Ascorbic acid mediated fluorescence emission of MnO₂ modified upconversion nanoparticles for anti-counterfeiting

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Counterfeiting poses a significant threat to important documents.
• Upconversion luminescence nanoparticles offer potential for anti-counterfeiting applications.
• Enhancing luminescence intensity and controllability is crucial for practical use.

Purpose of the Study:

• To develop an effective anti-counterfeiting ink using core-shell nanoparticles.
• To improve the upconversion luminescence intensity of NaYF4:Yb3+,Tm3+ nanoparticles.
• To create a system where luminescence can be reversibly switched for security features.

Main Methods:

• Synthesis of NaYF4:Yb3+,Tm3+ core nanoparticles (NPs) and NaYF4:Yb3+,Tm3+/NaYF4 core-shell NPs via high-temperature thermal decomposition.
• Fabrication of NaYF4:Yb3+,Tm3+/NaYF4@MnO2 composite NPs by physically doping MnO2 as a quencher.
• Application of the composite NPs as ink for anti-counterfeiting tests.

Main Results:

• Core-shell NPs exhibited a 2.3-fold enhancement in upconversion luminescence intensity (445-495 nm) compared to core NPs.
• MnO2 acted as an effective quencher for the upconversion fluorescence of Tm3+ ions.
• The luminescence was restored upon treatment with a reducing agent (AA), demonstrating a switchable security feature.

Conclusions:

• The synthesized NaYF4:Yb3+,Tm3+/NaYF4@MnO2 composite NPs show great promise as anti-counterfeiting ink.
• The reversible luminescence switching provides a robust mechanism for document security.
• This technology enhances information security for important documents.