Research Highlight

Security ink to stop fake currency notes, illegal drugs

doi:10.1038/nindia.2018.5 Published online 16 January 2018

Researchers have synthesised a light-emitting ink that can be used to develop security codes to stop the production of fake currencies, illegal drugs and fraudulent copying of vital documents1.  

Counterfeiting causes huge financial losses in the pharmaceutical and financial sectors. Organic dyes and semiconductor quantum dots are widely used to generate unbreakable security codes, but dyes are unstable and quantum dots are toxic.  

In search of a better security ink, scientists from the CSIR-National Physical Laboratory (CSIR-NPL) in New Delhi, led by Bipin Kumar Gupta, prepared a security ink by mixing nanorods of rare-earth elements with light-emitting solids made of zinc and manganese in a specific polymer-based ink. They then tested the ink’s potential to check counterfeiting by printing specific security codes on black paper.

When exposed to ultraviolet light and infrared laser, the ink emitted yellow and red light. The nanorods gave off the red light and the light-emitting solids contributed to yellow emission, indicating that the components of the ink retained their individual optical properties even in a mixed condition. 

The ink was then successfully used to generate security codes for the national emblem and a logo of a CSIR institute on black paper, suggesting its potential for use in combatting fraudulent imitations.  

The scientists now plan to make security ink for generating codes for mobile-based scanners, to provide full protection against counterfeits, says Gupta.


1. Nagpal, K. et al. A novel approach to synthesise a dual-mode luminescent composite pigment for uncloneable high-security codes to combat counterfeiting. Chem. Eur. J. 23, 17144–17151 (2017)