Fluorescent Organohydrogel for Encrypting Secret Information

Fluorescence – the phenomena where some materials emit radiation as a result of external stimuli – is usually a result, at least in the authentication industry, of visible light being emitted from incident radiation of a shorter wavelength.

The classic example in security printing, which is popular in providing a good level of protection from casual counterfeiting, are the fluorescent inks which are typically not visible when viewed in white light but emit light of a single visible colour when excited by a UV lamp.

A different approach, however, has been adopted by the Smart Polymer Materials group led by Prof Chen Tao at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS). The research team, in collaboration with scientists from Beihang University, has developed a fluorescent organohydrogel which could serve as an effective platform for the encryption and decryption of secret information.

The study, titled ‘Heterogeneous Fluorescent Organohydrogel Enables Dynamic Anti‐Counterfeiting’ ¹ was published in September 2021 in Advanced Functional Materials.

In this study, a fluorescent organohydrogel is fabricated through a two-step interpenetrating technique, leading to the co-existence of a hydrophilic network emitting green-yellow fluorescence and a hydrophobic network with photochromic capability.

As a result of these unique heterogeneous networks, the fluorescing colour goes through a continuous change from green to yellow to red via the fluorescence resonance energy transfer (FRET) process, with the extension of irradiation time.

In addition, by selective treatment with H+ solution (hydrogen ions), the fluorescent organohydrogel can act as an effective platform for encrypting secret information, making it even more difficult to counterfeit.

1 - https://onlinelibrary.wiley.com/doi/10.1002/ adfm.202108365.