ZnO Nanoparticles’ Fluorescence-Specific Emission Profile

• Fluorescence emission only under UV excitation in 260-365 nm range.
• Sharp near band-edge emission at 378 nm.
• Broad green emission at 520 nm due to deep level emission (DLE).
• Useful for anti-counterfeiting applications due to UV- excitation.
• Blind to visible wavelengths, i.e. 400-700 nm

ZnO Nanoparticle Size and Distribution

• Average size: 4-5 nm, particle size distribution: 2 nm.
• Smaller sizes and modified surface properties improve fluorescence efficiency and stability .
• Similar size with different fluorescent properties are crucial for anti-counterfeiting inks application.

ZnO Nanoparticles’ Tunable Emission Profile

• Photoluminescence emission tunable between violet to green.
• Color adjustment based on DLE to NBE emission ratio.
• Enhances ink versatility for various security applications.

Reagent-Free and One-Step Synthesis of ZnO Nanoparticles

• Utilizes femtosecond laser ablation in liquid (fs-PLAL) method for synthesis.
• Process includes pelletizing ZnO powder, sintering at 700-900°C for 22-26 hours, laser ablation in a solvent, and centrifuging for uniform particle size distribution.
• This reagent-free method simplifies production, reduces costs, and minimizes environmental impact.

ZnO Nanoparticles’ Deep Level Emission Control (Green emission)

• Adjust pulse duration and ablation power during synthesis.
• Enhance DLE emission by varying laser ablation power from 0.5 W to 1.5 W.
• Maintain pulse duration between 500-600 fs.
• Fine-tune green emission for anti-counterfeiting ink fluorescence characteristics.

ZnO Nanoparticles as Fluorescent Anti-Counterfeiting Ink

• No additional binders or additives needed. Simple, cost-effective process.
• Ideal for currency, documents, products. Offers hidden security under UV light.