X-ray-activated long persistent phosphors featuring strong UVC afterglow emissions.

Area of Science:

• Materials Science
• Solid-State Physics
• Photochemistry

Background:

• Persistent phosphors emit light after excitation, with applications in various fields.
• Existing phosphors primarily emit in visible and near-infrared ranges.
• No persistent phosphors emitting in the ultraviolet C (UVC) range (200-280 nm) were previously known.

Purpose of the Study:

• To develop a novel persistent phosphor with strong ultraviolet C (UVC) emission.
• To investigate the mechanisms behind UVC persistent luminescence.
• To explore potential applications of UVC persistent phosphors.

Main Methods:

• Synthesis of fluoride elpasolite phosphors with oxygen-induced anion vacancies.
• Experimental characterization of luminescence properties (power density, afterglow duration).
• First-principles calculations to understand defect structures and electron trapping mechanisms.
• Assessment of UVC afterglow intensity for sterilization efficacy.

Main Results:

• A new persistent phosphor exhibiting strong UVC emission was successfully created.
• The phosphor shows an initial power density >10 mW/m² and afterglow >2 hours.
• Structural defects, specifically oxygen introduction-induced anion vacancies, act as efficient electron traps.
• The UVC afterglow is sufficiently intense for sterilization purposes.

Conclusions:

• The discovery of UVC persistent phosphors opens new research avenues.
• These phosphors offer novel applications in sterilization, disinfection, drug delivery, and anti-counterfeiting.
• The understanding of defect-induced electron trapping provides a pathway for designing future persistent phosphors.