Oriented self-assembly of anisotropic layered double hydroxides (LDHs) with 2D-on-3D hierarchical structure

Layered double hydroxides (LDHs) have been the subject of increasing research due to their unique 2D or 3D structures and promising applications. However, achieving precise control over their morphology and architecture has proven to be a significant challenge. In this work, we present an oriented self-assembly strategy for the synthesis of ultrathin 2D-on-3D CoNi-LDHs nanoflowers (NFs) at ambient temperature. Ex situ and in situ characterization techniques were employed to elucidate the formation process of the 2D-on-3D CoNi-LDHs hierarchical structure. The 2D nanosheets are composed of CoNi(OH)2 seeds that undergo rapid nucleation and growth. Under the influence of oriented attachment and Ostwald ripening, the 2D nanosheets continue to crystallize along the axial and radial directions, resulting in the formation of 2D-on-3D CoNi-LDH NFs. This unique 2D-on-3D LDHs structure possesses an ultrathin thickness of approximately 1.5 nm, nanopores with a diameter of approximately 3.8 nm, and a large surface area of approximately 154 m2/g. These properties manifest excellent energy-storage performance in supercapacitors. Our approach provides important insights into the precise synthesis of LDHs with a 2D-on-3D hierarchical structure. The synthesis of LDHs with well-defined structures is a significant challenge in materials science. Our work contributes to the advancement of this field and has the potential to facilitate the development of new, high-performance energy-storage devices.publishedVersio

The <i>MKK2a</i> Gene Involved in the MAPK Signaling Cascades Enhances <i>Populus</i> Salt Tolerance

Mitogen-activated protein kinase (MAPK) cascades are highly conserved signal transduction modules, which transmit environmental signals in plant cells through stepwise phosphorylation and play indispensable roles in a wide range of physiological and biochemical processes. Here, we isolated and characterized a gene encoding MKK2 protein from poplar through the rapid amplification of cDNA ends (RACE). The full-length PeMKK2a gene was 1571 bp, including a 1068 bp open reading frame (ORF) encoding 355 amino acids, and the putative PeMKK2a protein belongs to the PKc_like (protein kinase domain) family (70–336 amino acids) in the PKc_MAPKK_plant subfamily and contains 62 sites of possible phosphorylation and two conserved domains, DLK and S/T-xxxxx-S/T. Detailed information about its gene structure, sequence similarities, subcellular localization, and transcript profiles under salt-stress conditions was revealed. Transgenic poplar lines overexpressing PeMKK2a exhibited higher activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) than non-transgenic poplar under salt stress conditions. These results will provide insight into the roles of MAPK signaling cascades in poplar response to salt stress

Experimental Study on the Effects of Heavy Metal Pollution on Soil Physical Properties and Microstructure Evolution

Soil heavy metal pollution poses a formidable challenge for environmental protection professionals. This study delves into the impact of zinc and lead pollution on the particle size distribution, liquid-plastic limit, permeability, shear strength, and other pertinent physical and engineering properties of clay. The alterations in the microstructure of soil contaminated by heavy metals were scrutinized using a scanning electron microscope. The findings reveal that as the concentration of heavy metals in contaminated soil rises, there is a concurrent decrease in the liquid limit, plasticity index, and silt content. This, in turn, leads to the deterioration of the original fluidity and plasticity of the soil, accompanied by a reduction in fine particles. Resistivity tests indicate that an escalation in water content results in a decrease in resistivity, an increase in porosity leads to an increase in resistivity, and an elevation in the concentration of heavy metals precipitates a sharp decline in resistivity due to the heightened conductivity of heavy metal ions. Heavy metal pollution induces structural changes in the soil, particularly in pore size, thereby influencing the permeability coefficient

Highly Efficient and Exceptionally Durable CO₂ Photoreduction to Methanol over Freestanding Defective Single-Unit-Cell Bismuth Vanadate Layers

Unearthing an ideal model for disclosing the role of defect sites in solar CO₂ reduction remains a great challenge. Here, freestanding gram-scale single-unit-cell <i>o</i>-BiVO₄ layers are successfully synthesized for the first time. Positron annihilation spectrometry and X-ray fluorescence unveil their distinct vanadium vacancy concentrations. Density functional calculations reveal that the introduction of vanadium vacancies brings a new defect level and higher hole concentration near Fermi level, resulting in increased photoabsorption and superior electronic conductivity. The higher surface photovoltage intensity of single-unit-cell <i>o</i>-BiVO₄ layers with rich vanadium vacancies ensures their higher carriers separation efficiency, further confirmed by the increased carriers lifetime from 74.5 to 143.6 ns revealed by time-resolved fluorescence emission decay spectra. As a result, single-unit-cell <i>o</i>-BiVO₄ layers with rich vanadium vacancies exhibit a high methanol formation rate up to 398.3 μmol g^–1 h^–1 and an apparent quantum efficiency of 5.96% at 350 nm, much larger than that of single-unit-cell <i>o</i>-BiVO₄ layers with poor vanadium vacancies, and also the former’s catalytic activity proceeds without deactivation even after 96 h. This highly efficient and spectrally stable CO₂ photoconversion performances hold great promise for practical implementation of solar fuel production