纳米孔缺陷导致单层黑磷电荷局域极大抑制非辐射电子-空穴复合的时域模拟

通常认为缺陷加速黑磷的非辐射电子-空穴复合,阻碍器件性能的持续提高。实验打破了这一认识。采用含时密度泛函理论结合非绝热分子动力学,我们发现P-P伸缩振动驱动非辐射电子-空穴复合,使纳米孔修饰的单层黑磷的激发态寿命比完美体系延长了约5.5倍。这主要归因于三个因素。一,纳米孔结构不但没有在禁带中引入深能级缺陷,而且由于价带顶下移使带隙增加了0.22 eV。二,除了带隙增加,纳米孔减小了电子和空穴波函数重叠,并抑制了原子核热运动,从而使非绝热耦合降低至完美体系的约1/2。三,退相干时间比完美体系延长了1.5倍。前两个因素战胜了第三个因素,使纳米孔结构激发态寿命延长至2.74 ns,而其在完美体系中约为480 ps。我们的研究表明可以制造合理数量和形貌的缺陷,如纳米孔,降低黑磷非辐射电子-空穴复合,提高光电器件效率。这一研究对于理解和调控黑磷和其它二维材料的激发态性质有重要意义。     

Comprehensive Characterization of Shredded Lithium-Ion Battery Recycling Material

Herein we report on an analytical study of dry-shredded lithium-ion battery (LIB) materials with unknown composition. Samples from an industrial recycling process were analyzed concerning the elemental composition and (organic) compound speciation. Deep understanding of the base material for LIB recycling was obtained by identification and analysis of transition metal stoichiometry, current collector metals, base electrolyte and electrolyte additive residues, aging marker molecules and polymer binder fingerprints. For reversed engineering purposes, the main electrode and electrolyte chemistries were traced back to pristine materials. Furthermore, possible lifetime application and accompanied aging was evaluated based on target analysis on characteristic molecules described in literature. With this, the reported analytics provided precious information for value estimation of the undefined spent batteries and enabled tailored recycling process deliberations. The comprehensive feedstock characterization shown in this work paves the way for targeted process control in LIB recycling processes.     

Self-assembly in magnetic supramolecular hydrogels

Most recent advances in the synthesis of supramolecular hydrogels based on low molecular weight gelators (LMWGs) have focused on the development of novel hybrid hydrogels, combining LMWGs and different additives. The dynamic nature of the noncovalent interactions of supramolecular hydrogels, together with the specific properties of the additives included in the formulation, allow these novel hybrid hydrogels to present interesting features, such as stimuli-responsiveness, gel-sol reversibility, self-healing and thixotropy, which make them very appealing for multiple biomedical and biotechnological applications. In particular, the inclusion of magnetic nanoparticles in the hydrogel matrix results in magnetic hydrogels, a particular type of stimuli-responsive materials that respond to applied magnetic fields. This review focuses on the recent advances in the development of magnetic supramolecular hydrogels, with special emphasis in the role of the magnetic nanoparticles in the self-assembly process, as well as in the exciting applications of these materials.     

Pore Engineering for Covalent Organic Framework Membranes

Membrane technology is of particular significance for the sustainable development of society owing to its potential capacity to tackle the energy shortage and environmental pollution. Membrane materials are the core part of membrane technology. Researchers have always been pursuing predictable structures of advanced membrane materials, which provides a possibility to fully unlock the potential of membranes. Covalent organic frameworks(COFs), with the advantage of controllable pore microenvironment, are considered to be promising candidates to achieve this design concept. The customizable function of COF membranes through pore engineering does well in the enhancement of selective permeability performance, which offers COF membranes with great application potentials in separation and transportation fields. In this context, COF-based membranes have been developed rapidly in recent years. Herein, we present a brief overview on the strategies developed for pore engineering of COF membranes in recent years, including skeleton engineering, pore surface engineering, host-guest chemistry and membrane fabrication. Moreover, the features of transmission or separation of molecules/ions based on COF membranes and corresponding applications are also introduced. In the last part, the challenges and prospects of the development of COF membranes are discussed.     

Surface domain potential difference-mediated efficient charge separation on a defective ZnIn2S4 microsphere photocatalyst

Low-efficiency charge separation in metal sulfides is a major obstacle to realizing high photocatalytic performance. Herein, we propose the concept of a similar surface domain potential difference between adjacent microdomains with and without surface S vacancies on ZnIn₂S₄ to mediate charge separation. Defective ZnIn₂S₄ microspheres (DZISNPs) are prepared through a solvothermal method combined with a low-temperature hydrogenation surface engineering strategy. The as-prepared DZISNPs with a narrowed bandgap of 2.38 eV possess a large specific surface area of 178.5 m² g^?1, a pore size of 6.89 nm, and a pore volume of 0.36 cm³ g^?1, which further improves the visible light absorption. The resultant DZISNPs exhibit excellent visible light activity (2.15 mmol h^?1 g^?1), which is ～two-fold higher than that of the original DZISNP. The experimental results and DFT calculations reveal that the enhanced property can be a result of the surface S vacancy-induced surface domain potential difference, promoting the spatial separation of electrons and holes. Furthermore, the long-term stability of the DZISNPs indicates that the formation of surface S vacancies can inhibit the photocorrosion of ZnIn₂S₄. This strategy provides new insights for fabricating highly efficient and stable sulfide photocatalysts.     

Evaluation of PEGylated fibrin as a three-dimensional biodegradable scaffold for ovarian tissue engineering

The most challenging task of creating a bioengineered ovary to restore fertility in cancer patients is choosing an appropriate biomaterial to encapsulate isolated preantral follicles and ovarian cells. In this study, as a biocompatible and biodegradable biomaterial containing fibrin-like bioactivity and manageable physical properties, PEGylated fibrin aims to encapsulate isolated ovarian stromal cells as a first step of creating an engineered ovarian tissue. For this purpose, human ovarian stromal cells were isolated from frozen-thawed ovarian tissue and cultured in the PEGylated fibrin hydrogels (PEG:Fib), which were fabricated by combining two different molar ratios of PEG:Fib (10:1 and 5:1) and two thrombin concentrations. The samples were analyzed at days 0 and 5 of in vitro for cell density, proliferation (Ki67), and apoptosis (caspase-3). Moreover, LIVE/DEAD and PrestoBlue assays assessed cell viability and proliferation on days 1, 3, and 5. The effect of PEGylation on the biodegradation behavior of fibrin was evaluated by measuring the remaining mass ratio of non-modified fibrin, PEG:Fib 10:1, and PEG:Fib 5:1 hydrogels after 1, 2, 3, 5, 8, 11, and 15 days. The results showed that PEGylated fibrin hydrogels enhanced scaffold stability and supported cell viability and proliferation. In addition, PEG:Fib 5:1 T50 indicated a significantly higher cell density dynamic and non-significantly lower expression of caspase-3 on day 5. Besides, uniformity of cell distribution inside the hydrogel and a tendency to a high rate of Ki67-positive cells was observed in PEG:Fib 10:1 T50 hydrogels. In conclusion, this study reveals the positive effects of PEGylated fibrin hydrogels on isolated human ovarian stromal cells. Based on such promising findings, we believe that this matrix should be tested to encapsulate isolated human ovarian follicles.     

Defect Engineering and Anisotropic Modulation of Ionic Transport in Perovskite Solid Electrolyte LixLa(1−x)/3NbO3

Solid electrolytes, such as perovskite Li_3xLa_2/1−xTiO₃, Li_xLa_(1−x)/3NbO₃ and garnet Li₇La₃Zr₂O₁₂ ceramic oxides, have attracted extensive attention in lithium-ion battery research due to their good chemical stability and the improvability of their ionic conductivity with great potential in solid electrolyte battery applications. These solid oxides eliminate safety issues and cycling instability, which are common challenges in the current commercial lithium-ion batteries based on organic liquid electrolytes. However, in practical applications, structural disorders such as point defects and grain boundaries play a dominating role in the ionic transport of these solid electrolytes, where defect engineering to tailor or improve the ionic conductive property is still seldom reported. Here, we demonstrate a defect engineering approach to alter the ionic conductive channels in Li_xLa_(1−x)/3NbO₃ (x = 0.1~0.13) electrolytes based on the rearrangements of La sites through a quenching process. The changes in the occupancy and interstitial defects of La ions lead to anisotropic modulation of ionic conductivity with the increase in quenching temperatures. Our trial in this work on the defect engineering of quenched electrolytes will offer opportunities to optimize ionic conductivity and benefit the solid electrolyte battery applications.     

Investigation of Parameters Influencing Tubular-Shaped Chitosan-Hydroxyapatite Layer Electrodeposition

Tubular-shaped layer electrodeposition from chitosan-hydroxyapatite colloidal solutions has found application in the field of regeneration or replacement of cylindrical tissues and organs, especially peripheral nerve tissue regeneration. Nevertheless, the quantitative and qualitative characterisation of this phenomenon has not been described. In this work, the colloidal systems are subjected to the action of an electric current initiated at different voltages. Parameters of the electrodeposition process (i.e., total charge exchanged, gas volume, and deposit thickness) are monitored over time. Deposit structures are investigated by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The value of voltage influences structural characteristics but not thickness of deposit for the process lasting at least 20 min. The calculated number of exchanged electrons for studied conditions suggests that the mechanism of deposit formation is governed not only by water electrolysis but also interactions between formed hydroxide ions and calcium ions coordinated by chitosan chains.     

Room Temperature Ionic Liquids in Asymmetric Hetero-Ene Type Reactions: Improving Organocatalyst Performance at Lower Temperatures

Room temperature ionic liquids (RTILs) have been widely used as (co)solvents in several catalytic processes modifying, in most of the cases, the catalyst activity and/or the selectivity for the studied reactions. However, there are just a few examples of their use in hydrogen bonding organocatalysis. In this paper, we show the positive effect of a set of imidazole-based ionic liquids ([bmim]BF₄ and [hmim]PF₆) in the enantioselective addition of formaldehyde tert-butylhydrazone to prochiral α-keto esters catalyzed by a sugar-based chiral thiourea. Reactions performed in the presence of low percentages of RTILs led to an increase of the catalyst activity, thereby making possible to work at lower temperatures. Thus, the chiral tert-butyl azomethyl tertiary alcohols could be obtained with moderate to good conversions and higher enantioselectivities for most of the studied substrates when using up to 30 vol% of [hmim]PF₆ as a cosolvent in processes performed in toluene.