DUAL EMISSIVE LUMINESCENT INK – Science is such a fascinating stream. Human life is having a dynamic development in terms of technologies. Now we have to grown to stage where even just ink can be used as a security feature. Innovation has been the need of this era.  This is because even muggers are using latest technologies. Thanks to all the brilliant minds behind the invention.

In India, in the recent past the government has banned the old  500 and 1000 rupees notes in order to bring out all the black money. And also the government has also released a new set of 500 and 2000 rupee notes. But many muggers started counterfeiting these new notes. It was a very difficult out there where it was very absurd how to differentiate the original and faked ones. Then came up the brilliant invention of “DUAL EMISSIVE LUMINESCENT INK”.


Secure ink is a type of ink which has a property called “Dual Emissive Luminescence”. This is an incredible property where in the ink changes its color on exposure to a particular type of wavelength. 

DUAL EMISSIVE LUMINESCENT INK on currency under UV light

“In the ambient light, the ink showcases white color. When exposed to UV (ultraviolet) light at 254 nm, it changes the color to red and when the UV source is switched off, it turns green”. The colors can be seen through naked eyes.

This idea was developed in the laboratory of the CSIR-IICT, where various research scientists had pushed themselves hard to achieve it.

For the production of luminescent pigment, two chemical compounds — sodium yttrium fluorite, europium-doped and strontium aluminate with europium-dysprosium — were synthesized to emit red and green colors, respectively.

The fluorescence property is through sodium yttrium fluorite, while the phosphorescence is by compound strontium aluminate.

The hydrothermal synthesis method is used to get the red color. In hydrothermal synthesis, a compound is crystallized from an aqueous solution at a high temperature.

To get the desired features of the ink, the two pigments are mixed at a weight ratio of 3 : 1. The mixture is then sintered for three hours at a temperature of 400°C. The heating process is also known as annealing. This resulted in the development of fine white powder for the single excitable dual emissive luminescent pigment.

“If we directly perform the mixing of both the phosphors (pigments) without annealing, then the individual pigments separate during ink formation and the required property of the ink to emit dual-color is not developed”.

In the last step, the powder is mixed with the polyvinyl chloride (PVC) medium to procure luminescent security ink.

Properties and applications of this ink

To analyze the stability of the DUAL EMISSIVE LUMINESCENT INK, the researchers conducted chemical tests with various bleaching agents like soap solution, ethyl alcohol and acetone.

“They studied the durability of the ink for about six months under rigorous atmospheric conditions like humid, hot and cold. Under all conditions, it remained stable, with no changes in print quality,”

Property ink of the secure ink

In addition, the viscosity of ink was tested for better printing quality. It was done on both screen and offset printing to ensure the pigment properties.  

Not just restricting itself from solving the problem of counterfeiting of currency notes, the novel ink can be used in printing documents, which have a high risk of security breach and duplication.

For example, the passport cover when seen under the UV light showcases covert emblem of India in green color. With the new ink, it will emit two colors, which is hard to copy. 

It can also be used in the pharmaceutical sector where drug companies can protect the medicines from being duplicated by printing the security features through this ink. This will ensure that there is no fraudulent practices happening by changing  the composition of the product and the consumers get authentic and safe drug.

The security feature of the luminescent ink can be used in legal confidential certificates, merchandise and electronic barcodes also to avoid duplication or sale of fake products. 

At last, we The Tech Beacon would like to give a big round of appreciation and laurels to the brilliant scientists of CSIR-IICT for showcasing an extraordinary usage of chemicals and science behind to curtail various frauds happening in our societies.

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