Comparative study of the effect of incorporation of vinylene linkages on the electronic structures of heterocyclic polymers

Using theab initioband structure results of double-zeta quality of polythiophene (PTP), polyfuran (PFU) and polyacetylene (PA), the effects of incorporation of varying percentages of vinylene units on the electronic structures and conduction properties of PTP and PFU have been investigated using a negative-factor counting method in the tight-binding approximation. Both periodic and aperiodic distributions of vinylene units have been studied. The results show that the incorporation of vinylene units makes the heterocyclic polymers better conductors of electricity both intrinsically as well as extrinsically and that the effects are more pronounced for the aperiodic distribution than for the periodic distribution.     

Separation of hydrogen from steam using a SiC-based membrane formed by chemical vapor deposition of triisopropylsilane

A silicon carbide-based membrane was formed in the macropores of an α-alumina support tube by chemical vapor deposition of triisopropylsilane at 700–800°C with a forced cross-flow through the porous wall. The membrane permeated gases except H₂O mainly by the Knudsen diffusion mechanism at permeation temperatures of 50–400°C. The H₂/H₂O selectivity was near or below unity because of the hydrophilic nature of the membrane. After a heat-treatment in Ar at 1000°C for 1 h, however, the membrane formed at a final evacuation pressure of 1 kPa exhibited a H₂/H₂O selectivity of 3–5, for a mixed feed of H₂–H₂O–HBr system, associated in a thermochemical water-splitting process. The H₂ permeance was (5–6)×10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at 50–400°C. The membrane maintained the H₂/H₂O selectivity for more than 100 h in the H₂–H₂O–HBr mixture at 400°C.     

Porous Core–Shell CuCo2S4 Nanospheres as Anode Material for Enhanced Lithium-Ion Batteries

Porous core–shell CuCo₂S₄ nanospheres that exhibit a large specific surface area, sufficient inner space, and a nanoporous shell were synthesized through a facile solvothermal method. The diameter of the core–shell CuCo₂S₄ nanospheres is approximately 800 nm„ the radius of the core is about 265 nm and the thickness of the shell are approximately 45 nm, respectively. On the basis of the experimental results, the formation mechanism of the core–shell structure is also discussed. These CuCo₂S₄ nanospheres show excellent Li storage performance when used as anode material for lithium-ion batteries. This material delivers high reversible capacity of 773.7 mA h g⁻¹ after 1000 cycles at a current density of 1 A g⁻¹ and displays a stable capacity of 358.4 mA h g⁻¹ after 1000 cycles even at a higher current density of 10 A g⁻¹. The excellent Li storage performance, in terms of high reversible capacity, cycling performance, and rate capability, can be attributed to the synergistic effects of both the core and shell during Li⁺ ion insertion/extraction processes.     

Growth factor functionalized biodegradable nanocellulose scaffolds for potential wound healing application

Cellulose - Nanocellulose has been highlighted as one of the most promising biomaterials for biomedical applications with the potential to outperform conventional polymeric materials. However, the...     

Interface contact and modulated electronic properties by external vertical strains and electric fields in graphene/MoS2 heterostructure

Based to the first-principles calculations, we study the electronic properties of graphene/MoS₂ heterostructure by modulating the vertical strains and applying external electric field. Graphene/MoS₂ heterostructure is a van der Waals heterostructure (vdWH) with the interlayer spacing is 3.2 Å for the equilibrium state, and the contact property of the interface is n-type Schottky contact. The Schottky barrier height (SBH) changes with vertical strains which induces a change of charge transfer between graphene and MoS₂ layer. In addition, with strain or without strain, the applied positive electric field can effectively promote the charge transfer from graphene to MoS₂, while the negative electric field has the opposite effect. These findings support for the design of field effect transistors based on graphene vdWHs.     

Sub-10 nm V2O5 Crystals on Carbon Nanosheets for Advanced All-Solid-State Lithium Metal Batteries

V₂O₅, as a lithium-free cathode material, has inherent defects such as sluggish kinetics and volume change and, at the same time, requires a lithium metal anode that tends to form dendrites in liquid electrolytes. Both the lithium dendrite and the flammable electrolyte solvent bring longtime safety issues. This work introduces nonflammable inorganic–organic composite solid electrolyte to inhibit the growth of the lithium dendrite and suppress the instability caused by V₂O₅ nanometerization. However, the long-term cycling and rate performances are still insufficient even when reducing V₂O₅ size to about 50 nm. As an improvement, sub-10 nm V₂O₅/C nanosheets are designed and prepared using corn stalks as precursors through simple impregnation and calcination process. The V₂O₅/C offers a much better electrode/electrolyte contact and interface stability than bulk V₂O₅ and commercial V₂O₅ in the inorganic–organic composite solid electrolyte. The discharge capacity is 228 mAh g⁻¹ at 0.1 C after 50 cycles and ≈110 mAh g⁻¹ at 2.0 C.     

红外光谱在高分子物理实验教学中的应用*

将红外光谱应用于高分子物理实验教学,通过一些实例阐述了红外光谱在聚合物鉴别、分子构象、结晶度以及相容性表征等方面的应用。该实验的设置可以使学生充分了解红外光谱分析的原理方法,学会使用该方法表征高分子不同尺度的结构,激发学生的学习热情,培养学生综合利用所学知识分析和解决问题的能力。     

High Performance Bifunctional Electrocatalysts Designed Based on Transition-Metal Sulfides for Rechargeable Zn–Air Batteries

Due to the energy crisis by the excessive consumption of fossil fuels, Zinc–air batteries (ZABs) with high theoretical energy density have attracted people‘s attention. The overall performance of ZABs is largely determined by the air cathode catalyst. Therefore, it is necessary to develop high-efficiency and low-cost bifunctional catalysts to replace noble metal catalysts to promote the development of ZABs. Among a variety of cathode catalysts, TMS has become a research hotspot in recent years because of its better electrical conductivity than metal phosphides and metal oxides. In this work, we focus on the means of improving the electrocatalytic performance of transition-metal sulfides (TMS) providing ideas for us to rationally design high-performance catalysts. Furthermore, the performance improvement law between catalyst performance and ZABs is also discussed in this work. Finally, some challenges and opportunities faced in the research of TMS electrocatalysis are briefly proposed, and strategies for improving the performance of ZABs are prospected.     

Synthesis and characterization of photorefractive polymers containing indole groups

Some new photorefractive polymers containing indole groups were synthesized and characterized by IR, ¹H NMR, and UV techniques. The Gibbs free energy changes (ΔG) of corresponding reactions were predicted by density functional theory to be 4.19 and ?9.71 kcal mol^?1 for –H, and 4.12 and ?11.93 kcal mol^?1 for –OCH₃, respectively. The glass transition temperature (T _g) of the polymers were about 96–111 °C. The nonlinear second-order optical susceptibility was predicted to be 2.84 × 10^?30 and 1.04 × 10^?30 esu by theoretical quantum calculations.     

Preparation and characterization of In2O3/ZnO heterostructured microbelts by sol–gel combined with electrospinning method

Long and thin In₂O₃/ZnO heterostructured microbelts were synthesized by sol–gel combined with electrospinning process. The as-prepared microbelts show the well defined one-dimensional belt structures with 1–5 μm in width and tens of millimeters in length. The polycrystalline microbelts calcined at 973 K for 1 h are still continuous and have the uniform rectangular cross sections and the thickness to width ratio is around 1:10. The crystalline phases of samples are investigated by X-ray diffraction and the morphology is examined using transmission electron microscope and scanning electron microscope. In₂O₃/ZnO heterostructured microbelts exhibit the excellent visible photocatalytic property in the photodegradation of methyl orange (MO), and over 94 % of MO was degraded within 3 h.