An alternative to the use of potentially harmful X-rays and ultraviolet light in security scanners is under development at the University of Sussex, U.K. Physicists are formulating a safe and efficient 'paint' that can reveal, with terahertz (THz) radiation, the contents of luggage or objects hidden in clothing.
THz radiation cannot pass through water, which is why it does not pose a health risk to living tissue, but it can penetrate fabrics, plastics and wood to give internal images similar to an X-ray.
This type of radiation falls between microwaves and infrared in the electromagnetic spectrum and travels at the speed of light, but has a lower frequency than X-rays and ultraviolet.
The researchers devised a simple demonstration that shows how the surfaces of objects up to any size can potentially be made into bright THz emitters. Thin semiconductors are bright emitters that could be 'painted' onto inexpensive materials for this application.
Instead of passing through electromagnetic scanners at airports, travelers could just walk on a pathway or near walls coated with THz-emitting ultrathin electronic semiconductors.
Other applications for such THz emitters are envisioned, including detection of art fraud by illuminating beneath the layers of paint, and countering counterfeiting in currency by incorporating ink that emits THz radiation. Medical uses could include identification of cavities in teeth or helping surgeons spot specific tumors, which have a higher water content than normal body tissue and are therefore visible under THz radiation.
The research is published in the journal Nano Energy.