Microwave-assisted synthesis of GdOF: Eu/Tb ultrafine phosphor powders suitable for advanced forensic and security ink applications.

The rare-earth-doped inorganic ultrafine oxyfluoride host matrices in forensic science, especially in latent fingerprint detection and anti-counterfeiting applications, were still unexplored and may replace the existing technology owing to its high sensitivity. Herein, GdOF: Eu/Tb ultrafine red and green phosphors were synthesized via a rapid, green microwave-assisted hydrothermal method at 150 °C. The phosphors synthesized by this novel method possess good luminescent intensity for the hypersensitive D→F transition of Eu and D→F transition of Tb ions as compared to the phosphors prepared via other conventional methods such as co-precipitation synthesis, sol-gel synthesis, and microwave-assisted co-precipitation synthesis. Further, an enhancement in the luminescent intensity of the ultrafine phosphor was noticed when the microwave parameters and pH values were tuned. The optimized red and green phosphors having high luminescence intensity, good color purity, and high quantum yields of 89.3%, and 71.2%, respectively, were used for the visualization of latent fingerprints on various substrates. These promising phosphors exhibited excellent visualization regardless of the background interference and limit the risk of duplication and are highly reliable. The security inks developed using these phosphors are highly efficient for anti-counterfeiting applications. These multifunctional properties of investigated phosphors can be explored for security applications.