Ionic Conduction-Based Polycrystalline Oxide Gamma Ray Detection - Radiation-Ionic Effects.

Newly discovered opto-ionic effects in metal oxides provide unique opportunities for functional ceramic applications. The authors generalize the recently demonstrated grain boundary opto-ionic effect observed in solid electrolyte thin films under ultraviolet (UV) irradiation to a radiation-ionic effect that can be applied to bulk materials and used for gamma-rays (γ-rays) detection. Near room temperature, lightly doped Gd-doped CeO2, a polycrystalline ion conducting ceramic, exhibits a resistance ratio change ≈103 and reversible response in ionic current when exposed to 60Co γ-ray (1.1 and 1.3 MeV). This is attributed to the steady state passivation of space charge barriers at grain boundaries, that act as virtual electrodes, capturing radiation-induced electrons, in turn lowering space charge barrier heights, and thereby exclusively modulating the ionic carrier flow within the ceramic electrolytes. Such behavior allows significant electrical response under low fields, that is, < 2 V cm-1, paving the way to inexpensive, sensitive, low-power, and miniaturizable solid-state devices, uniquely suited for operating in harsh (high temperature, pressure, and corrosive) environments. This discovery presents opportunities for portable and/or scalable radiation detectors benefiting geothermal drilling, small modular reactors, nuclear security, and waste management.

New Iron Oxide Nanoparticles Catechol-Grafted with Bis(amidoxime)s for Uranium(VI) Depletion of Aqueous Solution.

Environmental pollution caused by heavy metals constitutes a serious public health problem. In the case of uranium depletion, amidoxime groups are important because of their high affinity for uranium(VI). New series of bis(amidoxime)s with catechol-derived anchor groups were tested (b-AMD-1 and b-AMD-2). The catechol groups were designed to bind to the surface of maghemite nanoparticles (MNPs), and two nanohybrid devices MNP-b-AMD-1 and MNP-b-AMD-2 were obtained. This strategy makes for efficient removal of U(VI) via its complexation with the bis(amidoxime)s (b-AMD) and also its extraction from aqueous solution by magnetic harvesting of the MNPs. The assynthesized and b-AMD-grafted MNPs were characterized by several techniques: X-ray diffraction (XRD), high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM), X-ray photoelectron spectrophotometry (XPS), thermal analysis (TG/DTA) and Fourier transform infrared spectroscopy (FTIR). Sorption tests were run at pH 6.5, which corresponds to the highest affinity and selectivity of b-AMD for U(VI). After magnetic separation, the chelation ability and the selectivity of MNP-b-AMD-1 and MNP-b-AMD-2 towards U(VI) were evaluated by measuring the residual U(VI) concentration in the supernatant by inductively coupled plasma-mass spectrometry (ICP-MS). The data were plotted according to the Langmuir and Freundlich isotherms; the maximal sorption capacity (qmax) was 29 and 60 mg U g-1 for MNP-b-AMD-1 and MNP-b-AMD-2, respectively. This confirms that bis(amidoxime) groups are good candidates for uranium depletion of aqueous solution.