New Delhi: An Indian scientist has developed a security ink that can help combat counterfeiting of branded goods, bank-notes, medicines, certificates and other important documents.
It is a highly stable and non-toxic security ink developed from nano-materials, the Union Ministry of Science and Technology said in a statement.
Sanyasinaidu Boddu, along with his team of researchers from the Institute of Nano Science and Technology, Mohali, has developed security inks that have excitation-dependent luminescent properties that are highly stable under practical conditions such as temperature, humidity and light.
The study was recently published in the journals ‘Crystal Growth and Design’ and ‘Materials Today Communications’.
Counterfeiting can be combated with the help of secret tags that use luminescent ink. Boddu and his team created security ink with nano-materials that can emit light automatically.
It is a non-toxic phosphate-based ink, and its luster can be attributed to its unique chemical properties that can help combat counterfeiting of branded goods, bank-notes, medicines, certificates and currency.
How are existing security inks different?
A technique known as downshifting controls the work of the safety ink. In this technique, the luminescent material absorbs a high-energy photon and emits a low-energy photon. Secret tags are not seen under visible light, but are visible under ultraviolet light.
Such covert tags are single emission-based tags and can be duplicated, meaning that duplicate security inks can be created. This is overcome by using luminescent inks with excitation-dependent luminescent properties. Downshifting and upconversion—the phenomenon in which the emitted photon has more energy than the excitation-causing photon—are such properties.
The possibility of decoding and repeating security ink decreases as the number of parameters required to decode a secret tag increases. This means that the number of stimulus-dependent luminescent properties should be increased. The drawback of luminescent materials currently used to design secret tags is that they are less stable and highly toxic, being made of fluoride.
Security ink developed to address the challenge
To develop the security ink, Boddu doped the Gd1-xBixPO4 nano-material with lanthanide ions. According to the ministry statement, the ink exhibited very strong downshifting and up-conversion luminescence properties.
The simple co-precipitation method was used to synthesize the luminescent nano-materials. Commercially available PVC gold medium inks and nano-materials were used to fabricate the composite. The researchers printed the patterns and letters on black paper using mixed inks. They observed the stability of the ink by studying it under different excitation wavelengths and under various conditions that arise during practical applications. The ink was found to be stable at different wavelengths under different conditions.
The developed ink has huge potential to combat counterfeiting as even a layman can easily find out whether a product is genuine or fake.
Boddu explained that the trivalent lanthanide ions have very rich energy levels that can exhibit luminescent properties, both downshifting and upconversion, according to the statement. In shear, the ink absorbs two low-energy photons and emits one high-energy photon. They postulated that the excitation-dependent downshifting emission is due to energy transfer between bismuth and lanthanide ions.
The scientist said that they decided to apply lanthanide ions for anti-counterfeiting because they are known for their excellent downshifting and upconversion luminescent properties, and can improve the protection capability.
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