Novel ‘invisible ink’ may help detect fake currency
   Date :31-Dec-2019

Novel invisible ink may h
By Shakoor Rather :
GREATER NOIDA, SCIENTISTS at Shiv Nadar University here have developed a low-cost security ink that may help detect counterfeit currency, and could be employed in official documents and medical diagnosis. The new ink, described in the peer-reviewed Journal of Physical Chemistry C, offers improved security features compared to existing inks that are multi-component and, therefore, more expensive, the researchers said. These materials can be used in other applications, such as security signs, emergency route signs, traffic signage, in addition to medical diagnosis, and background-independent bio emitting probes, they said. “Our white security ink is made from cheaper, organic compounds that can be used in daylight as they show white emission with afterglow feature covering visible range of the spectrum (400-700 nanometres) under UV light exposure,” Debdas Ray, a professor at Shiv Nadar University, told PTI.
“These single component security inks give better stability, colour reproducibility and simple device fabrication over the multi-component security inks that are costly, toxic and work under different background,” Ray said. To prepare an ink, these compounds can be mixed with commercially available cheaper transparent polymers in organic solvent or other glue-like materials, according to the researchers. It takes only 45 minutes to develop this ink which costs around Rs. 1000 per gram, the researchers said. Any characters of interest, such as symbols, pictures, shapes, bar code, etc.
Can be written on the document i.e. A white background to provide additional security, they said. “We can think about additional security in the bank note, official documents, defence security, etc,” Ray noted. After writing the characters, the document can be stored in daylight as the written characters will be invisible due to their transparent colour.