New Delhi: An Indian scientist has developed a security ink that can help combat the 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 & Technology said in a statement.
Dr Sanyasinaidu Boddu, along with his team of researchers from the Institute of Nano Science and Technology, Mohali, has developed the security ink that has excitation-dependent luminescent properties that are highly stable under practical conditions such as temperature, humidity, and light.
The study was recently published in the 'Crystal Growth and Design' and 'Materials Today Communications' journals.
Counterfeiting can be combated with the help of covert tags that use luminescent ink. Boddu and his team made the security ink with nano-materials that can spontaneously emit light.
It’s a non-toxic phosphate-based ink, and its luminescence can be attributed to its unique chemical properties that can help combat the counterfeiting of branded goods, bank-notes, medicines, certificates and currency.
How Are Existing Security Inks Different?
A technique known as downshifting governs the working of security inks. In this technique, the luminescent material absorbs a high-energy photon and emits a low-energy photon. The covert tags are not seen under visible light, but become visible under ultraviolet light.
Such covert tags are single emission-based tags and can be replicated, meaning that duplicate security inks can be created. This is overcome using luminescent ink with excitation-dependent luminescent properties. Downshifting and upconversion — the phenomenon in which the photons emitted have higher energy than the photons that caused the excitation — are such properties.
The possibility of decoding and replicating the security inks decreases when the number of parameters required to decode the covert tag increases. This means the number of excitation-dependent luminescent properties must be increased. The drawback of the luminescent materials used currently to design covert tags is that they are less stable and highly toxic because of being made up of fluorides.
The Security Ink Developed To Address The Challenge
To develop the security ink, Boddu doped Gd1-xBixPO4 nano-materials with lanthanide ions. The ink exhibited very strong downshifting and upconversion luminescence properties, according to the ministry’s statement.
Simple co-precipitation method was used to synthesise the luminescent nano-materials. Commercially available PVC gold medium ink and the nano-materials were used to make a composite. The researchers printed patterns and letters on black paper using the composite ink. They observed the stability of the ink by studying it under different excitation wavelengths, and subjecting it to various conditions which may arise during practical applications. The ink was found to be stable at the wavelengths, under different conditions.
The developed ink has huge potential to combat counterfeiting because even a common man can easily find out if a product is original or fake.
Boddu explained that trivalent lanthanide ions have very rich energy levels that can exhibit both downshifting and upconversion luminescent properties, according to the statement. In upconversion, the ink absorbs two low-energy photons and emits a high energy photon. The excitation-dependent downshifting emission occurs due to energy transfer between bismuth and lanthanide ions, he added.
The scientist said 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 security ability.