Composites of small Ag clusters confined in the channels of well-ordered mesoporous anatase TiO2 and their excellent solar-light-driven photocatalytic performance

Small Ag clusters confined in the channels of ordered mesoporous anatase TiO2 have been fabricated via a vacuum-assisted wet-impregnation method, utilizing well-ordered mesoporous anatase TiO2 with high thermal stability as the host. The composites have been characterized in detail by X-ray diffraction, X-ray photoelectron spectroscopy X-ray absorption fine structure （XAFS） spectroscopy, N2 adsorption, UV-visible diffuse reflectance spectroscopy and transmission electron microscopy. The results indicate that small Ag clusters are formed and uniformly confined in the channels of mesoporous TiO2 with an obvious confinement effect. The presence of strong AgO interactions involving the Ag clusters in intimate contact with the pore walls of mesoporous TiO2 is confirmed by XAFS analysis, and favors the separation of photogenerated electron-hole pairs, as shown by steady-state surface photovoltage spectroscopy and transient-state surface photovoltage measurements. The ordered mesoporous Ag/TiO2 composites exhibit excellent solar-light-driven photocatalytic performance for the degradation of phenol. This is attributed to the synergistic effects between the small Ag clusters acting as traps to effectively capture the photogenerated electrons, and the surface plasmon resonance of the Ag clusters promoting the absorption of visible light. This study clearly demonstrates the high-efficiency utilization of noble metals in the fabrication of high-performance solar-light-driven photocatalysts.     

铝合金熔焊微气孔的三维同步辐射X射线成像

基于同步辐射X射线成像技术,对激光复合焊7020-T651铝合金接头内部的微气孔进行了研究,对气孔的体积、圆整度、扁平度及气孔形心至自由表面的距离等三维特征参数进行了统计分析与拟合.结果表明,铝合金熔焊微气孔主要为近球形的冶金型气孔,圆整度在0.65以上,以焊缝中心近似呈现对称分布,且焊缝上部气孔尺寸较大,热影响区和下部气孔密集且尺寸较小.等效直径在20 mm范围内的气孔,在接头上部和下部的频率分别高达65%和85%,并且100 mm以上的大尺寸气孔较少见.此外,由于熔池的下塌倾向和快速凝固,残留于枝晶网络间液相导致焊缝下部形成垂直于焊缝且层叠分布的形状复杂的热裂纹,少部分气孔之间以及气孔和热裂纹之间存在着连通现象,从而使得下部微气孔的圆整度平均值变小.此外,焊接速率越大,整个接头内部气孔体积分数越小,但对气孔形貌和位置的分布影响并不明显.     

Investigation of the hydriding kinetic mechanism in the MgH2/Cr2O3-nanocomposite

A kinetic analysis was done in the nano-MgH₂ and MgH₂/Me_xO_y-nanocomposite (Me_xO_y=V₂O₅, Cr₂O₃ and Fe₃O₄) using a new kinetic model proposed recently in our group. The summarized data of hydriding rate are very well fitted using the new model, and it indicates that the rate-controlling step is the hydrogen diffusion through the hydride phase. Compared with the characteristic absorption time of these nano-MgH₂ and MgH₂/Me_xO_y-nanocomposite, the difference in the kinetic property was investigated in an explicit analytic form and the order of reaction rate and the optimal amount of oxide catalyst Cr₂O₃ can be determined exactly. These facts support that our model is reasonable in the nano-MgH₂ and MgH₂/Me_xO_y-nanocomposite system.     

In-Situ Electrochemically Activated Surface Vanadium Valence in V2C MXene to Achieve High Capacity and Superior Rate Performance for Zn-Ion Batteries

Vanadium-based materials are fascinating potential cathodes for high energy density Zn-ion batteries (ZIBs), due to their high capacity arising from multi-electron redox chemistry. Most vanadium-based materials suffer from poor rate capability, however, owing to their low conductivity and large dimension. Here, we propose the application of V₂C MXene (V₂CT_x), a conductive 2D nanomaterial, for achieving high energy density ZIBs with superior rate capability. Through an initial charging activation, the valence of surface vanadium in V₂CT_x cathode is raised significantly from V²⁺/V³⁺ to V⁴⁺/V⁵⁺, forming a nanoscale vanadium oxide (VO_x) coating that effectively undergoes multi-electron reactions, whereas the inner V-C-V 2D multi-layers of V₂CT_x are intentionally preserved, providing abundant nanochannels with intrinsic high conductivity. Owing to the synergistic effects between the outer high-valence VO_x and inner conductive V-C-V, the activated V₂CT_x presents an ultrahigh rate performance, reaching 358 mAh g⁻¹ at 30 A g⁻¹, together with remarkable energy and power density (318 Wh kg⁻¹/22.5 kW kg⁻¹). The structural advantages of activated V₂CT_x are maintained after 2000 cycles, offering excellent stability with nearly 100% Coulombic efficiency. This work provides key insights into the design of high-performance cathode materials for advanced ZIBs.     

Blue light-emitting diodes based on halide perovskites: Recent advances and strategies

Metal halide perovskites, as a new generation of semiconductor materials, have been widely applied in various optoelectronic devices, especially in the field of perovskite light-emitting diodes (PeLEDs). The external quantum efficiencies (EQEs) of green, red, and near-infrared PeLEDs have exceeded 20% for the last few years, which are comparable to those of the state-of-the-art organic light-emitting diodes (OLEDs) and quantum-dot light-emitting diodes (QLEDs). However, the performances of blue PeLEDs lag far behind those of their counterparts, presumably due to the low quantum yields of blue perovskite films, the instability of the emission spectra, and the difficulties in charge injection for the devices under operation conditions. In this review, the structures and physical properties of blue emissive perovskite materials and the preparation methods of the corresponding perovskite films are firstly addressed. Then, the recent advances and strategies to improve the efficiency of blue PeLEDs are outlined, and the main challenges faced with the blue PeLEDs are also discussed. Finally, an outlook on blue LEDs based on perovskite materials is proposed.     

Nanostructured Ni3Al layers and Ni3Al/Ni multilayers obtained by magnetron sputtering

Intermetallic Ni₃Al thin layers and Ni₃Al/Ni multilayers were deposited on a Si wafer by means of magnetron sputtering. The structure and morphology of the layers have been characterized by X-ray diffraction, transmission electron microscopy and atomic force microscopy. The polycrystalline films are textured in the (111) direction and have grain sizes below 20 nm. Superlattice reflections due to chemical order have been observed in the electron microscope. It is shown by x-ray diffraction that the multilayers grow coherently on the amorphous substrate.     

Synthesis and characterization of reactive ladderlike polyallylsilsesquioxane and polyvinylsilsesquioxane

Ordered reactive ladderlike polyallylsilsesquioxane (hereafter referred to as Allyl-T) and polyvinylsilsesquioxane (hereafter Vi-T) were synthesized via stepwise coupling polymerization. During this reaction, coupling agent p-phenylenediamine (PDA) is supposed to act as a template which enables silane molecules to self-assemble through strong hydrogen-bonding interaction between Si–OH groups and N–H groups. The structure of the polymers was characterized by IR, X-ray diffraction, DSC, GPC, ¹H-NMR, ¹³C-NMR and ²⁹Si-NMR. The data show that the two polymers have ordered ladderlike molecular structure. Hence, the stepwise coupling polymerization is suitable to synthesize ladderlike polysilsesquioxanes (LPSs) containing grafted reactive vinyl-terminated groups.     

High-Temperature Oxidation Behavior and Oxide Scale Structure of Yttrium-Modified Ni–16Mo–7Cr–4Fe Superalloy at 1273 K

Oxidation of Metals - Oxidation of a Ni–16Mo–7Cr–4Fe superalloy containing various yttrium concentrations (0.00, 0.05, 0.12, 0.21 and 0.43 wt%) was undertaken in air at...     

Enhanced degradation of lignin in corn stalk by combined method of Aspergillus oryzae solid state fermentation and H2O2 treatment

To shorten the time of corn stalk pretreatment and increase the degradation of lignin, solid state fermentation (SSF) with Aspegillus oryzae CGMCC5992 in the presence of H₂O₂ was carried out to degrade lignin in stalk. In this study, the conditions for lignin hydrolysis catalyzed by enzymes produced in SSF for 10 days were optimized by mono-factor-at-a-time design and response surface method (RSM). The removal rate of lignin increased from 30% (before hydrolysis) to 80.3% (after hydrolysis) under the temperature of 55 ^°C, pH 6.0, water/stalk ratio of 40, and the concentration of H₂O₂ at 4% (w/w). In comparison, the removal rate of lignin after 50 days of SSF only reached 57.8%. Proteomic analysis provided support for the increased lignin hydrolysis. Fermentation with A. oryzae CGMCC5992 in the presence of H₂O₂ increased the amount of peroxidase and intracellular catalase and decreased the amount of extracellular catalase. Therefore, the method introduced in this study can significantly shorten the time of SSF and increase the removal rate of lignin.     

Self‐Assembly of Poly‐Adenine‐Tailed CpG Oligonucleotide‐Gold Nanoparticle Nanoconjugates with Immunostimulatory Activity

Synthetic unmethylated cytosine–guanine (CpG) oligodeoxynucleotides (CpG ODNs) possess high immunostimulatory activity and have been widely used as a therapeutic tool for various diseases including infection, allergies, and cancer. A variety of nanocarriers have been developed for intracellular delivery of CpG ODNs that are otherwise nonpermeable through the cellular membrane. For example, previous studies showed that gold nanoparticles (AuNPs) could efficiently deliver synthetic thiolated CpG ODNs into cultured cells and induce expression of proinflammatory cytokines. Nevertheless, the necessity of using thiolated CpG ODNs for the modification of AuNPs inevitably complicates the synthesis of the nanoconjugates and increases the cost. A new approach is demonstrated for facile assembly of AuNP‐CpG nanoconjugates for cost‐effective drug delivery. It is found that non‐thiolated, diblock ODNs containing a CpG motif and a poly‐adenine (polyA) tail can readily self‐assemble on the surface of AuNPs with controllable and tunable density. Such nanoconjugates are efficiently delivered into RAW264.7 cells and induce immune response in a Toll‐like receptor 9 (TLR9)‐dependent manner. Under optimal conditions, polyA‐CpG‐AuNPs show significantly higher immunostimulatory activity than their thiolated counterpart. In addition, the immunostimulatory activity of CpG‐AuNPs can be modulated by varying the length of the polyA tail. In vivo induction of immune responses in mice is demonstrated by using polyA‐tailed CpG‐AuNP nanoconjugates.