This research developed a security ink based on gap-enhanced Raman tags (GERTs) that is invisible to the naked eye but detectable through highly specific SERS signals using Raman spectroscopy. The optimized ink produces strong, uniform, and stable Raman signals.
By tuning the concentrations of HAuCl4 and HEPES, the researchers balanced SERS enhancement and colloidal stability. In a demonstration, the invisible word “CHULA” handwritten on filter paper was successfully revealed using Raman imaging.
The encoded patterns remained detectable after one year under ambient conditions, highlighting the potential of GERT inks for anti-counterfeiting, document authentication, and molecular-level security encoding.
- Boonphop Chaisrikhwun
- Pornnapat Auttavetin
- Attasith Parnsubsakul
- Sanong Ekgasit
- Prompong Pienpinijtham