Defect-assisted dynamic multicolor modulation in KLu₃F₁₀:Tb crystals for anti-counterfeiting

Area of Science:

• Materials Science
• Solid-State Chemistry
• Luminescence

Background:

• Excitation-dependent dynamic multicolor luminescent materials are crucial for anti-counterfeiting.
• Conventional methods often require multiple activators in lanthanide-doped materials.
• Developing single-activator systems for multicolor emission is highly desirable.

Purpose of the Study:

• To investigate KLu3F10:Tb crystals for excitation-dependent multicolor luminescence.
• To explore the role of surface defects and citric acid (CA) modification.
• To elucidate the energy transfer mechanism responsible for multicolor emission.

Main Methods:

• Hydrothermal synthesis of KLu3F10:Tb crystals with varying CA content.
• Characterization of crystal morphology and surface properties.
• Photoluminescence spectroscopy under different UV excitation wavelengths (254 nm and 365 nm).

Main Results:

• KLu3F10:Tb crystals exhibited excitation-dependent emission.
• Green Tb3+ emission was observed under 254 nm UV excitation.
• A broadband emission at 442 nm appeared alongside Tb3+ emission under 365 nm excitation, attributed to defect states.
• Citric acid coating influenced crystal morphology and defect formation.

Conclusions:

• KLu3F10:Tb crystals demonstrate potential for excitation-dependent multicolor luminescence with a single activator.
• Surface fluorine vacancy defects play a key role in the observed multicolor emission via energy transfer to Tb3+.
• This research paves the way for advanced anti-counterfeiting technologies using simplified luminescent materials.