powder dusting method commonly used in forensic science. We detected the LFP ridge patterns with high sensitivity, reliability, and selectivity by using the optimized microphosphor. Its non-cytotoxic nature was also evaluated using WI-38 cell lines. Results demonstrated that the Eu3þ (14 mol %): LWO microphosphor could be a promising candidate for luminescent applications and LFP applications in forensic investigation preferably.

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