Preparation and photocatalytic properties of biomorphic hierarchical WO3 based on bionic rice hull

Research on Chemical Intermediates - In this study, biomorphic WO3-Cx nanomaterial was successfully prepared with rice hull as biological templates. The structure and morphology of the nanomaterial...     

Micro/Nanoengineered α-Fe2O3 Nanoaggregate Conformably Enclosed by Ultrathin N-Doped Carbon Shell for Ultrastable Lithium Storage and Insight into Phase Evolution Mechanism

The Fe-based transition metal oxides are promising anode candidates for lithium storage considering their high specific capacity, low cost, and environmental compatibility. However, the poor electron/ion conductivity and significant volume stress limit their cycle and rate performances. Furthermore, the phenomena of capacity rise and sudden decay for α-Fe₂O₃ have appeared in most reports. Here, a uniform micro/nano α-Fe₂O₃ nanoaggregate conformably enclosed in an ultrathin N-doped carbon network (denoted as M/N-α-Fe₂O₃@NC) is designed. The M/N porous balls combine the merits of secondary nanoparticles to shorten the Li⁺ transportation pathways as well as alleviating volume expansion, and primary microballs to stabilize the electrode/electrolyte interface. Furthermore, the ultrathin carbon shell favors fast electron transfer and protects the electrode from electrolyte corrosion. Therefore, the M/N-α-Fe₂O₃@NC electrode delivers an excellent reversible capacity of 901 mA h g⁻¹ with capacity retention up to 94.0 % after 200 cycles at 0.2 A g⁻¹. Notably, the capacity rise does not happen during cycling. Moreover, the lithium storage mechanism is elucidated by ex situ XRD and HRTEM experiments. It is verified that the reversible phase transformation of α↔γ occurs during the first cycle, whereas only the α-Fe₂O₃ phase is reversibly transformed during subsequent cycles. This study offers a simple and scalable strategy for the practical application of high-performance Fe₂O₃ electrodes.     

The antidepressant effect of 4-hydroxybenzyl alcohol 2-naphthoate through monoaminergic,GABAergic system and BDNF signaling pathway

Abstract

Gastrodigenin, also known as 4-hydroxybenzyl alcohol (HBA), is one of the main components of Gastrodia elata, which is a perfect lead compound of natural products. In order to get new active compounds, we modified the structure of HBA through esterification with carboxylic acid, and got a series of derivatives in which 4-hydroxybenzyl alcohol 2-naphthoate (NHBA) showed stronger antidepressant activity than HBA. In this paper, we firstly evaluated the antidepressant activity of NHBA by tail suspension test (TST) and forced swimming test (FST). Then, we carried out the biochemical assay and western blot to determine its mechanism. The results displayed that NHBA could increase the content of serotonin, dopamine, norepinephrine, γ-aminobutyric acid, brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB) in mice brain. It suggested that NHBA exhibited an antidepressant-like effect through monoaminergic system, GABAergic system and BDNF/TrkB signaling pathways.     

白色荧光粉CaF2∶Yb3+/Eu3+/La3+的制备及其上转换发光特性

采用改进的两步高温固相熔融法制备了Yb^3+、Eu^3+、La^3+共掺杂CaF 2的上转换荧光粉。基于荧光猝灭原理,通过改变La^3+掺杂浓度来调节CaF 2∶Yb^3+/Eu^3+材料的发光性能,并在980 nm近红外光激发下,获得了该材料的白色上转换发光(UCL)。在该发光体系中,Yb^3+不仅起到了敏化Eu^3+的作用,同时,Yb^3+二聚体(Yb^3+-dimer)自身合作发出波长范围480~540 nm的绿色荧光。而白光三基色中的绿光正是来自Yb^3+二聚体的合作发光。Eu^3+则作为激活剂,同时发出红色和蓝色荧光。荧光寿命测试结果表明Yb^3+-dimer与Eu^3+之间存在有效的能量传递。值得注意的是,在980 nm激光激发下,1%La^3+掺杂的样品表现出最佳的红、绿、蓝三基色光比列,实现了材料的上转换白光发射,其色度坐标为(0.311,0.340)。     

正电子冲击下氦电离三重微分截面的理论计算

我们发展了一种正电子碰撞原子电离的畸变波Born近似方法， 在这个方法中，正负电子偶素通道通过一个ab initio的光学势附加到入射粒子和靶的相互作用势上，且通道对电离作用被第一次被考虑在正电子碰撞原子电离的过程中. 应用这个方法计算了在50 eV入射能量范围氦的电离的三重微分截面，计算结果和实验数据很好的符合.     

First principles study on the structural,electronic and phonon properties of monolayer B2Si

Using first principles density functional theory, we predict a monolayer B₂Si structure with space group Pmm2 in the present work. This structure is confirmed to be dynamically stable. Based on the plane wave pseudopotential approach, the charge density, electron localization function, density of states, energy band, phonon property and thermal conductivity of Pmm2-B₂Si are systematically studied. It is interesting that the sp² hybridization and coordination bond of Si are found in Pmm2-B₂Si, which is the most important factor for its structural stability. The density of states and energy band analysis reveals that Pmm2-B₂Si is metallic because of the partial occupied Si 3pz and B 2pz states. Moreover, the acoustic-optical coupling is important for phonon transport in Pmm2-B₂Si, and the contribution of optical modes to the lattice thermal conductivity along the [100] and [010] directions is 13% and 12%, respectively. This study gives a fundamental understanding of the structural, electronic and phonon properties in Pmm2-B₂Si.     

Semiconducting Polymer Dots with Dual-Enhanced NIR-IIa Fluorescence for Through-Skull Mouse-Brain Imaging

Fluorescence probes in the NIR-IIa region show drastically improved imaging owing to the reduced photon scattering and autofluorescence in biological tissues. Now, NIR-IIa polymer dots (Pdots) are developed with a dual fluorescence enhancement mechanism. First, the aggregation induced emission of phenothiazine was used to reduce the nonradiative decay pathways of the polymers in condensed states. Second, fluorescence quenching was minimized by different levels of steric hindrance to further boost the fluorescence. The resulting Pdots displayed a fluorescence QY of ca. 1.7 % in aqueous solution, suggesting an enhancement of ca. 21 times in comparison with the original polymer in tetrahydrofuran (THF) solution. Small-animal imaging by using the NIR-IIa Pdots exhibited a remarkable improvement in penetration depth and signal to background ratio, as confirmed by through-skull and through-scalp fluorescent imaging of the cerebral vasculature of live mice.     

Rapid and Scalable Access to Sequence-Controlled DHDM Multiblock Copolymers by FLP Polymerization

An immortal N-(diphenylphosphanyl)-1,3-diisopropyl-4,5-dimethyl-1,3-dihydro-2H-imidazol-2-imine/diisobutyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum (P(NIⁱPr)Ph₂/(BHT)AlⁱBu₂)-based frustrated Lewis pair (FLP) polymerization strategy is presented for rapid and scalable synthesis of the sequence-controlled multiblock copolymers at room temperature. Without addition of extra initiator or catalyst and complex synthetic procedure, this method enabled a tripentacontablock copolymer (n=53, k=4, dp_n=50) to be achieved with the highest reported block number (n=53) and molecular weight (M_n=310 kg mol⁻¹) within 30 min. More importantly, this FLP polymerization strategy provided access to the multiblock copolymers with tailored properties by precisely adjusting the monomer sequence and block numbers.