To prevent security breaches related to nuclear materials, the ability to detect and confirm changes to nuclear devices or material remains vitally important. But conventional approaches using traditional radiation dosimetry are often slow, expensive, unnecessarily complex, and require a power source at the instrument. Dosimetry methods also require close proximity to the material source, which can end up exposing the detection electronics themselves to radiation.

PNNL researchers have invented a nanoplasmonic film that overcomes such problems. Nanoplasmonic materials change when exposed to different levels of radiation—an indication that the underlying material has been altered.

PNNL’s nanoplasmonic film is less than one-micron thick. The film consists of a layer of spherical, radiation-sensitive nanoparticles on top of a flexible substrate. The spheres are coated with a noble metal, such as gold, to create nanoshells. Each metallic nanoshell is a tiny optical antenna with a reflectance profile that varies with wavelength. Any change in radiation level shifts the film’s wavelength profile. The amount of the shift is proportional to the change in radiation dose. A low-energy optical probe can measure the change from 10 to 100 meters away and no power is required at the source.

Compared to conventional thin films, PNNL’s nanoplasmonic film was more sensitive to wavelength shifts from irradiation in proof-of-concept tests. Based on a film originally created for energy savings and window applications, the material can be fabricated at very little cost. When applied to packaging or containers, PNNL’s new film represents a safe, simple, effective, and low-cost option for identifying potential security breaches related to arms control and special nuclear material tracking applications.