Modulate the Strong Exciton Effect by Na+ Coordination-Induced Trap States: Efficient Photocatalytic H2O2 Production.

Due to the strong Coulomb interaction, in most polymer photocatalysts, electron-hole pairs exist in the form of excitons rather than free charge carriers. The giant excitonic effect is a key obstacle to generating free charge carriers. Therefore, effectively regulating the exciton effect is the first step to achieving optimized carrier separation. Here, we used C-ring/g-C3N4 as the prototypical model system to design a photocatalyst with a Na-coordination-induced trap state. We demonstrate that the excitons can be effectively dissociated into charge carriers by combining with the trap state formed by Na doping sites. Encouragingly, signals from the dissociation of excitons into carriers were observed by ultrafast transient spectroscopy. Benefiting from the enhanced exciton dissociation, Na-C/CN displayed a H2O2 production rate of 17.4 mmol·L-1·h-1 with an apparent quantum efficiency up to 26.9% at 380 nm, which is much higher than many other g-C3N4-based photocatalysts. This work explains the effect of cation doping on the exciton-carrier behavior in polymers. Also, it provides a new way to regulate the exciton effect.

Interfacial Chemical Bond Engineering in a Direct Z-Scheme g-C3N4/MoS2 Heterojunction.

The Z-scheme heterojunction shows great potential in photocatalysis due to its superior carrier separation efficiency and strong photoredox properties. However, how to regulate the charge separation at the nanometric interface of heterostructures still remains a challenge. Here, we take g-C3N4 and MoS2 as models and design the Mo-N chemical bond, which connects exactly the CB of MoS2 and VB of g-C3N4. Thus, the Mo-N bond could act as an atomic-level interfacial "bridge" that provides a direct migration path of charge carriers between g-C3N4 and MoS2. Experiments confirmed that the Mo-N bond and the internal electric field promote greatly the photogenerated carrier separation. The optimized photocatalyst exhibits a high hydrogen evolution rate that is about 19.6 times that of the pristine bulk C3N4. This study demonstrates the key role of an atomic-level interfacial chemical bond design in heterojunctions and provides a new idea for the design of efficient catalytic heterojunctions.

Flexible on-chip droplet generation, switching and splitting via controllable hydrodynamics.

Flexible droplet preparation and manipulation are significant for lots applications such as immunoreaction and monocellular culture. Herein, we present a novel method for effective on-chip droplet generation, splitting and switching via controllable hydrodynamics. The microchannel of the designed chip has 6 inlets and 3 three outlets. The water solution is injected from a specific inlet (inlet d), and the other 5 inlets are used to inject oil fluids. Under the shearing effect of immiscible oils, the water phase breaks into dispersed droplets first, and the generated droplets can be further split into daughter drops or switched into side outlets from the middle outlet. To investigate the hydrodynamic droplet manipulation behaviors, a two-dimensional simulation model based on phase-field method is established. Utilizing the computational model, we systematically analyze the influences of the flow rates of continuous and dispersed fluids and the manipulation modes on droplet generation, splitting and switching. The numerical results indicate that the droplets can be generated with controlled sizes. For instance, at Qd = 5 µL/min and Qc1,2 = 5 µL/min, the droplet diameter decreases from 89.2 µm to 49.2 µm as Qs1,2 gradually rises from 15 µL/min to 40 µL/min. Moreover, the prepared droplets can realize on-demand splitting and switching. When Qd, Qc1,2, and Qs1,2 are fixed at 5 µL/min, 5 µL/min and 25 µL/min, respectively, the generated droplet is split into different proportional daughter drops with the rising of Qs3 (or Qs4) at first, and finally it is switched into the side-outlets when Qs3 (or Qs4) is higher than 80 µL/min. Therefore, this proposed droplet manipulation approach will be promising for various applications, and the numerical simulations can provide useful guidelines on the design and operation of droplet-based microfluidic systems.

Covalently Silane-Functionalized Antimonene Nanosheets and Their Copolymerized Gel Glasses for Broadband Vis-NIR Optical Limiting.

Two-dimensional antimonene has many potential applications for its high mobility, high stability, and tunable band gap. The covalent chemistry of antimonene and the molecular doping or hybrid of antimonene remain incomplete for further applications. In this work, silane-functionalized antimonene nanosheets and their copolymerized organically modified silicate gel glasses are designed and prepared. The experimental data confirmed that 3-glycidoxypropyltrimethoxysilane interacts covalently with antimonene. Compared with unfunctionalized antimonene, the silane-functionalized antimonene shows higher concentration, higher compatibility, and dispersion stability in solvents and gel matrices. In particular, the doping concentration of functionalized antimonene nanosheets can reach 2% in gel glass, which is larger than conventional nanocomposites and nanohybrids. These nanosheets exhibit outstanding optical limiting performance in the visible and long-wavelength near-infrared regions (532-2150 nm). The mechanism of optical limiting is found to be a combination of nonlinear absorption, nonlinear refraction, and nonlinear scattering. The silane-functionalized antimonene nanosheets and their copolymerized hybrids will be promising materials for optoelectronics, biology, energy, and others.

miR-374 improves cerebral ischemia reperfusion injury by targeting Wnt5a.

To date, studies have demonstrated the potential functions of microRNAs in cerebral ischemia reperfusion (IR) injury. Herein, we established a middle cerebral artery occlusion (MCAO) model in rats and then subjected them to reperfusion to explore the role of microRNA-374 (miR-374) in cerebral IR injury. After reperfusion, the endogenous miR-374 level decreased, and the expression of its target gene, Wnt5a, increased in brain tissues. Intracerebral pretreatment of miR-374 agomir attenuated cerebral damage induced by IR, including neurobehavioral deficits, infarction, cerebral edema and blood-brain barrier disruption. Moreover, rats pretreated with miR-374 agomir showed a remarkable decrease in apoptotic neurons, which was further confirmed by reduced BAX expression as well as increased BCL-2 and BCL-XL expression. A dual-luciferase reporter assay substantiated that Wnt5a was the target gene of miR-374. miR-374 might protect against brain injury by downregulating Wnt5a in rats after IR. Thus, our study provided a novel mechanism of cerebral IR injury from the perspective of miRNA regulation.