SciNapS

In order to respect the nuclear non-proliferation treaty and in a dreadful resurgence of terrorism, the detection and identification of nuclear and radioactive (N/R) material is a crucial issue. This N/R surveillance is achieved through scintillating materials, which convert incident radiation into visible scintillation photons. Territory surveillance is then ensured via the deployment of radiation portal monitor with embedded plastic scintillators (PSs) as displaying the following benefits: large-scale and low-cost production, outdoor condition resistance (not hygroscopic, low-temperature sensitivity) and wide tunability towards different type of radiations. The main technological barrier of this type of sensors remains their low stopping power of high-energy radiation. As primary composed of carbon, hydrogen and oxygen atoms, PSs have a low effective atomic number (Zeff) which significantly reduces their stopping power against high-energy gamma radiation and thus deteriorating the identification information on the output signals (absence of the characteristic total absorption peaks). Previous strategies reported organometallic of bismuth or lead to increase the Zeff of PSs, but increasing amounts of organometallics in PSs caused a significant loss of luminescence yields. Recent studies have established a proof of concept on the use of high atomic number (Z) nanoparticles and their high doping rate into NanoComposite Scintillators (NCSs). These developments could broaden the PSs scope of applications such as medical diagnostic. The SciNapS project aims to develop other types of Zeff-enhanced NanoComposite Scintillators via high-Z nanophotonic materials and their loading at high amount into plastic matrices. Several nanomaterials will be studied such as Cerium-doped fluoride nanocrystals (La1-xCexF3, LiGd1-xCexF4), Quantum Plates (CdSe/CdS, CdS-ZnSe) and mono-, bi- or trimetallic nanoparticles of gold, silver and platinum. For each type of nanomaterial, Monte-Carlo simulations will identify the best candidates and optimize their dispersion conditions (i.e. inter-object distance, doping rate). The synthesis of the nano-objects (i.e. composition, structures, sizes) and their surface modification (heat treatment, adapted core/shells (CdS, ZnS), polymerizable surfactants) will allow fine adjustment of their photonic features (i.e. absorption and emission wavelengths, quantum yield, fluorescence lifetime) as well as their dispersion at high amount (superior to 20wt%, ideally superior to 50wt%) in aromatic monomer matrices such as styrene. NCSs will then be produced based on similar procedures from PSs or by developing new approaches if necessary, then analyzed toward their structural nature (SAXS), photonics features (lifetime, FRET, quantum yield) and gamma ray response (radioluminescence yield, presence of characteristic total absorption peaks). A benchmark study and a market survey will then be carried out on the best NCSs candidates. Then will follow, if applicable, scale up studies towards nanomaterials and NCSs higher-volumes production. The SciNapS project will gather three academic teams (Chemical Research Institute of Paris (IRCP), Léon Brillouin laboratory (LLB), CEA-LIST), one start-up (Nexdot) specialized in quantum plates development and production and one industrial leader on PSs production (Nuvia). This multidisciplinary consortium thus offers a large network of French academic, enterprising and industrial research.