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.
- Paul Guss, Ronald Guise, Ding Yuan, Sanjoy Mukhopadhyay, Robert O'Brien, Daniel Lowe, Zhitao Kang, Hisham Menkara, Vivek V. Nagarkar. Lanthanum halide nanoparticle scintillators for nuclear radiation detection. Journal of Applied Physics, 2013; 113 (6): 064303 DOI: 10.1063/1.4790867
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