Energy deposition in liquid scintillators composed of CsPbBr3 colloidal nanocrystal dispersions.

Liquid scintillation processes are commonly used for various applications involving radioactivity levels analysis, as well as experiments in the field of high energy physics, most commonly in the form of organic scintillating cocktails. In this paper, we explore the potential of halide perovskite nanocrystal colloidal dispersions as an alternative to those organic mixtures. After an optimization of the nanocrystals' mean size and surface chemistry, the scintillation yield of these composite mixtures is evaluated through Compton - Triple to Double Coincidence Ratio experiments and compared with commercial liquid scintillator. The obtained results shine a light on the energy deposition mechanisms in nanocrystals-based liquid scintillators.

X-ray Scintillation in Lead Halide Perovskite Crystals.

Current technologies for X-ray detection rely on scintillation from expensive inorganic crystals grown at high-temperature, which so far has hindered the development of large-area scintillator arrays. Thanks to the presence of heavy atoms, solution-grown hybrid lead halide perovskite single crystals exhibit short X-ray absorption length and excellent detection efficiency. Here we compare X-ray scintillator characteristics of three-dimensional (3D) MAPbI3 and MAPbBr3 and two-dimensional (2D) (EDBE)PbCl4 hybrid perovskite crystals. X-ray excited thermoluminescence measurements indicate the absence of deep traps and a very small density of shallow trap states, which lessens after-glow effects. All perovskite single crystals exhibit high X-ray excited luminescence yields of >120,000 photons/MeV at low temperature. Although thermal quenching is significant at room temperature, the large exciton binding energy of 2D (EDBE)PbCl4 significantly reduces thermal effects compared to 3D perovskites, and moderate light yield of 9,000 photons/MeV can be achieved even at room temperature. This highlights the potential of 2D metal halide perovskites for large-area and low-cost scintillator devices for medical, security and scientific applications.

Spontaneous emission inhibition of telecom-band quantum disks inside single nanowire on different substrates.

We investigate the inhibited spontaneous emission of telecom-band InAs quantum disks (Qdisks) in InP nanowires (NWs). We have evaluated how the inhibition is affected by different disk diameter and thickness. We also compared the inhibition in standing InP NWs and those NWs laying on silica (SiO(2)), and silicon (Si) substrates. We found that the inhibition is altered when we put the NW on the high-refractive-index materials of Si. Experimentally, the inhibition factor ζ of the Qdisk emission at 1,500 nm decreases from 4.6 to 2.5 for NW on SiO(2) and Si substrates, respectively. Those inhibitions are even much smaller than that of 6.4 of the standing NW. The inhibition factors well agree with those calculated from the coupling of the Qdisk to the fundamental guided mode and the continuum of radiative modes. Our observation can be useful for the integration of the NW as light sources in the photonic nanodevices.

Observation of spatial fluctuations of the local density of states in random photonic media.

We experimentally study spatial fluctuations of the local density of states (LDOS) inside three-dimensional random photonic media. The LDOS is probed at many positions inside random photonic media by measuring emission rates of a large number of individual fluorescent nanospheres. The emission rates are observed to fluctuate spatially, and the variance of the fluctuations increases with the scattering strength. The measured variance of the emission rates agrees well with a model that takes into account the effect of the nearest scatterer only.

Scintillation properties and anomalous Ce(3+) emission of Cs(2)NaREBr(6):Ce(3+) (RE = La,Y,Lu).

We report the optical and scintillation properties of the Ce(3+)-doped bromoelpasolites Cs(2)NaREBr(6) (RE = La,Y,Lu). The γ-ray scintillation light yield of these materials varies from 6000 to 17 000 photons per MeV absorbed γ-ray energy. At room temperature (RT), the γ-ray scintillation decay curves for all compounds show a fast component of 61 ns, whereas the intrinsic Ce(3+) decay time is 30 ns. The scintillation mechanism in elpasolites is addressed. In Cs(2)NaLuBr(6):Ce(3+) and Cs(2)NaYBr(6):Ce(3+), we observe for the first time the so-called Ce(3+) anomalous emission in bromide compounds. This emission previously observed for chloride compounds is an ultrafast Ce(3+) emission with a selective excitation mechanism. The decay time of the anomalous emission at 10 K in bromide compounds (∼7.80 ns) is faster than that in chloride compounds (∼9.90 ns). Two bands of the anomalous emission are resolved for the first time. The mechanism behind this emission is discussed.