Search

Imine-linked covalent organic frameworks (COFs) provide distinctive prospects for promoting photocatalytic H2O2 production, yet the intricate involvement of imine-derived linkages chemistry under light irradiation remains incompletely elucidated. Here, imine-linked COF-LZU1 demonstrates a visible light-driven H2O2 evolution rate of 387 ​μmol ​g−1 ​h−1, particularly, negligible dependence on the sacrificial agents. By virtue of electron paramagnetic spectroscopy and solid-state nuclear magnetic resonance, we experimentally tracked the structure evolution and identified its autooxidation to Wurster's salt mimics under the photocatalytic conditioning. This finding coincides with the radical anion ·O2− governed reaction pathway and is further rationalized with additional theoretical calculations. This study provides insights into both photophysical/photochemical aspects over the imine-linkage structure.

Advanced photovoltaics, such as ultra-flexible perovskite solar cells (UF-PSCs), which are known for their lightweight design and high power-to-mass ratio, have been a long-standing goal that we, as humans, have continuously pursued. Unlike normal PSCs fabricated on rigid substrates, producing high-efficiency UF-PSCs remains a challenge due to the difficulty in achieving full coverage and minimizing defects of metal halide perovskite (MHP) films. In this study, we utilized Al2O3 nanoparticles (NPs) as an inorganic surface modifier to enhance the wettability and reduce the roughness of poly-bis(4-phenyl) (2,4,6-trimethylphenyl) amine simultaneously. This approach proves essentials in fabricating UF-PSCs, enabling the deposition of uniform and dense MHP films with full coverage and fewer defects. We systematically investigated the effect of Al2O3 NPs on film formation, combining simulation with experiments. Our strategy not only significantly increases the power conversion efficiency (PCE) from 11.96% to 16.33%, but also promotes reproducibility by effectively addressing the short circuit issue commonly encountered in UF-PSCs. Additionally, our UF-PSCs demonstrates good mechanical stability, maintaining 98.6% and 79.0% of their initial PCEs after 10,000 bending cycles with radii of 1.0 and 0.5 ​mm, respectively.

Co-catalysts decorations provide unique opportunity in promoting the photocatalytic water splitting performance of graphite carbon nitride (g-C3N4) system, while mechanistic understanding of this complex catalytic network remains elusive. Here, taking the single-atom-based photocatalysts (M1-g-C3N4) as an unprecedented simplified model system, we theoretically tracked the photocatalytic kinetics for a comprehensive understanding of the photocatalytic process and afforded the descriptor αS1-T1/αT1-S0 (ratio of the extent of S1-T1 and T1-S0 state mixing) and ΔGH∗ (hydrogen adsorpti on free energy) for rational screening of photocatalysts. The targeted Fe1-g-C3N4 yields an excellent H2 evolution rate (ca. 3.2 ⋅mmol·gcat−1·h−1 under full arc), two order of magnitude improvement relative to pristine g-C3N4 counterpart and also outperforms other representative 3d-transition-metal-based photocatalysts. This work presents a comprehensive understanding of the essential role of isolated atomic sites in the photocatalytic course and sheds light on the design of photocatalysts from both photophysical and photochemical aspects.

We develop two discrete models to study how supplemental releases affect the Wolbachia spreading dynamics in cage mosquito populations. The first model focuses on the case when only infected males are released at each generation. This release strategy has been proved to be capable of speeding up the Wolbachia persistence by suppressing the compatible matings between uninfected individuals. The second model targets the case when only infected females are released at each generation. For both models, detailed model formulation, enumeration of the positive equilibria and their stability analysis are provided. Theoretical results show that the two models can generate bistable dynamics when there are three positive equilibrium points, semi-stable dynamics for the case of two positive equilibrium points. And when the positive equilibrium point is unique, it is globally asymptotically stable. Some numerical simulations are offered to get helpful implications on the design of the release strategy.

Serious carrier recombination and limited active sites are the main restrictions on the efficiency of CO2 photoconversion over g-C3N4-based photocatalysts. Herein, a unique tubular C3N4-carbon heterostructure was constructed via thermal polycondensation process, where the inherent open porous C3N4 microstructure was rationally exploited as scaffolds to co-assemble with pyridinic N moieties into composites. Beyond the critical role of serving as a carbon source, the EDTA-2Na additive provides a fairly straightforward pathway for the production of surface cyano groups, which presumably results from the dehydration process of amide bonds. The interfacial cyano groups and work function difference induce strong built-in electric field effects, boosting spatial carrier transfer kinetics. Meanwhile, the incorporated reactive N species endow high affinity for CO2 and thereby remarkable enhancement of uptake capacity. The developed hybrid system modulates the CO2 reduction pathway with favoured 8e− selectivity (56%) toward CH4 products, with an evolution rate up to 2.54 μmol·g-1 h−1, compared with trace of the bare C3N4 counterpart. This work constitutes a prospective target for surface and interface design and paves the way for developing high-performance photocatalysts for multi-electron CO2 reduction.

Operational stability and mechanical robustness remain as engineering bottlenecks in perovskite solar cells technology. Here, Dong et al. introduce an interpenetrating perovskite at the electron-transporting-layer interface that enables a 1000-hour stable operation and high endurance against bending fatigue over 2500 cycles.

In this article, we formulate and study a discrete equation model depicting the pattern of Wolbachia infection in a mosquito population. A domain in $\mathcal {R}_+^2 $ is called a Wolbachia infection enhancing (or decaying) domain if in which the Wolbachia infection frequency of the next generation is always bigger (or smaller) than that of the current generation. We first give a complete analysis of the equivalent Wolbachia infection frequency curves. And then we clearly characterize the Wolbachia infection enhancing domain and decaying domain for all of the parameters, respectively. Finally, some numerical examples are also provided to illustrate our theoretical results.

Abstract Background To analyze the relative expression of PELI3 and its mechanistic involvement in the non-small cell lung cancer (NSCLC). Methods PELI3 expression in NSCLC tissue samples was determined by the immunohistochemistry. The transcripts abundance of PELI3 was measured with real-time PCR. The protein intensity was analyzed by western blot. The overall survival in respect to PELI3 or miR-365a-5p expression was plotted by the Kaplan–Meier’s analysis. Cell growth was determined by colony formation assay. Cell viability was measured by MTT assay. The migration and invasion were evaluated by wound healing and transwell assay respectively. The regulatory effect of miR-365a-5p on PELI3 was interrogated with luciferase reporter assay. The direct binding between miR-365a-5p and PELI3 was analyzed by pulldown assay. Results PELI3 was aberrantly up-regulated in NSCLC both in vivo and in vitro. High level of PELI3 associated with poor prognosis. PELI3-deficiency significantly inhibited cell viability, colony formation, migration and invasion. We further identified that miR-365a-5p negatively regulated PELI3 in this disease. Ectopic expression of miR-365a-5p in both A549 and H1299 phenocopied PELI3-deficiency. Meanwhile, PELI3-silencing significantly abolished the pro-tumoral effect elicited by miR-365a-5p inhibition. Conclusion Our results highlighted the importance of dysregulated miR-365a-5p-PELI3 signaling axis in NSCLC.

In order to explore the axial electromagnetic dynamic balance force curve of a scroll compressor under the action of thermal energy, radial clearance, mechanism friction, and other factors in actual working conditions, an axial force exploration method that can automatically approach sections is proposed in this paper. Considering the dynamic response ability of the electromagnetic balance system, an automatic optimization algorithm of the partition number was proposed to find the optimal partition number in order to achieve the optimal tracking effect. An experimental platform was built to test the effect of the segmented tracking method on calibrating the deviation between the theoretical axial force curve and the real curve. The results show that the curve construction method proposed in this paper has convergence. This method can automatically and accurately construct the axial balance force curve required by the electromagnetic dynamic balance. Through the automatic optimization algorithm, the standard error (RMSE) between the target curve and the theoretical curve was reduced from 290 to 22.6, and the number of partitions with the lowest standard error was 20. The results provide a useful reference for the accurate, automatic, and efficient exploration of the actual axial sealing force of the scroll compressor.

In this work, we investigate the existence and stability of periodic orbits of a mosquito population suppression model based on sterile mosquitoes. The model switches between two sub-equations as the actual number of sterile mosquitoes in the wild is assumed to take two constant values alternately. Employing the Poincaré map method, we show that the model has at most two T-periodic solutions when the release amount is not sufficient to eradicate the wild mosquitoes, and then obtain some sufficient conditions for the model to admit a unique or exactly two T-periodic solutions. In particular, we observe that the model displays bistability when it admits exactly two T-periodic solutions: the origin and the larger periodic solution are asymptotically stable, and the smaller periodic solution is unstable. Finally, we give two numerical examples to support our lemmas and theorems.

The non-classical oriented attachment crystallization pathway explains the growth of many nanocrystals. Here, the authors study citrate-stabilized gold nanoparticles by in-situ liquid transmission electron microscopy to reveal that surface ligands are a critical driving force in the oriented attachment process.

To control the spread of mosquito-borne diseases, one goal of the World Mosquito Program’s Wolbachia release method is to replace wild vector mosquitoes with Wolbachia-infected ones, whose capability of transmitting diseases has been greatly reduced owing to the Wolbachia infection. In this paper, we propose a discrete switching model which characterizes a release strategy including an impulsive and periodic release, where Wolbachia-infected males are released with the release ratio α1 during the first N generations, and the release ratio is α2 from the (N+1)-th generation to the T-th generation. Sufficient conditions on the release ratios α1 and α2 are obtained to guarantee the existence and uniqueness of nontrivial periodic solutions to the discrete switching model. We aim to provide new methods to count the exact numbers of periodic solutions to discrete switching models.

Imine-linked covalent organic frameworks (COFs) provide distinctive prospects for promoting photocatalytic H2O2 production, yet the intricate involvement of imine-derived linkages chemistry under light irradiation remains incompletely elucidated. Here, imine-linked COF-LZU1 demonstrates a visible light-driven H2O2 evolution rate of 387 μmol g-1 h-1, particularly, negligible dependence on the sacrificial agents. By virtue of electron paramagnetic spectroscopy and solid-state nuclear magnetic resonance, we experimentally tracked the structure evolution and identified its autooxidation to Wurster's salt mimics under the photocatalytic conditioning. This finding coincides with the radical anion ·O2- governed reaction pathway and is further rationalized with additional theoretical calculations. This study provides insights into both photophysical/photochemical aspects over the imine-linkage structure. [ABSTRACT FROM AUTHOR]

Advanced photovoltaics, such as ultra-flexible perovskite solar cells (UF-PSCs), which are known for their lightweight design and high power-to-mass ratio, have been a long-standing goal that we, as humans, have continuously pursued. Unlike normal PSCs fabricated on rigid substrates, producing high-efficiency UF-PSCs remains a challenge due to the difficulty in achieving full coverage and minimizing defects of metal halide perovskite (MHP) films. In this study, we utilized Al2O3 nanoparticles (NPs) as an inorganic surface modifier to enhance the wettability and reduce the roughness of poly-bis(4-phenyl) (2,4,6-trimethylphenyl) amine simultaneously. This approach proves essentials in fabricating UF-PSCs, enabling the deposition of uniform and dense MHP films with full coverage and fewer defects. We systematically investigated the effect of Al2O3 NPs on film formation, combining simulation with experiments. Our strategy not only significantly increases the power conversion efficiency (PCE) from 11.96% to 16.33%, but also promotes reproducibility by effectively addressing the short circuit issue commonly encountered in UF-PSCs. Additionally, our UF-PSCs demonstrates good mechanical stability, maintaining 98.6% and 79.0% of their initial PCEs after 10,000 bending cycles with radii of 1.0 and 0.5 mm, respectively. [ABSTRACT FROM AUTHOR]

In this study, association between zinc (II) and dipicolylamine was studied by isothermal titration calorimetry. At neutral of weakly alkaline conditions, with zinc (II) in cell and dipicolylamine in syringe, increasing heat release was observed as the titration proceeded. Considering the equilibrium between Zn2+ and Zn(OH)2 at these conditions, the increasing heat release is ascribed to the increasing solubilization of colloidal Zn(OH)2 followed by neutralization of OH- by the buffer. Though quantitative determination of the increase in solubility is not accomplished, to the best of our knowledge, this is the first report about solubility increase of colloidal zinc hydroxide using calorimetric method. [ABSTRACT FROM AUTHOR]

Infrared dyes in dye-sensitized solar cells (DSCs) usually mismatch with the band structure of TiO2. This mismatch subsequently results in insufficient kinetics in charge separation. Researchers have started focusing on ternary oxide semiconductors because of their stability. Moreover, the chemical compositions and band structures of these semiconductors are easy to control. In this paper, a ternary semiconductor oxide, Zn2SnO4, was synthesized through a hydrothermal method and used as a photoanode for DSCs. Zn2SnO4 selectivity toward organic and ruthenium complex dyes was different from that of TiO2. Zn2SnO4-DSCs performance was improved at a greater degree with organic sensitizer 2-cyano-3- {4-[2-(4- diphenylamino-phenyl)-vinyl]-phenyl}-acrylic acid (TPC) than with cis-bis (isothiocyanato)-bis (2,2-bipyridyl- 4,4-dicarboxylato) ruthenium (II) bis-tetrabutyl-ammonium (N719). We further improved the power conversion efficiency of Zn2SnO4- DSCs to 5.72% through surface modification and structural optimization. Stepped light-induced measurement of photocurrent and photovoltage was used to systematically study electron behaviors in surface-modified and unmodified Zn2SnO4- based and TiO2-based DSCs. Zn2SnO4 exhibited higher electron diffusion coefficient than TiO2. The electron lifetime of Zn2SnO4-based DSCs increased after surface modification. [ABSTRACT FROM AUTHOR]

We report an effective method for mass production of ZnO hierarchical flowers (HFs) that are constructed by interlaced single crystalline ZnO nanosheets with dominant surfaces of (1120) and (1100). The size of ZnO HFs, thickness and parking density of the nanosheets, and HF inner porosity can be tuned by changing the synthesis conditions. The HFs containing porous inner structures showed an excellent performance as the photoanode material in quasi-solid (using polymer gel electrolytes) dye-sensitized solar cells (DSCs) because of their superior optical and electrical properties. The high current density (10.26mAcm-2) and efficiency (4.93%) of the HF-based DSCs indicate a great potential for the development of high-efficient quasi-solid DSCs. [ABSTRACT FROM AUTHOR]

The interface modification effect within quasi-solid dye-sensitized solar cells and the photovoltaic performance were investigated after the introduction of Mg(OOCCH3)2 as an additive into a polymer gel electrolyte. Electrochemical impedance spectroscopy showed that the addition of Mg(OOCCH3)2 into the polymer gel electrolyte can efficiently retard charge recombination at the TiO2/electrolyte interface. Mg(OOCCH3)2 in the electrolyte can also contribute to the enhancement of the incident photon-to-electron conversion efficiency by modifying the dye molecules. This results in an improvement in the photovoltage and photocurrent due to a barrier layer at the TiO2/electrolyte interface and the promotion of charge injection at the dye/TiO2 interface, respectively. Photovoltaic measurements reveal that a conversion efficiency enhancement from 4.05% to 4.96% under 100 mW cm-2 is obtained after the amount of Mg(OOCCH3)2 added was optimized. [ABSTRACT FROM AUTHOR]

The high efficiency of perovskite solar cells benefits from the high density of photoinduced free carriers. We studied how exciton and free carriers, as the two major photoproducts, coexist inside the CH3NH3PbI3 perovskite. A new density-resolved spectroscopic method was developed for this purpose. The density-dependent coexistence of excitons and free carriers over a wide density range was experimentally observed. The quantitative analysis on the density-resolved spectra revealed a moderate exciton binding energy of 24 ± 2 meV. The results effectively proved that the strong ionic polarization inside the perovskite has a negligible contribution to exciton formation. The spectra also efficiently uncovered the effective mass of electron-hole pairs. Our spectroscopic method and the results profoundly enrich the understanding of the photophysics in perovskite materials for photovoltaic applications. [ABSTRACT FROM AUTHOR]