Fe3O4–graphene composites with three‐dimensional laminated structures have been synthesised by a simple in situ hydrothermal method. From field‐emission and transmission electron microscopy results, ...the Fe3O4 nanoparticles, around 3–15 nm in size, are highly encapsulated in a graphene nanosheet matrix. The reversible Li‐cycling properties of Fe3O4–graphene have been evaluated by galvanostatic discharge–charge cycling, cyclic voltammetry and impedance spectroscopy. Results show that the Fe3O4–graphene nanocomposite with a graphene content of 38.0 wt % exhibits a stable capacity of about 650 mAh g−1 with no noticeable fading for up to 100 cycles in the voltage range of 0.0–3.0 V. The superior performance of Fe3O4–graphene is clearly established by comparison of the results with those from bare Fe3O4. The graphene nanosheets in the composite materials could act not only as lithium storage active materials, but also as an electronically conductive matrix to improve the electrochemical performance of Fe3O4.
That's a wrap! A Fe3O4–graphene nanosheet composite with a 3D laminated structure has been synthesised through a simple hydrothermal method. The as‐prepared Fe3O4–graphene nanosheet composite (see figure) exhibits superior cycling behaviour, retaining a capacity above 650 mAh g−1 beyond 100 cycles.
In this review, the factors influencing the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is emphasized. The PCE of PSCs has remarkably increased from 3.8% to 23.7%, but on the ...other hand, poor stability is one of the main facets that creates a huge barrier in the commercialization of PSCs. Herein, a concise overview of the current efforts to enhance the stability of PSCs is provided; moreover, the degradation causes and mechanisms are summarized. The strategies to improve device stability are portrayed in terms of structural effects, a photoactive layer, hole‐ and electron‐transporting layers, electrode materials, and device encapsulation. Last but not least, the economic feasibility of PSCs is also vividly discussed.
In parallel with the tremendous progress in the efficiency of perovskite solar cells, research on the issue of instability has attracted enormous attention. In this review, the strategies to enhance the stability from the perspectives of the device structure, the photoactive layer, hole‐ and electron‐transporting layers, electrode materials, and device encapsulation are portrayed.
Low light often leads to poor image visibility, which can easily affect the performance of computer vision algorithms. First, this paper proposes the absorption light scattering model (ALSM), which ...can be used to reasonably explain the absorbed light imaging process for low-light images. In addition, the absorbing light scattering image obtained via ALSM under a sufficient and uniform illumination can reproduce hidden outlines and details from the low-light image. Then, we identify that the minimum channel of ALSM obtained above exhibits high local similarity. This similarity can be constrained by superpixels, which effectively prevent the use of gradient operations at the edges so that the noise is not amplified quickly during enhancement. Finally, by analyzing the monotonicity between the scene reflection and the atmospheric light or transmittance in ALSM, a new low-light image enhancement method is identified. We replace atmospheric light with inverted atmospheric light to reduce the contribution of atmospheric light in the imaging results. Moreover, a soft jointed mean-standard-deviation (MSD) mechanism is proposed that directly acts on the patches represented by the superpixels. The MSD can obtain a smaller transmittance than that obtained by the minimum strategy, and it can be automatically adjusted according to the information of the image. The experiments on challenging low-light images are conducted to reveal the advantages of our method compared with other powerful techniques.
Surface trap-mediated nonradiative charge recombination is a major limit to achieving high-efficiency metal-halide perovskite photovoltaics. The ionic character of perovskite lattice has enabled ...molecular defect passivation approaches through interaction between functional groups and defects. However, a lack of in-depth understanding of how the molecular configuration influences the passivation effectiveness is a challenge to rational molecule design. Here, the chemical environment of a functional group that is activated for defect passivation was systematically investigated with theophylline, caffeine, and theobromine. When N-H and C=O were in an optimal configuration in the molecule, hydrogen-bond formation between N-H and I (iodine) assisted the primary C=O binding with the antisite Pb (lead) defect to maximize surface-defect binding. A stabilized power conversion efficiency of 22.6% of photovoltaic device was demonstrated with theophylline treatment.
Since the emergence of inorganic–organic hybrid perovskites a few years ago, there have been many promising achievements in the field of green and red perovskite light‐emitting diodes (PeLEDs). ...Nevertheless, the performance of blue‐light PeLEDs faces challenges. In this work, the unique synergy obtained by introducing two different ligands to successfully form quasi‐2D perovskite films, which can exhibit stable blue‐light emission, is utilized. The fabricated PeLEDs have a maximum external quantum efficiency of 2.62% and a half lifetime (T50) of 8.8 min. Meanwhile, the electroluminescence spectrum with its peak located at 485 nm, demonstrates improved stability by applying different voltage bias. The finding in this work offers a new way to achieve steady blue PeLEDs with high performance.
Utilizing synergistic effects with two different ligands, a stable blue perovskite emitter is successfully fabricated. The corresponding blue perovskite light‐emitting diode shows excellent device performance with a peak external quantum efficiency of 2.62% and a T50 lifetime of 8.8 min, demonstrating remarkable color stability under operation.
Atomically precise enantiomeric metal clusters are scarce, and copper(I) alkynyl clusters with intense circularly polarized luminescence (CPL) responses have not been reported. A pair of chiral ...alkynyl ligands, (R/S)‐2‐diphenyl‐2‐hydroxylmethylpyrrolidine‐1‐propyne (abbreviated as R/S‐DPM) we successfully prepared and single crystals were characterized of optically pure enantiomeric pair of atomically‐precise copper(I) clusters, Cu14(R/S‐DPM)8(PF6)6 (denoted as R/S‐Cu14), which feature bright red luminescence and CPL with a high luminescence anisotropy factor (glum). A dilute solution containing R/S‐Cu14 was nonluminescent and CPL inactive at room temperature. Crystallization‐ and aggregation‐induced emission (CIE and AIE, respectively) contribute to the triggering of the CPL of R/S‐Cu14 in the crystalline and aggregated states. Their AIE behavior and good biocompatibility indicated applications of these copper(I) clusters in cell imaging in HeLa and NG108‐15 cells.
Atomically precise chiral CuI alkynyl nanoclusters R/S‐Cu14 with inherent chirality were synthesized for the first time. Crystallization‐ and aggregation‐induced emission (CIE and AIE, respectively) trigger circularly polarized luminescence (CPL) with an unprecedented luminescence anisotropy factor (glum).
Atomically precise copper clusters are highly desirable catalysts for electrocatalytic CO2 reduction reaction (CO2RR) and provide an ideal platform for elaborating structure–activity relationships. ...However, systematic comparative studies of Cu cluster isomers for electrocatalytic CO2RR are lacking because they are challenging to synthesize. A group of structurally precise Cu8 cluster isomers with different core structures (cube‐ and ditetrahedron‐shaped) were developed and investigated for highly active and selective CO2 reduction. Electrocatalytic measurements showed that the ditetrahedron‐shaped Cu8 cluster exhibited a higher FEHCOOH (≈92 %) at −1.0 V and higher selectivity than the cube‐shaped cluster. Theoretical investigations revealed different levels of competitiveness with the hydrogen evolution reaction on the respective core‐shaped Cu8 clusters and decreased free energies for the adsorbed HCOO* intermediates on the ditetrahedron‐shaped Cu8 clusters.
A group of atomically precise Cu8 cluster isomers with two core structures (cube‐ and ditetrahedron‐shaped) were investigated for highly active and selective CO2 reduction. A difference in catalytic performance was attributed to variable metal core arrangements hidden in Cu8 nanoclusters. The ditetrahedron‐shaped cluster exhibits a high Faradaic efficiency for formic acid generation (FEHCOOH) almost two times that of the cube‐shaped cluster.
Alloying is an efficient chemistry to tailor the properties of metal clusters. As a class of promising radiosensitizers, most previously reported metal clusters exhibit unitary function and cannot ...overcome radioresistance of hypoxic tumors. Here, atomically precise alloy clusters Pt2M4 (M = Au, Ag, Cu) are synthesized with bright luminescence and adequate biocompatibility, and their composition‐dependent enzyme mimicking activity and radiosensitizing effect is explored. Specifically, only the Pt2Au4 cluster displays catalase‐like activity, while the others do not have clusterzyme properties, and its radiosensitizing effect is the highest among all the alloy clusters tested. By taking advantage of the sustainable production of O2 via the decomposition of endogenous H2O2, the Pt2Au4 cluster modulates tumor hypoxia as well as increases the efficacy of radiotherapy. This work thus advances the cluster alloying strategy to produce multifunctional therapeutic agents for improving hypoxic tumor therapy.
Atomically precise alloy clusters Pt2M4 (M = Au, Ag, Cu) are synthesized with bright luminescence and adequate biocompatibility. The experimental results reveal that the Pt2Au4 cluster displays catalase‐like activity and its radiosensitizing effect is the highest. By taking advantage of the sustainable production of O2 via decomposition of endogenous H2O2, the Pt2Au4 cluster modulates tumor hypoxia as well as increases the efficacy of radiotherapy.
Multiple-instance active learning (MIAL) is a paradigm to collect sufficient training bags for a multiple-instance learning (MIL) problem, by selecting and querying the most valuable unlabeled bags ...iteratively. Existing works on MIAL evaluate an unlabeled bag by its informativeness with regard to the current classifier, but neglect the internal distribution of its instances, which can reflect the diversity of the bag. In this paper, two diversity criteria, i.e., clustering-based diversity and fuzzy rough set based diversity, are proposed for MIAL by utilizing a support vector machine (SVM) based MIL classifier. In the first criterion, a kernel k-means clustering algorithm is used to explore the hidden structure of the instances in the feature space of the SVM, and the diversity degree of an unlabeled bag is measured by the number of unique clusters covered by the bag. In the second criterion, the lower approximations in fuzzy rough sets are used to define a new concept named dissimilarity degree, which depicts the uniqueness of an instance so as to measure the diversity degree of a bag. By incorporating the proposed diversity criteria with existing informativeness measurements, new MIAL algorithms are developed, which can select bags with both high informativeness and diversity. Experimental comparisons demonstrate the feasibility and effectiveness of the proposed methods.
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