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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]

Throughout years, the two-step spin-coating process is the most common method to prepare organic lead halide perovskite materials. However, the short reaction time of dropping the solution at the second step means that PbI2 cannot be completely transformed into perovskite phase. To solve this problem, we report the introduction of glycine hydrochloride (GlyHCl) into the second step of the two-step spin-coating process to prepare a FA0.9MA0.1PbI3-x%-GlyHCl perovskite material (namely FAMA-x%-GlyHCl, where FA = formamidinium, MA = methylammonium, and x% stands for the molar ratio of GlyHCl added in FA iodide/MA iodide (FAI/MAI) precursor solution). The Cl− ion in GlyHCl assists the formation of α-phase perovskite, and the −COO− group coordinates with Pb2+ cation in a bridging way, making up for the anion vacancy in perovskite lattice and resulting in high absorption intensity. The perovskite solar cells (PSCs) based on FAMA-9%-GlyHCl achieve a long carrier lifetime (527.0 ns), a photoelectric conversion efficiency (PCE) of 19.40% and good thermal stability, maintaining 85.8% of the initial PCE after being continuously heated at 60 °C for 500 h. This study helps to solve the problem of incomplete reaction in the two-step spin-coating process and puts forward a new solution for preparing high coverage perovskite films with large grain size. [ABSTRACT FROM AUTHOR]

Metal–halide perovskite nanocrystals (NCs) have gained significant attention in the field of optoelectronic and photonic devices due to their promising applications. Despite their exceptional optical properties, the impact of different synthetic strategies on the fundamental nature of NCs, such as nonradiative recombination centers, remains poorly understood. In this study, we investigated the photophysical properties of CsPbBr3 NCs synthesized using two distinct methods, hot injection and ligand-assisted reprecipitation, at the individual particle level. We observed different blinking behaviors under specific photoexcitation power densities and proposed, through intensity–lifetime analysis and Monte–Carlo simulations, that these different synthetic strategies can fabricate NCs with similar crystal structures but distinct surface quenchers with varying energy levels, which significantly affected the photo-induced blinking-down and blinking-up behaviors in individual NCs. Our findings indicate a practical and feasible approach for controlling defect engineering in perovskite NCs, with significant implications for their use in optoelectronic and other technological applications. [ABSTRACT FROM AUTHOR]

All-inorganic perovskites, adopting cesium (Cs+) cation to completely replace the organic component of A-sites of hybrid organic–inorganic halide perovskites, have attracted much attention owing to the excellent thermal stability. However, all-inorganic iodine-based perovskites generally exhibit poor phase stability in ambient conditions. Herein, we propose an efficient strategy to introduce antimony (Sb3+) into the crystalline lattices of CsPbI2Br perovskite, which can effectively regulate the growth of perovskite crystals to obtain a more stable perovskite phase. Due to the much smaller ionic radius and lower electronegativity of trivalent Sb3+ than those of Pb2+, the Sb3+ doping can decrease surface defects and suppress charge recombination, resulting in longer carrier lifetime and negligible hysteresis. As a result, the all-inorganic perovskite solar cells (PSCs) based on 0.25% Sb3+ doped CsPbI2Br light absorber and screen-printable nanocarbon counter electrode achieved a power conversion efficiency of 11.06%, which is 16% higher than that of the control devices without Sb3+ doping. Moreover, the Sb3+ doped all-inorganic PSCs also exhibited greatly improved endurance against heat and moisture. Due to the use of low-cost and easy-to-process nanocarbon counter electrodes, the manufacturing process of the all-inorganic PSCs is very convenient and highly repeatable, and the manufacturing cost can be greatly reduced. This work offers a promising approach to constructing high-stability all-inorganic PSCs by introducing appropriate lattice doping. [ABSTRACT FROM AUTHOR]

Organic-inorganic metal halide perovskites have attained extensive attention owing to their outstanding photovoltaic performances, but the existence of numerous defects in crystalline perovskites is still a serious constraint for the further development of perovskite solar cells (PSCs). In particular, the rapid crystallization guided by anti-solvents leads to plenty of surficial and interfacial defects in perovskite films. Herein, we report the adoption of a pseudo-halide anion based ionic liquid additive, 1-butyl-3-methylimidazolium thiocyanate (BMIMSCN) for growing ternary cation (CsFAMA, where FA = formamidinium and MA = methylammonium) perovskites with large-scale crystal grains and strong preferential orientation via the enhanced Ostwald ripening. Meanwhile, a novel halide-free passivator, benzylammonium formate (BAFa), was employed as a buffering layer on the perovskite films to suppress surface-dominated charge recombination. As a result, the cooperative effects of BMIMSCN additive and BAFa passivator lead to significant enhancements on fluorescence lifetime (from 79.41 to 201.01 ns), open-circuit voltage (from 1.13 to 1.19 V), and photoelectric conversion efficiency (from 18.90% to 22.33%). Moreover, the BMIMSCN/BAFa-CsFAMA PSCs demonstrated greatly improved stability against moisture and heat. This work suggests a promising strategy to improve the quality of perovskite materials via reducing the surficial and interfacial defects by the synergistic effects of lattice doping and interface engineering. [ABSTRACT FROM AUTHOR]

Sensitive detection of local acoustic vibrations at the nanometer scale has promising potential applications involving miniaturized devices in many areas, such as geological exploration, military reconnaissance, and ultrasound imaging. However, sensitive detection of weak acoustic signals with high spatial resolution at room temperature has become a major challenge. Here, we report a nanometer-scale system for acoustic detection with a single molecule as a probe based on minute variations of its distance to the surface of a plasmonic gold nanorod. This system can extract the frequency and amplitude of acoustic vibrations with experimental and theoretical sensitivities of 10 pm Hz−1/2 and 10 fm Hz−1/2, respectively. This approach provides a strategy for the optical detection of acoustic waves based on molecular spectroscopy without electromagnetic interference. Moreover, such a small nano-acoustic detector with 40-nm size can be employed to monitor acoustic vibrations or read out the quantum states of nanomechanical devices. .Sensitive detection of weak acoustic signals at nanometer scale is challenging. Here, the authors present an acoustic detection system based on a single molecule as a probe, where frequency and amplitude of acoustic vibrations can be extracted from its minute variations in distance to the surface of a plasmonic gold nanorod. [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]

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]

As the first step of machine-learning based protein structure and function prediction, the amino acid encoding play a fundamental role in the final success of those methods. Different from the protein sequence encoding, the amino acid encoding can be used in both residue-level and sequence-level prediction of protein properties by combining them with different algorithms. However, it has not attracted enough attention in the past decades, and there are no comprehensive reviews and assessments about encoding methods so far. In this article, we make a systematic classification and propose a comprehensive review and assessment for various amino acid encoding methods. Those methods are grouped into five categories according to their information sources and information extraction methodologies, including binary encoding, physicochemical properties encoding, evolution-based encoding, structure-based encoding, and machine-learning encoding. Then, 16 representative methods from five categories are selected and compared on protein secondary structure prediction and protein fold recognition tasks by using large-scale benchmark datasets. The results show that the evolution-based position-dependent encoding method PSSM achieved the best performance, and the structure-based and machine-learning encoding methods also show some potential for further application, the neural network based distributed representation of amino acids in particular may bring new light to this area. We hope that the review and assessment are useful for future studies in amino acid encoding. [ABSTRACT FROM AUTHOR]

Inorganic perovskite materials have attracted broad interest in the last several years due to their stability and promising applications as photovoltaic and light‐emitting materials. In this work, we prepared Cs4PbBr6 nanoparticles showing stable photoluminescence (PL) without blinking and studied the PL properties of individual Cs4PbBr6 nanoparticles in the biological temperature range. We found that both PL intensity and lifetime of a single Cs4PbBr6 particle strongly depends on the temperature. The PL intensity and lifetime decrease almost linearly with the increasing of the temperature. The slopes of the PL intensity and lifetime versus temperature were as high as 2% and 3% per degree centigrade, respectively. The photostability and thermal stability were also checked for individual particles. With these results, we proposed that the sensitivity of PL intensity and lifetime of a single Cs4PbBr6 nanoparticle on temperature showed the potential application of a single particle as a nanothermometer for thermal detection in a local environment. Take the temperature: Non‐blinking Cs4PbBr6 nanoparticles show potential as a single‐particle thermometers to detect local temperatures on the nanometer scale. [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]

Post-fabrication defect passivation of organometal halide perovskites has become an efficient way to improve their photophysical properties, but the underlying mechanisms are still in debate. In this work, we used p-benzoquinone (p-BQ) to generate surface defects on methylammonium lead triiodide perovskite (MAPbI3), and found that a Usanovich acid–base (O2, acetone or acetonitrile) treatment can effectively passivate those defects and lead to photoluminescence (PL) enhancement. The passivation effect arose from partial neutralization of defect charges via electron transfer between passivation reagents and relevant defects. O2 accepted photo-generated electrons, formed negatively charged oxygen species and attached to the I vacancy site to reduce its PL quenching efficiency by neutralising the defects positive charge. Likewise, acetone accepted photo-generated holes, formed positively charged species and partially neutralised the defects negative charge. The reduced trapping ability of defects caused PL enhancement. In addition, the observed photo-catalysed oxidation of acetone by O2 on the crystal surface supported the single electron transfer mechanism, and showed the potential of MAPbI3 as a photo-catalyst. [ABSTRACT FROM AUTHOR]

The joint computational and experimental efforts reveal that the organic molecule 1,2-diisocyano-4,5-dimethylbenzene (1) acts as both a reactant and a photosensitizer (PS) in a metal-free reaction with perfluoroalkylhalide (2) to produce 2-perfluoroalkyl quinoxalines (3) under visible light. Both the π–π stacking aggregation in crystals and the solvation in various solvents of PS 1 exhibited visible-light absorption at 466 nm in spite of its smaller coefficient than that of the ultraviolet-light absorption. Such an aggregation-assisted visible-light absorption phenomenon is rationalized by theoretical calculations of the condensed-phase properties with the consideration of the explicit polarization effect from the neighboring molecules. Upon irradiation with different wavelengths, the emission colors changed from navy to bright yellow. Fluorescence lifetime measurements show that the emission of 1 comes from its singlet excited state. The aggregation induced emission when excited at 420 nm has a shorter lifetime (0.45 ns) than that of the emission from isolated molecules (2.71 ns) when excited at 381 nm. It is conceived that the aggregation assisted visible light absorption properties may be general in other photo-reactive molecules, such as 1,4-diisocyano-2,5-dimethylbenzene (4), 1,4-dicyanobenzene (5), and 1,4-diisocyanobenzene (6), which are widely used in many photochemical reactions in the absence of any external photosensitizer. [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]