The new security ink contains two pigments that emit different colours at very different wavelengths to curb fake printing of passports & currency notes.

Indian Currency Notes 2000 - 500

Researchers at the Delhi-based CSIR-National Physical Laboratory have developed a bi-luminescent security ink to crack down counterfeiting of currency notes, and fake printing of passports & pharmaceuticals. The ink was made in a batch of one kg and given to the Bank Note Press (BNP) in Dewas, Madhya Pradesh.

The BNP is a unit of Security Printing Minting Corporation of India Ltd. (SPMCIL).

As per report published in the Journal of Materials Chemistry C, the novel security ink emits intense red colour when exposed to 254 nm wavelength UV and emits green colour soon after the UV source is turned off.

Note: Currently, the Indian currency notes display only one color with the emission of wavelength.


Facts: Bi-luminescent Security ink

The new security ink contains two pigments that emit different colours at very different wavelengths when exposed to UV light of a particular wavelength to curb fake printing of passports & currency notes.

Dr. Bipin Kumar Gupta from NPL said:

The emission of red is due to fluorescence while green is due to phosphorescence phenomenon. Both red and green can be clearly seen with the naked eye under ambient conditions.

The red colour is emitted at 611 nm wavelength while the green is emitted at 532 nm. The ink has the potential to be used as a security feature on currency notes and passports.

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How novel security ink created?

  1. The team of scientists first synthesized the pigments that emit red and green colours.
    • For synthesising the red pigment, sodium yttrium fluorite doped with europium through hydrothermal method.
    • For the green pigment, they mixed strontium aluminium oxide and doped it with europium and dysprosium.
  2. Then, the red and green pigments synthesized separately are mixed in 3:1 weight ratio and heated to 400 degree C for three hours.

Finally, the ink is prepared by dispersing the two pigments that have been mixed at a high temperature in a commercially available Polyvinyl chloride (PVC) medium and vigorously stirred for an hour.

Why the need of security ink?

After demonetization, the Reserve Bank of India (RBI) has frequently released the new banknotes  – ₹10, ₹20, ₹50, ₹100, ₹500, ₹2000 – with changed designs & adding many security features in our country. Despite these precautions, many of the reports hinted that fake notes are still being circulated in India.

Indian Currency 500 Notes
Indian Currency 500 Notes

Central bank’s annual report 2019: Counterfeit notes detected in FY19

Out of the total Fake Indian Currency Notes (FICNs) detected in the banking sector, 5.6% were detected at the RBI and 94.4% were detected by other banks.

  • Counterfeit of –
    1. New ₹500 notes increased by 121%.
    2. New ₹2000 denomination increased by 21.9%.
    3. New ₹100 rupee declined by 7.5% (but remained the denomination with the highest number of counterfeits).

Fluorescence & Phosphorescence

Both fluorescence and phosphorescence are spontaneous emissions of electromagnetic radiation.

  • The glow of fluorescence stops right after the source of excitatory radiation is switched off.
  • Phosphorescence continue to emit light up to many hours after the end of external illumination.

Source: PIB

Megha Jain

Engg & Freelance Author

Straight forward