Hybrid optical nanocomposites: a low-cost solution to radiation sensors

Nanocomposites, in particular inorganic-organic hybrids, allow for a wide range of combinations of phases with broad applications including solar energy harvesting, lighting, imaging, radiation sensing, lasers, magneto-optics and plasmonics. Intense research eff orts on optical nanocomposites are being motivated by the fascinating prospect that these materials can assume the optical properties of the inorganic phase and yet be processed with the shape versatility, low-cost and ease of polymeric materials. In the area of radiation sensing for example, the United States Departments of Homeland Security (DHS) and Customs and Border Protection (CBP) have been tasked to screen every cargo container crossing domestic borders for illicit radioactive material. This is accomplished by using gamma-ray spectrometers capable of discriminating regulated special nuclear materials from non-threatening radioisotopes. To this end, scintillation detector systems, specifically thallium-doped sodium iodide (Tl:NaI) single crystals, are by far the most popular due to their reasonable performance and cost. In recent years, however, the demand for scintillator materials with improved lightyield, timing and energy resolution resulted in a wealth of new materials with att ractive properties. Remarkable single-crystals, such as Ce:LaBr₃ and Eu:SrI₂, with light outputs and energy resolution surpassing those of Tl:NaI, have been discovered but, the difficulty of their growth and size-scalability are currently limiting their commercialization. Transparent ceramic scintillators, in which CREOL’s Optical Ceramics Laboratory led by Dr. Romain Gaume is actively engaged in, off er valuable alternatives to this scalability issue. Yet, in a serendipitous research twist, Gaume’s group developed an innovative method to fabricate monolithic transparent hybrid nanocomposites with very high particle loading and high refractive index mismatch tolerance between the inorganic and organic constituents. By providing adequate radiation stopping power, such high-loading fraction composites would yet provide another means to scale-up the size of scintillation detectors.