Role of Excess FAI in Formation of High‐Efficiency FAPbI3‐Based Light‐Emitting Diodes

Introducing extensively excess ammonium halides when forming perovskites has recently been demonstrated as an effective approach to improve the performance of perovskite light‐emitting diodes (PeLEDs). Here, Cs_0.17FA_0.83PbI_2.5Br_0.5 is used as a model system to elucidate the impact of introducing excess formamidinium iodide (FAI) on the crystallization process of the perovskite film and operation of the corresponding PeLED. The excess FAI ratio is varied from 0 to 120 mol% and the crystallization process of the perovskite through in situ absorbance, in situ photoluminescence, and ex situ X‐ray diffraction measurements is systematically monitored. The results suggest that excess FAI triggers formation of a compact wide‐bandgap intermediate phase in the as‐deposited film, which then transforms to isolated and highly crystalline perovskite grains upon annealing. Using excitation correlation photoluminescence spectroscopy it is found that excess FAI results in a lower density of deep trap states and therefore a reduction of nonradiative losses in the material. This leads to a greatly enhanced maximum external quantum efficiency (EQE) from 0.25% (stoichiometric) to 12.7% (90 mol% excess). Furthermore, the FAI‐excess perovskite film is optimized with Pb(SCN)₂ and 5‐ammonium valeric acid iodide additives and achieve a record radiance of 965 W Sr^?1 m^?2 for near‐infrared PeLEDs and a high EQE of 17.4%.     

Could hop-derived bitter compounds improve glucose homeostasis by stimulating the secretion of GLP-1?

Hops (Humulus lupulus L.) is by far the greatest contributors to the bitter property of beer. Over the past years, a large body of evidence demonstrated the presence of taste receptors in different locations of the oral cavity. In addition to the taste buds of the tongue, cells expressing these receptors have been identified in olfactory bulbs, respiratory and gastrointestinal tract. In the gut, the attention was mainly directed to sweet Taste Receptor (T1R) and bitter Taste Receptor (T2R) receptors. In particular, T2R has shown to modulate secretion of different gut hormones, mainly Glucagon-like Peptide 1 (GLP-1), which are involved in the regulation of glucose homeostasis and the control of gut motility, thereby increasing the sense of satiety. Scientific interest in the activity of bitter taste receptors emerges because of their wide distribution in the human species and the large range of natural substances that interact with them. Beer, whose alcohol content is lower than in other common alcoholic beverages, contains a considerable amount of bitter compounds and current scientific evidence shows a direct effect of beer compounds on glucose homeostasis. The purpose of this paper is to review the available literature data in order to substantiate the novel hypothesis of a possible direct effect of hop-derived bitter compounds on secretion of GLP-1, through the activation of T2R, with consequent improvement of glucose homeostasis.     

Defect Activity in Lead Halide Perovskites

The presence of various types of chemical interactions in metal‐halide perovskite semiconductors gives them a characteristic “soft” fluctuating structure, prone to a wide set of defects. Understanding of the nature of defects and their photochemistry is summarized, which leverages the cooperative action of density functional theory investigations and accurate experimental design. This knowledge is used to describe how defect activity determines the macroscopic properties of the material and related devices. Finally, a discussion of the open questions provides a path towards achieving an educated prediction of device operation, necessary to engineer reliable devices.     

Site‐Controlled Single‐Photon Emitters Fabricated by Near‐Field Illumination

Many of the most advanced applications of semiconductor quantum dots (QDs) in quantum information technology require a fine control of the QDs' position and confinement potential, which cannot be achieved with conventional growth techniques. Here, a novel and versatile approach for the fabrication of site‐controlled QDs is presented. Hydrogen incorporation in GaAsN results in the formation of N–2H and N–2H–H complexes, which neutralize all the effects of N on GaAs, including the N‐induced large reduction of the bandgap energy. Starting from a fully hydrogenated GaAs/GaAsN:H/GaAs quantum well, the N? H bonds located within the light spot generated by a scanning near‐field optical microscope tip are broken, thus obtaining site‐controlled GaAsN QDs surrounded by a barrier of GaAsN:H (laterally) and GaAs (above and below). By adjusting the laser power density and exposure time, the optical properties of the QDs can be finely controlled and optimized, tuning the quantum confinement energy over more than 100 meV and resulting in the observation of single‐photon emission from both the exciton and biexciton recombinations. This novel fabrication technique reaches a position accuracy <100 nm and it can easily be applied to the realization of more complex nanostructures.     

Prediction model for determining the optimum operational parameters in laser forming of fiber-reinforced composites

Composite materials are widely employed in various industries, such as aerospace, automobile, and sports equipment, owing to their lightweight and strong structure in comparison with conventional materials. Laser material processing is a rapid technique for performing the various processes on composite materials. In particular, laser forming is a flexible and reliable approach for shaping fiber-metal laminates (FMLs), which are widely used in the aerospace industry due to several advantages, such as high strength and light weight. In this study, a prediction model was developed for determining the optimal laser parameters (power and speed) when forming FML composites. Artificial neural networks (ANNs) were applied to estimate the process outputs (temperature and bending angle) as a result of the modeling process. For this purpose, several ANN models were developed using various strategies. Finally, the achieved results demonstrated the advantage of the models for predicting the optimal operational parameters.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00304-3     

Forecasting lava flow hazards during the 2006 Etna eruption: Using the MAGFLOW cellular automata model

The MAGFLOW cellular automata (CA) model was able to fairly accurately reproduce the time of the lava flow advance during the 2006 Etna eruption, leading to very plausible flow predictions. MAGFLOW is intended for use in emergency response situations during an eruption to quickly forecast the lava flow path over some time interval from the immediate future to a long-time forecast. Major discrepancies between the observed and simulated paths occurred in the early phase of the 2006 eruption due to an underestimation of the initial flow rate, and at the time of the overlapping with the 2004–2005 lava flow. Very good representations of the areas likely to be inundated by lava flows were obtained when we adopt a time-varying effusion rate and include the 2004–2005 lava flow field in the Digital Elevation Model (DEM) of topography.     

Decomposition of the polycyclic nitramine explosive, CL-20, by Fe(0)

CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), C6H6N12O12, is an emerging energetic chemical that may replace RDX, but its degradation pathways are not well-known. In the present study, zerovalent iron was used to degrade CL-20 with the aim of determining its products and degradation pathways. In the absence of O2, CL-20 underwent a rapid decomposition with the concurrent formation of nitrite to ultimately produce nitrous oxide, ammonium, formate, glyoxal, and glycolate. LC/MS (ES-) showed the presence of several key products carrying important information on the initial reactions involved in the degradation of CL-20. For instance, a doubly denitrated intermediate of CL-20 was detected together with the mono- and dinitroso derivatives of the energetic chemical. Two other intermediates with [M-H]- at 392 and 376 Da, matching empirical formulas of C6H7N11O10 and C6H7N11O9, respectively, were detected. Using 15N-labeled CL-20, the two intermediates were tentatively identified as the denitrohydrogenated products of CL-20 and its mononitroso derivative, respectively. The present experimental findings suggest that CL-20 degraded via at least two initial routes: one involving denitration and the second involving sequential reduction of the N-NO2 to the corresponding nitroso (N-NO) derivatives prior to denitration and ring cleavage.