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The digital transformation of education is greatly accelerating in various computer-supported applications. As a particularly prominent application of the human-machine interactive system, intelligent learning systems aim to capture users' current intentions and provide recommendations through real-time feedback. However, we have a limited understanding on what is the reality of user feedback for computer-supported adaptive quizzing. This present study proposes formalization for user feedback including engagement and interactions to understand and improve intelligent adaptive quizzing. This work starts by taking individual system's action transition patterns as a temporally evolving action graph and derives patterns in terms of informing future user engagement. Furthermore, considering the student knowledge preference for a certain moment is closely related to personal experience of past learning,a novel framework EICQ (Engagement and Interaction-based Computer-Supported Adaptive Quizzing) is proposed for learning and adapting to students' current preference based on engagement trends and interaction by collecting feedback data in real-time during a learning session. This established framework captures question characters, student dynamic interactions and engagement trends, which yield a better learning experience with adaptive practice question (PQ) recommendations. Finally, much more endeavors have been made to integrate the proposed EICQ into XXXU intelligent learning systems that are co-developed with the YYY Company. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Solvents in stock solution significantly affect fluorescence properties in films. • Fluorescence quantum yield of DXP in films can be enhanced by using mixed solvent. • Photostability of DXP in films can be enhanced by using mixed solvent. • The optimal ratio of mixed solvent is 2:1 for methanol:toluene. Abstract Photostability in solid state is one of the crucial parameters of fluorescent substances for their applications. Different factors during the fabrication processes can significantly affect their photostability. In this work, we prepared N,N′-Bis(2,6-dimethylphen-yl)-perylene-3,4,9,10-tetra-carboxy-licdiimide (DXP) films by directly spin-casting the precursor solutions of DXP in a mixed solvent (methanol and toluene). We found that the photostability and fluorescence quantum yield of DXP in the final solid films have strong correlation with the ratio between methanol and toluene in the precursor solutions. These results show the importance of the solvent used during the fabrication process and give suggestions for better routes. [ABSTRACT FROM AUTHOR]

Organometal halide perovskites have attracted broad interest over the last several years for their promising applications in solar cells and light-emitting devices. It is believed that crystal defects play important roles in the photophysical processes. However, the detailed mechanism is still unclear. In this work, by using luminescence microscopy, we characterized the quenching defects correlating with crystal size, location and morphology. It is clear that needle-shaped crystals own better crystal quality with less defects; and more defects are located in the center of the crystals comparing to the edge. Relatively higher concentration of PbI 2 precursor will generate more defects during the preparation. Characterization of defects is the first step to understand the quenching mechanism and to fully understand the photophysical properties of organometal halide perovskite. [ABSTRACT FROM AUTHOR]

Cesium lead halide perovskite (CsPbX 3) nanocrystals (NCs) have exhibited promising applications in light-emitting diodes (LEDs) due to their tunable bandgap and high quantum efficiency. Backlighting LEDs based on CsPbBr 3 NCs with green emission have been widely designed to show their superiority. However, unlike CsPbBr 3 NCs, backlighting LEDs composed of mixed-halide perovskite (CsPbBr x I 3-x) NCs have rarely been reported and should be further applied in colorful LEDs for granted, mainly because of the unexpected destructive effects from the commercial polymer matrix verified in this work. Purification of a commercial polymer matrix was promoted as an effective method to eliminate the destructive effects. Further investigation proved that the species with strong polarity and oxidability, e.g., BPO in commercial PMMA, are responsible for such destructive effects by inducing the structural transformation of CsPbBr x I 3-x NCs. We believe such results can help to gain a deeper understanding of the degradation mechanism of mixed-halide perovskite materials and indicate a promising method to develop stable colorful perovskite-based LEDs. • Commercial polymer matrix have unexpected destructive effects on CsPbBr x I 3-x NCs. • Destructive effects were from the synergistic effect between polar species in commercial polymer matrix and CsPbBr x I 3-x NCs. • Purification of the commercial polymer matrix can be an effective method to eliminate the destructive effects. • CsPbBr x I 3-x NCs embedded in purified PMMA can exhibit superior stability in both solution and film. [ABSTRACT FROM AUTHOR]

Solution-processed organometal halide perovskites (OMHPs) have been widely used in optoelectronic devices, and have exhibited brilliant performance. One of their generally recognized advantages is their easy fabrication procedure. However, such a procedure also brings uncertainty about the opto-electric properties of the final samples and devices, including morphology, stability, coverage ratio, and defect concentration. Normally, one needs to find a balanced condition, because there is a competitive relation between these parameters. In this work, we fabricated CH3NH3PbI3 films by carefully changing the ratio of the PbI2 to CH3NH3I, and found that the stoichiometric and solvent engineering not only determined the photoluminescence efficiency and defects in the materials, but also affected the photostability, morphology, and coverage ratio. Combining solvent engineering and the substitution of PbI2 by Pb(Ac)2, we obtained an optimized fabrication condition, providing uniform CH3NH3PbI3 films with both high photoluminescence efficiency and high photostability under either I-rich or Pb-rich conditions. These results provide an optimized fabrication procedure for CH3NH3PbI3 and other OMHP films, which is crucial for the performance of perovskite-based solar cells and light emitting devices. [ABSTRACT FROM AUTHOR]

2D perovskite materials have attracted increasing attention in the last few years due to their optical tunability. However, how to control the structure of these materials is still one of the key challenges. In this work, by using photoluminescence microscopy and XRD characterization, we found that ethanol treatment can induce the reorganization of the crystal structure of 2D perovskite materials. The ethanol molecules can insert into (OA) 2 (MA)Pb 2 I 7 (OA = CH 3 (CH 2) 7 NH 3 ; MA = CH 3 NH 3) crystal lattice and preferentially dissolve MA ions reducing the MA/OA ratio. During the recrystallization, new (OA) 2 PbI 4 phase forms due to the low MA/OA ratio. On the other hand, adsorption of ethanol can induce the photoluminescence (PL) enhancement by passivation of the surface defects. Consequently, PL intensity increases and decreases as the activation/deactivation of the quenching defects. These results provide a possible way to optimize the crystal structure of 2D perovskite under mild condition. • Ethanol treatment can induce phase transformation of 2D perovskite from (OA) 2 (MA)Pb 2 I 7 to (OA) 2 PbI 4. • The phase transformation is caused by a dissolving-recrystallization process. • Larger crystals were obtained by the recrystallization process. • Adsorption of ethanol molecules on the surface can cause PL enhancement due to passivation of the quenching defects. [ABSTRACT FROM AUTHOR]

One of the unique characteristics of semiconductors is the strong dependence of their properties on crystal defects and doping. However, due to the species diversity and low density, it is very difficult to control the type and concentration of the defects. In perovskite materials, crystal defects are randomly formed during the fast crystallization process, causing large heterogeneity of the samples. Here, in this work, we report a controllable method to introduce surface defects on CH3NH3PbI3 perovskite materials via the interaction with 1,4-benzoquinone (BQ) molecules on the gas and solid interface. After the adsorption of BQ molecules on the perovskite surface, surface defects can be generated by photoinduced chemical reactions. The concentration of the defects can thus be controlled by precisely regulating the laser irradiation time. The concentration of the defects can be characterized by a gradually decreased PL intensity and lifetime and was found to influence the atmospheric response and the subsequent acetone-induced degradation of the materials. These results demonstrate that crystal defects in perovskite materials can be controllably introduced, which provides a possible way to fully understand the correlation between the nature and chemical structure of these defects. [ABSTRACT FROM AUTHOR]

Background: Ligand-binding proteins play key roles in many biological processes. Identification of protein-ligand binding residues is important in understanding the biological functions of proteins. Existing computational methods can be roughly categorized as sequence-based or 3D-structure-based methods. All these methods are based on traditional machine learning. In a series of binding residue prediction tasks, 3D-structure-based methods are widely superior to sequence-based methods. However, due to the great number of proteins with known amino acid sequences, sequence-based methods have considerable room for improvement with the development of deep learning. Therefore, prediction of protein-ligand binding residues with deep learning requires study. Results: In this study, we propose a new sequence-based approach called DeepCSeqSite for ab initio protein-ligand binding residue prediction. DeepCSeqSite includes a standard edition and an enhanced edition. The classifier of DeepCSeqSite is based on a deep convolutional neural network. Several convolutional layers are stacked on top of each other to extract hierarchical features. The size of the effective context scope is expanded as the number of convolutional layers increases. The long-distance dependencies between residues can be captured by the large effective context scope, and stacking several layers enables the maximum length of dependencies to be precisely controlled. The extracted features are ultimately combined through one-by-one convolution kernels and softmax to predict whether the residues are binding residues. The state-of-the-art ligand-binding method COACH and some of its submethods are selected as baselines. The methods are tested on a set of 151 nonredundant proteins and three extended test sets. Experiments show that the improvement of the Matthews correlation coefficient (MCC) is no less than 0.05. In addition, a training data augmentation method that slightly improves the performance is discussed in this study. Conclusions: Without using any templates that include 3D-structure data, DeepCSeqSite significantlyoutperforms existing sequence-based and 3D-structure-based methods, including COACH. Augmentation of the training sets slightly improves the performance. The model, code and datasets are available at https://github.com/yfCuiFaith/DeepCSeqSite. [ABSTRACT FROM AUTHOR]

To manipulate the electrical and optical properties of 2D materials via engineering their phases and crystallinity is of great significance for the construction of nanodevices with versatile functions. Herein, the controllable transformation of semimetallic gray arsenene nanoflakes into semiconducting vitreous arsenene nanoflakes via a wet chemistry vitrification method is reported. Experimental studies and theoretical simulations reveal that the vitrification of gray arsenene nanoflakes is attributed to the consumption of arsenic atoms by aqueous HF via the trigger of dissolved oxygen, resulting in a significant variation of band structure rendered by the formation of atomic structure disorderliness and arsenic atom defects/vacancies. Unlike the semimetallic features of pristine gray arsenene nanoflakes, the as‐prepared vitreous arsenene nanoflakes exhibit a strong photoluminescence peak centered at 635 nm corresponding to an optical band gap of 1.95 eV, and the field‐effect transistors based on vitreous arsenene nanoflakes also exhibit definitely p‐type semiconducting characteristics with a carrier mobility of ≈159.1 cm2 V−1 s−1. The wet chemistry induced vitrification of gray arsenene nanoflakes presents an efficient strategy to regulate the electrical and optical properties of arsenene nanoflakes, providing new insights for the interface and band structure engineering of 2D nanomaterials. [ABSTRACT FROM AUTHOR]

Hybrid organic-inorganic halide perovskite solar cells (PSCs) have achieved intriguingly high photoelectric conversion efficiencies (PCEs), but their operational stability is still not satisfactory owing to their vulnerability to moisture and heat. Herein, we report the introduction of pseudohalide thiocyanate ions and potassium dopants into formamidinium lead triiodide (FAPbI 3) to obtain a new class of pseudohalide-substituted lead halide perovskites FAPb(SCN) 2 I that can be prepared in ambient air and exhibit broad-range light absorption. Through the introduction of K+-cation doping, hole-conductor-free PSCs based on a FA 0.98 K 0.02 Pb(SCN) 2 I perovskite light absorber and a low-cost, screen-printable carbon-based counter electrode exhibited a PCE of 13.39%. Importantly, the FA 0.98 K 0.02 Pb(SCN) 2 I-based hole-conductor-free PSCs exhibited an 88% PCE retention even after continuous heating at 100 °C for 1020 h, indicating excellent thermal stability. This study suggests that the compositional engineering of non-iodine X-site pseudohalide anion substitution and A-site cation doping hold great promise for improving the stability of PSCs. [ABSTRACT FROM AUTHOR]