Phase-Dependent Control of Trap Depth and Persistent Luminescence in Strontium Aluminate Phosphors

My research explores persistent luminescence materials, such as strontium aluminate singulate, and how the structure enable a bio imaging and an advanced fighting. The process of the field shows color tune vol after glow and temp, or temperature resolved luminescence from single persistent luminescence phosphor composition. To begin, weigh the SAO-B and SAO-G powders and press them under a uniaxial pressure of 3.5 tons for five minutes to form pellets.

Ensure each specimen has a uniform shape with a mass of approximately 120 milligrams, a diameter of 10 millimeters, and a thickness of one millimeter. Heat the samples at 350 Kelvin for 10 minutes to remove shallow or surface traps. Then incubate the samples at 480 Kelvin for 10 minutes to eliminate deeper traps.

Now, apply a thin uniform layer of silver paste to the sample holder surface and spread it evenly to ensure firm contact. Place the sample on the holder and wait for 10 to 15 minutes until the paste is completely dry, then mount the sample holder using the designated screws, ensuring each screw is in its correct matching position. Tighten the screws in a crosswise pattern, repeating three times to apply even pressure.

Insert the inner chamber with open holes on all sides onto the mounted sample. Next, place the external chamber over the inner chamber with the blocked window facing upward for ultraviolet visible excitation, and ensure the valve remains closed throughout this process. Switch on the vacuum pump while keeping the valve in the closed position.

Monitor the pump indicator. Observe the right light changing from red to green, and the left light from yellow to red, indicating that the pressure has dropped below one times 10 to the power of negative three millibar, then open the valve to the chamber. Now connect the fiber optic cable and adjust it to optimally collect the emitted light.

Cover the entire setup with a black blanket to block stray light and background excitation. Next, open the water supply before activating the cryostat and compressor for cooling. Switch on the temperature controller and set the heater range to 50 watts and the target temperature to 10 kelvin.

Use the displayed menu and confirm the settings twice. Now, allow the system to cool until it reaches the target temperature. Continue pumping to maintain vacuum around the sample holder.

For thermal luminescence, excite the sample with ultraviolet or visible light. After excitation, ramp the sample temperature at a controlled rate of 10 Kelvin per minute up to the desired target temperature, such as 470 kelvin, and continuously record the luminous and spectra as the temperature increases. Finally, disassemble the chamber and remove the sample holder, once the system has reached room temperature.

Upon ultraviolet excitation at 275 nanometers, SAO-B exhibited a persistent luminescence peak at 490 nanometers, while SAO-G showed a peak at 520 nanometers, confirming their blue and green emissions respectively. SAO-B demonstrated a longer decay time than SAO-G, following the same ultraviolet pre-excitation. SAO-B exhibited a thermal luminescence peak centered at 350 Kelvin, while SAO-G presented two distinct peaks at 290 Kelvin and 320 Kelvin, indicating a broader trap depth distribution.

A dual color anti-counterfeiting pattern displaying PSL made from SAO-B and SAO-G ceramics emitted blue and green colors respectively for over one hour, after ultraviolet pre-excitation. In the temperature resolved anti-counterfeiting application, the luminescence of the green labeled Chimie decreased, significantly, at approximately 100 degrees Celsius, while the blue labeled Paris remained visible. At approximately 150 degrees Celsius, the emission from the green labeled Chimie became indistinguishable, and only the blue labeled Paris remained emitting.

I identify how the crystal face control, trap depths enabling blue or green persistent luminesce with distinct DQ behavior. This work addresses the lack of dynamic time or temperature resolved persistent luminescence. My future research will focus on the new dolphins structures for tuneable lifetime, color, and biomedical applications.