Research Highlight

Security ink

doi:10.1038/nindia.2010.8 Published online 5 February 2010

Researchers have invented a nano-sized light emitting colloid material that could be used to mark security codes and design electronic devices.

Non-aqueous light-emitting colloids based on semiconductor nanoparticles have drawbacks such as toxicity of cadmium, harmful solvents and additives. To design safer aqueous colloids, the researchers used yttrium oxide and doped it with europium, a rare-earth element. This resulted in a transparent aqueous-stable colloid nanophosphor.

A writing test showed the potential use of the transparent colloid (also called ink) for marking invisible security codes. The ink has potential application in protection of valuable documents and consumer products against fraud as also in optoelectronics, such as in the development of efficient light-emitting devices.

"It can be used for making a transparent layer on silicon solar cell to modify solar spectrum and enhance the efficiency of solar cell," says lead researcher Bipin Kumar Gupta. The cost-effective technique could also be used for bio-markers and bio-labeling.

The authors of this work are from: National Physical Laboratory, Council of Scientific and Industrial Research and Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi, India.


  1. Gupta, K. B. et al. Synthesis and characterization of ultra-fine Y2O3:Eu3+ nanophosphors for luminescent security ink applications. Nanotechnology 21, 055607 (2010) | Article |