Recent developments in medical imaging techniques, in particular, those in time-of-flight positron emission tomography put new challenges on scintillating material performance that cannot be fulfilled by conventional scintillators. Bright and ultrafast nanoparticles represent promising candidates to build up an advanced detection system needed. We synthesize colloidal CsPbBr3 nanoplatelets emitting blue light with fast sub-nanosecond decay. We also prepare a nanocomposite material by embedding the nanoplatelets in the polystyrene matrix. We show that blue emission is preserved provided the composite is not exposed to UV/vis light and/or elevated temperatures. Motivated by conflicting information from the literature about the room temperature structure of colloidal CsPbX3 (X = Cl, Br, I) particles, that results being orthorhombic, rather than cubic, we perform ab initio electronic structure calculations of bulk crystals with an orthorhombic structure. We calculate optical properties, as well as exciton diameters and binding energies and compare them to those previously obtained for cubic CsPbX3 crystals.

Nanocrystals of CsPbBr3 have been incorporated in a polystyrene matrix with 1–10% weight filling factors. Samples were characterized with the main focus on their timing capability under soft X-ray irradiation for application as ultrafast scintillation detectors.

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International audienceThe electron transfer from oxide into water is studied in nanoparticle suspensions of various oxides (SiO2, ZnO, Al2O3, Nd2O3, Sm2O3, and Er2O3) by means of pulse and γ radiolysis. The time-resolved and steady-state investigations of the present study demonstrate independently that whatever the band gap and the electron affinity of the oxide, the electron transfer always takes place in these nanometric systems: Irradiation generates hot electrons which have enough energy to cross the semiconductor–liquid interface. Moreover, picosecond measurements evidence that the spectrum of the solvated electron is the same as in water. Lastly, the decay of the solvated electron is similar on the picosecond to nanosecond time scale in water and in these suspensions, but it is clearly different on the nanosecond to microsecond time scale

Highly luminescent ZnO:Ga-polystyrene composite (ZnO:Ga-PS) with ultrafast subnanosecond decay was prepared by homogeneous embedding the ZnO:Ga scintillating powder into the scintillating organic matrix. The powder was prepared by photo-induced precipitation with subsequent calcination in air and Ar/H₂ atmospheres. The composite was subsequently prepared by mixing the ZnO:Ga powder into the polystyrene (10 wt% fraction of ZnO:Ga) and press compacted to the 1 mm thick pellet. Luminescent spectral and kinetic characteristics of ZnO:Ga were preserved. Radioluminescence spectra corresponded purely to the ZnO:Ga scintillating phase and emission of polystyrene at 300-350 nm was absent. These features suggest the presence of non-radiative energy transfer from polystyrene host towards the ZnO:Ga scintillating phase which is confirmed by the measurement of X-ray excited scintillation decay with picosecond time resolution. It shows an ultrafast rise time below the time resolution of the experiment (18 ps) and a single-exponential decay with the decay time around 500 ps.

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Exposure to nerve agents, in military conflicts or terrorist acts, requires efficient decontamination systems. CeO2 nanoparticles appear efficient against organophosphorus compounds, thus we performed a benchmark on the available synthesis routes.