A team of industrial and university researchers has shown that nanoparticles with sizes smaller than 10 nanometers – approximately the width of a cell membrane – can be successfully incorporated into scintillation devices capable of detecting and measuring a wide energy range of X-rays and gamma rays emitted by nuclear materials.
The proof-of-concept study, described in the Journal of Applied Physics, suggests that "nanocrystals" – nanoparticles clustered together to mimic the densely-packed crystals traditionally used in scintillation devices – may one day yield radiation detectors that are easy and inexpensive to manufacture, can be produced quickly in large quantities, are less fragile, and capture most of the X-ray and gamma ray energies needed to identify radioactive isotopes. Earlier studies have shown that when X-rays or gamma rays strike these miniature, non-crystalline scintillators, some atoms within them are raised to a higher energy level. These atoms de-excite and give off their energy as optical photons in the visible and near-visible regions of the electromagnetic spectrum. The photons can be converted to electrical pulses, which, in turn, can be measured to quantify the X-ray and gamma radiation detected and help locate its source.
In the latest experiment, the researchers suspended nanoparticles of lanthanum halide and cerium tribromide (loaded in both 5 percent and 25 percent concentrations) in oleic acid to create nanocomposite scintillators with sizes between 2-5 nanometers. When compared to computer models and data from prior studies, the nanocomposite detectors matched up well in their ability to discern X-rays and gamma radiation. When compared to an existing radiation detection system of similar size that uses plastic, the 25 percent loaded nanocomposite fared better than the 5 percent loaded, but still was only about half as efficient. Therefore, the researchers conclude that more work is needed to refine and optimize their "nanocrystal" system.