Science China Materials最新文献

Oxygen vacancies play a vital role in the adsorption, activation, and subsequent reduction of CO₂ to methanol. This work presents the preparation of two-dimensional Bi₂WO₆ nanosheets with different oxygen vacancy concentrations (BWO-OV1, BWO-OV2, and BWO-OV3) and the evaluation of their catalytic activity in the photothermal catalytic reduction of CO₂ to methanol. The oxygen vacancy concentration has played a decisive role in controlling the methanol yield. The BWO-OV2 catalyst with the highest oxygen vacancy concentration (13.9%) accomplishes the maximum methanol yield (82.45 µmol/(g h)). This is because the oxygen vacancies enhance the adsorption and activation of CO₂ in the form of CO₂⁻, broaden the light adsorption range, and promote light-induced charge carrier separation. Also, BWO-OV2 exhibits 1.91 and 3.28 times higher catalytic activity in CO₂ reduction while being used under photothermal catalytic conditions than being employed under photocatalytic and thermal catalytic conditions, respectively. In line with the in-situ Fourier transform infrared spectroscopy and computational analysis, the external heat indiscriminately promotes the adsorption and further conversion of all involved intermediates but the light irradiation selectively enhances the adsorption of CO₂⁻, HCOO*, and CH₃O* species. The findings of the present work might provide key mechanistic insights into understanding the role of thermal and light irradiation in photothermal catalysis.

Magnetically responsive scaffolds are extensively utilized in tissue engineering for their ability to simulate dynamic three-dimensional (3D) cell microenvironment in a rapid, reversible, and contactless manner. However, existing magnetic scaffolds struggle to provide tunable dynamic compression comparable to natural tissues due to the weak magnetism of magnetic nanoparticles and the mechanical brittleness of hydrogels. Here, we propose a biomimetic 3D magnetic scaffold offering tunable and stable magnetically induced compression for dynamic 3D cell culture. By employing hard magnetic particles NdFeB@SiO₂ and a mechanically stable elastomer, Ecoflex, the scaffold achieves 15% compression in the magnetic field (240 mT). Moreover, this magnetic scaffold demonstrates remarkable deformation and mechanical stability during 4000 compression cycles. The magnetic scaffold exhibits stiffness (0.78 kPa) and viscoelasticity (relaxation time of 17 s) similar to adipose tissue. Notably, it is verified that human adipose-derived stem cells (hADSCs) are successfully cultured in this magnetic scaffold and the proliferation of hADSCs can be modulated by magnetically induced dynamic compression. This magnetic scaffold for dynamic 3D cell culture can be potentially utilized in cell biology and tissue engineering.

Machine learning (ML) has been widely used to design and develop new materials owing to its low computational cost and powerful predictive capabilities. In recent years, the shortcomings of ML in materials science have gradually emerged, with a primary concern being the scarcity of data. It is challenging to build reliable and accurate ML models using limited data. Moreover, the small sample size problem will remain long-standing in materials science because of the slow accumulation of material data. Therefore, it is important to review and categorize strategies for small-sample learning for the development of ML in materials science. This review systematically sorts the research progress of small-sample learning strategies in materials science, including ensemble learning, unsupervised learning, active learning, and transfer learning. The directions for future research are proposed, including few-shot learning, and virtual sample generation. More importantly, we emphasize the significance of embedding material domain knowledge into ML and elaborate on the basic idea for implementing this strategy.

The advancement of a Z-scheme photoelectrochemical (PEC) system for hydrogen production and water splitting holds significant promise in addressing the escalating global energy crisis. In this study, a ternary Co-ZnCdS-BiFeO₃ Z-scheme composite photocatalyst was used. By optimizing the ratio of BiFeO₃/ZnCdS, the photocatalytic activity of the material is enhanced, while enhancing the electron transfer efficiency and strengthening the stability of the photoelectric cathode. The Co(dmgBF₂)2(H₂O)₂ was selected as the co-catalyst to further improve the electron-hole separation efficiency and photocorrosion resistance. Under visible light irradiation, the hydrogen production rate of the PEC system can reach 4.03 mmol g⁻¹ h⁻¹. Under optimal conditions, applying a bias voltage of −0.1 V vs. RHE can produce −38.5 µA cm⁻². The photocatalytic current density of is as high as 13 times that of pure ZnCdS, greatly improving the hydrogen production efficiency and stability of the photocatalyst. The study offers a novel benchmark for the development of a high efficiency Z-scheme photocatalyst designed for water splitting and provides new insights into intrinsic resistance through PEC analyses.

Synthetic control of metal oxide nanocrystals with precise size and morphology is of great importance for promising optoelectronic applications due to their unique size- and shape-dependent optical/optoelectronic properties. Nevertheless, the understanding of the mechanism for size and morphology control of metal oxide nanocrystals are less studied. Here, we demonstrate that acetic acid, the byproduct of the initial chemical reaction of precursors, plays a dominate role in determining the morphology of indium oxide (In₂O₃) nanocrystals by influencing the nucleation of the nanocrystals formation. Sufficient acetic acid would induce anisotropic growth, leading to the generation of nanoflowers, while limited existence of acetic acid results in sphere-shaped nanocrystals. Furthermore, the effects of geometries of In₂O₃ nanocrystals on their plasmonic properties are studied. The resulting plasmonic In₂O₃ nanocrystals show size-tunable plasmon resonance peaks in the near-infrared to mid-infrared regime and outstanding air/thermal stability. Our work shall give an in-depth understanding of the mechanism for geometry control of nanocrystals and offer more opportunities in potential optoelectronic and photothermal applications based on plasmonic metal oxide nanocrystals.

Highly pathogenic-resistant bacteria infections seriously hinder the wound healing process and induce a catastrophic threat to human health. Incorporating multiple antibacterial strategies into nanostructured materials has been verified to possess paramount promise for ameliorating therapeutic efficiency against resistant bacteria. Herein, a multifunctional yolk–shell nanocomposite (Au@HCN) comprised of an aurum (Au) core and hollow carbon nanosphere (HCN) shell was prepared via one-step copolymerization and carbonization. The electron plunder by Au@HCN on the bacterial membrane leads to bacterial membrane depolarization and enhanced reactive oxygen species (ROS) metabolism, resulting in remarkable efficacy against drug-resistant bacteria under dark conditions. Moreover, the synergetic photothermal therapy (PTT) displayed significant antibacterial properties (∼98%) when exposed to near-infrared (NIR) irradiation in vitro. Meanwhile, efficient eradication of drug-resistant bacteria in the infected wound in vivo was observed under NIR exposure, thereby promoting wound healing through the prominent antibacterial properties of Au@HCN. The yolk–shell Au@HCN possesses tremendous potential for combating multidrug resistance with high efficiency.

Untreated urea-rich wastewater exerts severe adverse impacts on both the environment and human health, prompting extensive attention towards the urea oxidation reaction (UOR) as a sustainable technology to generate clean energy in recent years. UOR has a thermodynamic advantage over oxygen evolution reaction (OER) (1.23 V vs reversible hydrogen electrode, RHE) and only requires 0.37 V (vs RHE), which is considered as an effective alternative to H₂ production by water electrolysis. However, the inevitable kinetic slowness and complex adsorption/desorption during process, hindering its practical application. Most traditional catalysts utilized for the UOR are comprised of precious metals, resulting in limited economic viability. Inspired by natural ureases, Ni-based catalysts have emerged as promising alternatives owing to their rich deposits, low cost, and the regulated d orbitals of transition metal Ni, demonstrating considerable potential for UOR. Currently, numerous studies have explored Ni-based hydroxides, oxides, chalcogenides, and phosphides in alkaline solutions. In this review, we will explore the UOR reaction mechanism and summarize the catalyst design strategies of various Ni-based catalysts recently, especially Ni-MOF, which has been rarely discussed before. Then, the broad prospects of UOR in practical applications are summarized. Finally, based on the design strategies and performance comparisons discussed above, the challenges and prospects facing the future development of Ni-based electrocatalysts for the UOR will be presented.

A sustainable nitrogen fixation industrial chain centered around nitrate has been proposed in recent years, incorporating advanced techniques such as electro/photo-catalytic nitrate reduction for ammonia and the co-reduction of nitrate and CO₂ for urea production. However, nitrate production heavily relies on energy-intensive processes, which necessitate high-temperature and high-pressure conditions, leading to significant energy consumption and greenhouse gas emissions. So, electrocatalytic nitrogen oxidation is receiving increasing attention as a novel pathway for nitric acid production. Herein, we summarize the recent developments of N₂ oxidation reactions with a focus on their design, mechanism, and catalytic kinetics regulation. Based on the results discussed, we briefly present the current challenges and propose several future opportunities.

Narrowband circularly polarized luminescence (CPL) is a crucial parameter for high color purity display but rarely studied. However, it is rather challenging and significant to provide a route towards high-dissymmetry CPL with both persistent chiroptical stability and narrowband emission. Despite possessing a very narrowband emission and excitation from the unique f-f transition of electrons, the chiral rare earth complexes often racemize with the low inversion barrier, resulting in an undesirable decrease of CPL signal. Herein, we report a circularly polarized Förster resonance energy transfer (C-FRET) in a liquid crystal (LC) coassembly that contains axially chiral alkoxy binaphthyl (R/S-BN) as donor and narrowband emission-featured rare earth Eu(III) complex (EuOL) as acceptor. These highly ordered helical superstructures enable achiral EuOL to emit ultra-dissymmetric CPL, accompanying with a high dissymmetry factor up to 1.44 from LC microcavity resonance. The EuOL@R/S-BN exhibits extremely CPL narrowband with full width at half maximum of 10.8 nm. Compared with the direct excitation, the specific C-FRET strategy in LC coassembly can indirectly emit the highly dissymmetric and narrowband CPL, and completely overcome the CPL weakness from the essential chiral racemization of rare earth Eu(III) complexes. Such LC C-FRET strategy can guarantee the chiroptical stability, high dissymmetry and narrowband emission, which is anticipated to put forward a new route toward the further utilization of rare earth and advanced display technology.